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Fungal and Bacterial Abundance in Long-Term No-Till and Intensive-Till Soils of the Northern Great Plains
Soil Science Society of America Journal
Abstract
Abundance of fungi and bacteria in long-term no-till (NT) and intensively tilled (IT) soils in the Northern Great Plains were measured using phospholipid fatty acid analysis (PLFA) to determine if a shift in the relative abundance of fungi and bacteria occurs as the result of conversion to NT Four tillage trials located in four different soil zones were sampled in spring of 2005 and 2006 before the crop was seeded to evaluate the long-term effect of tillage Oil the microbial community. With the exception of one site-year, total, bacterial, and fungal PLFA were greater in NT than IT soils at the soil surface (0- to 5-cm depth) (P < 0.05). Increases ranged from 8 to 202% for total biomass, 26 to 58% for bacteria] biomass, and 0 to 120% for fungal biomass. At one site (Ellerslie) all biomass measurements were greater in IT than NT in 2005 and bacteria] biomass was also greater under IT in 2006. The influence of tillage on microbial biomass was less pronounced with depth. Fungal dominance is commonly assumed under NT, however, our results demonstrate that although biomass of both fungi and bacteria increase in NT the abundance of fungi vs. bacteria was not consistently greater under NT in the soils studied. Further research is needed to determine if fungi may be able to exert a more functionally dominant role in NT soils without an increase in relative abundance.
... Our finding of significantly higher total PLFA concentrations in RT and MT compared to CT in the top layer has been reported by other studies under different climate and soil conditions (Drijber et al. 2000;Helgason, Walley, and Germida 2009;Li et al. 2020). ...
... The latter would indicate more easily available organic matter. One explanation for this contradiction is that even if the litter supports a high microbial biomass per unit of organic matter, the lower physical disturbance due to less tilling slows the rate of organic matter decomposition due to aggregate formation, contributing to the longevity of microorganisms (Beare et al. 1994;Helgason, Walley, and Germida 2009). Thus, the microbial biomass is less active per unit of organic matter. ...
... This is comparable to the bacteria. Accordingly, fungi are not more relevant than bacteria in low-tilled soils, as also reported by van Groenigen et al. (2010) and Helgason, Walley, and Germida (2009). The arbuscular mycorrhizal PLFA biomarker showed the same pattern, perhaps because this marker also can exist in bacteria (Olsson and Lekberg 2022) and therefore could be compromised. ...
Conventional tillage, including ploughing after harvest and/or for seedbed preparation, aims to incorporate crop residues and weeds and to loosen, mix and aerate the soil. However, less beneficial effects, such as a loss of soil organic carbon (SOC), are also associated with intensive tillage. This has made reduced and minimum tillage systems without ploughing increasingly popular in agriculture, contributing to soil health and climate change mitigation. We studied the effects of different tillage systems on chemical and microbial soil properties in a long‐term field experiment established on a fine‐sandy loamy Haplic Chernozem in Fuchsenbigl, Austria, in 1988. The tillage treatments include conventional tillage (CT) with a plough and a cultivator down to 30 cm soil depth, reduced tillage (RT) with a cultivator down to 15 cm two to three times a year, as well as minimum tillage (MT) treated with a rotary driller once a year down to 5–8 cm soil depth. In 2016, a soil sampling campaign was conducted, and alkaline phosphatase, phospholipid fatty acids (PLFAs), and the nitrogen (N) mineralisation potential were analysed along with chemical properties including SOC, active C, total nitrogen (N t ), CAL extractable phosphorus (P CAL ) and potassium (K CAL ). Under MT, these properties were significantly higher compared to CT in 0–10 cm. In deeper soil layers, these parameters showed very few significant differences between the tillage treatments. RT yielded intermediate values but not always significantly different from CT. PLFA indicators significantly correlated with SOC and, even more distinctly, with N t and active carbon. The high ratio of Gram‐positive to Gram‐negative bacteria indicates more recalcitrant organic matter in the top layer in MT than CT.
... As an effective agricultural management practice, no-tillage (NT) decreases soil CO 2 emissions due to lower soil microbial communities and root activities and soil temperature (ST) than those in conventional tillage (CT) [5][6][7]. Nevertheless, some research has suggested that soil CO 2 effluxes are higher in NT due to higher soil water content (SWC) and nutrients in the soil surface [8][9][10][11][12]. Therefore, there is still some dispute about the influence of NT on soil CO 2 effluxes resulting from various phenomena, including soil texture, duration of NT, and crop types. ...
... It was reported that the relationships of SWC and ST with soil CO 2 emissions were different in various soil conditions. In dry soil, SWC was more significant in influencing soil CO 2 effluxes [8]. However, ST accounted for more contribution to the variation in soil CO 2 emissions in wet soil [3,9]. ...
There is still controversy over the influence of no-tillage (NT) on CO2 emissions in farmland soil. Few studies focus on the impact of monitoring hours on the response of soil CO2 emissions to NT. Therefore, an in situ experiment was conducted in maize cropland in the Shandong Yucheng Agro-ecosystem National Observation and Research Station in the North China Plain. The soil CO2 emissions, soil water content (SWC), and soil temperature (ST) were automatically monitored using the morning sampling (MonS) and continuous sampling (multi-hour sampling in one day, DayS) methods during the whole maize growth stages. The results showed that the MonS method decreased the sum of soil CO2 emissions by 146.39 g CO2 m⁻² in the wet year 2018 and increased that by 93.69 g CO2 m⁻² in the dry year 2019 when compared to the DayS method. The influence intensity of NT on soil CO2 effluxes was decreased with the MonS method. In contrast, the MonS method had no significant effect on the differences in SWC between NT and conventional tillage. However, the MonS method increased the variance in ST between NT and conventional tillage by 0.45 °C, which was higher than that with the DayS method (0.20 °C) across years. Compared to the DayS method, the MonS method increased the regression coefficient of soil CO2 emissions with SWC but decreased that with ST. This study is beneficial for reducing the artificial impact of monitoring hours on the data accuracy of soil CO2 effluxes and deepening the understanding of the influence of NT on soil CO2 emissions.
... variations with soil depth) becomes even more pronounced in perennial cropping due to the lack of tillage compared to annual cropping systems that are tilled frequently. Soil nutrient stratification provides a nutrient-rich environment that supports increased microbial biomass near the soil surface (Helgason et al., 2009). Greater soil nutrient stratification has been found in no-tillage systems due to the accumulation of crop residues and nutrients remaining immobile on the soil surface (Lupwayi et al., 2006). ...
... Our results agree with earlier findings in which long-term land cover together with no-tillage practices had been found to increase fungal biomass (Helgason et al., 2009), fungal diversity (Schmidt et al., 2019) and the fungi:bacteria ratio (Sun et al., 2016) due to reduced physical disturbance and disruption of fungal hyphal network development. Soils with low nitrogen availability generally have fungal-based microbial communities and energy channels (Wardle et al., 2004;de Vries and Bardgett, 2012), whereas nitrogen-rich systems have bacterial-based microbial communities and energy channels, which follows the general assumption that nitrogen demand is predicted by the biomass C:N ratio (~5-15 in fungi compared to~3-6 in bacteria) (Strickland and Rousk, 2010;Koranda et al., 2014). ...
... No-tillage with residue application was proved to increase the soil microbial community [162]. In many cases, both bacteria and fungi were more abundant under no-tillage than conventional tillage [163]. In no-tillage systems, fungi domination was frequently found and the residue was mainly decomposed by the fungal community [162]. ...
... In no-tillage systems, fungi domination was frequently found and the residue was mainly decomposed by the fungal community [162]. Bacteria were generally considered to be the predominant decomposers of incorporated crop residues under conventional tillage [163]. However, more information is necessary to understand the effect of different tillage system combined with different residue quantity on soil microbial community. ...
... Tillage systems impact soil physical properties including aggregation, pore size, water holding capacity and bulk density. This significant disturbance to soil as a habitat affects the soil biota, and as a result eventually can change the soil microbial community structure (Helgason et al., 2009;Roger-Estrade et al., 2010). Reducing soil aeration and increasing soil bulk density as a result of compaction can directly affect the soil microbial community by reducing micro-and macropores (Whalley et al., 1995;Li et al., 2002). ...
... However, many studies have concluded that tillage alone may not influence soil microbial community structure. Other contributing agents, e.g., nutrient availability, temporal factors, and spatial scale, may be more influential in regulating the microbial community (Helgason et al., 2009). For example, Spedding et al. (2004) found no significant differences in soil microbial biomass between tilled and no-till plots. ...
Microbial abundance and community structure can be altered directly and indirectly by soil physical and chemical characteristics which, in turn, can be influenced by land use management. This study utilized the cubist model to predict soil microbial communities based on soil properties at different depths and under different agricultural management in Dawson County, Montana, USA. A total of 538 soil samples were collected from three management treatments (control, no-tillage (NT), and no tillage with livestock grazing in winter (NTLS)) from three depths (0–5, 5–15, and 15–30 cm). Soil physical and chemical properties and total phospholipid fatty acid (PLFA) analysis were used to predict soil biological properties. Root mean square error (RMSE), mean absolute error (MAE), relative error (RE), mean bias error (MBE), and R squared (R2) were used to assess the performance of predictions. Results showed that the strongest correlation was between the total PLFA and soil microorganisms. Different soil chemical and physical properties were useful to predict soil microbial communities; ammonium-N, phosphorus, potassium, electrical conductivity, pH, organic matter, bulk density, sand, and clay significantly correlated with most soil microorganisms. Results indicated that the cubist algorithm produced promising results to predict most soil microorganism responses to various treatments and depths. However, this model did not perform well when attempting to predict the ratio of bacteria to fungi. The most important variable to predict all soil microorganisms was the total PLFA, with >90 % effectiveness. These results imply that applying pedotransfer functions (PTFs) to predict soil microbial communities in areas with limited soil data and monetary resources shows promise.
... A decrease in tillage intensity has in some cases led to a shift in the soil microbial community towards fungal dominance (Bhattarai, 2015;Sanaullah et al., 2020), probably due to reduced disruption of the fungal mycelium. On the other hand, several existing studies do not report a promotion of fungi with decreasing tillage intensity (Helgason et al., 2009;Spedding et al., 2004;Strickland and Rousk, 2010); thus, the body of empirical evidence is far from definitive. ...
... Significant soil physical disturbances caused by tillage can create unfavourable conditions for soil fungi. The fungal mycelium can be damaged during the tillage process (Helgason et al., 2009;Hendrix et al., 1986), subsequently reducing fungal abundance in intensively tilled soils (Hydbom et al., 2017;Strickland and Rousk, 2010). Contrarily, better access to substrates and nutrients particularly in the topsoil as well as more favourable microclimatic conditions through conservation tillage practices can additionally benefit soil fungal growth (Kladivko, 2001;Peixoto et al., 2020). ...
The aim of global carbon (C) neutrality brings soils and their potential for C storage into the spotlight. Improved agricultural management techniques such as minimum or no-tillage are thought to foster soil C sequestration. However, the underlying mechanisms are still not well understood. In this study, we investigated the inter-relations of soil organic C (SOC), fungal biomass, microbial necromass biomarkers, and aggregate stability in rhizosphere and bulk soil after thirteen years of reduced tillage intensities (reduced, minimum, and no-tillage). Overall, rhizosphere and bulk soil were indifferent in their response to reduced tillage. Reducing tillage intensity increased SOC and nitrogen stocks and dissolved organic C contents in the following order: minimum > no-tillage > reduced > conventional. Aggregate stability showed the strongest increase under no-tillage. Interestingly, ergosterol contents were highest under reduced and minimum tillage followed by no-tillage. The amino sugars muramic acid, galactosamine, and glucosamine – proxies for soil microbial-derived necromass – showed similar increases under all three tillage reduction systems. Structural equation modelling revealed that increased dissolved organic C contents under reduced tillage intensity facilitated SOC sequestration and aggregate stability through enhanced fungal biomass to necromass turnover. Thus, reducing soil tillage intensity is a valuable tool to facilitate microbial growth and hence to increase SOC sequestration in agricultural soils.
... Tillage causes a large shift diversity of soil microfauna and microflora (Bockus and Shroyer 1998). It has been reported that MT helps preserving the microbiological populations over other intensified tillage regimes (Helgason et al. 2009). For instance, intensified tillage under MBP treatment causes the breakdown of water-stable aggregates (Six et al. 2004) and, therefore, fragments the roots and fungal hyphae that are considered chief gluing agents for the formation of macroaggregates (Bronick andLal 2005, Benbi et al. 2016). ...
Sugarcane (Saccharum officinarum L.) is a commercial cash crop of tropical
and subtropical regions and has a huge demand of plant nutrients. Sugarcane
soils had low- to medium-organic carbon (C), and management practices
largely governs the C gain and losses, thereby influences the soil organic C pool and its dynamics. Its residue (known as trash) is fibrous in nature and rich source of nutrients, and is produced in significant amounts (~7–30 Mg ha−1 of dry mass). Therefore, conservation tillage and residue retention in sugarcane cultivation has significant potential for nutrients’ cycling and C sequestration in soils. Conservation tillage and residue retention potentially increased soil organic C stocks, microbial diversity and population, enzymatic activity and soils’ physical attributes. Sugarcane trash retention significantly influenced soil micro-fauna due to increased nutrients’ concentration in soils. Sugarcane soils had higher value of C management index, an index of soil organic matter stability in soils as compared with the soils under rice–wheat system, indicating C rehabilitation due to sugarcane cultivation. Carbon sequestration in soils under sugarcane cultivation with residue retention/removal was considerably influenced by soil texture; fine texture soil showed greater C accrual than the light textured soils.
... Interestingly, the soil depth of 5-30 cm had 38.6% more bacterial populations than the soil depth of 30-45 cm. As soil depth is a critical factor influencing soil microbial communities, their populations may differ with varying depths (Helgason et al., 2009), and the microbial communities sampled from deeper soil profiles may exhibit distinct characteristics compared to those sampled from the surface of the soil. The decrease in SOC and N at lower depths under no-till systems may be a Long-term effect of tillage and nutrient management practices on microbial (a,b) and (c,d) at tasseling of 9th season maize under maize-mustard rotation. ...
In South Asian regions, the traditional maize–mustard rotation (MMR) has become less profitable and unsustainable due to inappropriate fertilization practices and the degradation of soil properties. Therefore, climate-smart and sustainable farm practices are necessary to mitigate production risks and improve soil properties. This study evaluated the long-term impacts of conservation tillage and nutrient management on equivalent yields, soil microbial properties, and water-energy savings. A long-term field experiment was initiated 9 years ago, using the split-plot design to evaluate the three conservation tillage (CA)-based crop establishment practices, i.e., zero tillage (ZT) and conventional tillage (CT), permanent beds (PNB). Each practice was accompanied by the recommended dose of fertilizer (RDF), improved RDF (RDFI), and nutrient expert-guided (NEI) fertilization. CA-based tillage (ZT or PNB) resulted in 24.4–25.2% greater maize grain equivalent yields (EY) compared to the CT, while the NEI and RDFI produced statistically (p = 0.05) identical EY, being 26.6–30.3% greater than the RDF. These practices substantially reduced the water footprints, besides 11.9–12.9% and 23.4–26.6% (9-yrs average) greater water productivity compared to CT and RDF, respectively. In fact, at 0–45 cm soil depth, residues retained ZT or PNB had 31.9–42.2%, 56.5–67.2%, and 16.5–18.3% more bacterial (10⁷), fungi (10⁴), and actinomycetes (10⁴) populations, respectively. Across soil depths, ZT or PNB recorded 7.65–11% and 23.2–31.9% greater soil microbial biomass-C and -P, respectively. Compared to CT-based practices, these practices also improved soil mineralizable N (NO3⁻ N/NH4⁺ N). The conventionally tilled plots consumed greater direct and indirect non-renewable energy than the CA-based residue-retaining practices. By virtue of residue retention, the PNB and ZT had ~108% greater energy input (EI) than the CT, whereas it was vice versa in terms of the energy output (EO). The NEI registered a 7.6–28.7% higher EO than the RDFI and RDF. These long-term field studies demonstrated that adopting CA-based ZT, or PNB, in combination with precise nutrient management would enhance equivalent yields and soil microbial dynamics, besides improving water-energy footprints in maize–mustard growing ecologies.
... The results of our microbial biomass analysis do not indicate any change under intercropping, though. This may be due to the intensive tillage carried out before and during the experiment which has been shown to reduce fungal biomass in other studies (Helgason et al., 2009;Hydbom et al., 2017). The latter would be expected to be less important than bacterial biomass given the rather high soil pH. ...
Intercropping has been claimed to improve the soil structure and soil quality, however its effects on soil fertility parameters in semi-arid Mediterranean agroecosystems remain unclear. The objective of this study was to assess whether intercropping and its combination with N fertilisation are adequate practices to improve the soil aggregate stability and organic matter quality. An irrigated on-farm experiment was established in northeastern Spain to evaluate the effect of seven cropping systems (faba bean-durum wheat, pea-durum wheat, and rapeseedpea intercropping and the respective sole crops) and two N-fertiliser rates (0 vs. 75 kg N ha-1). Several soil variables were analysed in bulk soil: water-stable macro- and microaggregates, soil organic carbon (SOC), soil total nitrogen (STN), reduced permanganate (Perred), particulate organic matter (POM) and carbon (POC), mineral-associated organic matter (MAOM) and carbon (MAOC) and microbial biomass carbon (MBC) and nitrogen (MBN). Also, SOC, Perred and nitrogen (N) storage within aggregates were determined. Intercropping did not increase the share of water-stable aggregates nor SOC levels, but SOC concentration was higher in macro (2.34 g C 100 g-1) than in microaggregates (1.89 g 100 g-1). Intercropping did also not affect STN, but the mineral N-fertilised treatment increased both SOC (2.24 vs. 2.08 g 100 g-1) and STN (0.193 vs 0.177 g 100 g-1) significantly in bulk soil. This study showed that after a few years upon establishment, intercropping had not enhanced the soil aggregate stability significantly and as a sole practice intercropping does not improve soil C and N concentrations nor their active fractions.
... In line with our expectations, the total abundance of free-living nematodes increased significantly in the NTLM cropping systems (+295 %, Fig. 1a). We attribute these changes to two main mechanisms: (i) the enrichment in soil carbon (Balesdent et al., 2000;Autret et al., 2016) and hence soil microbial biomass (Helgason et al., 2009;Sun et al., 2023) in the superficial soil layer with the presence of a permanent plant cover and no tillage, and (ii) the reduction of soil physical disturbance thanks to the presence of a mulch and no tillage, which favors soil biota in the soil layer (Roger-Estrade et al., 2010;Betancur-Corredor et al., 2022;Coulibaly et al., 2022). ...
Conservation agriculture systems leaning on living mulch show particular promise thanks to their benefits on soil biological activity, but weed pressure in these cropping systems strongly depends on the amount of mulch. To assess the ability of these cropping systems to sustain soil health considering pest regulation, we investigated the combined influence of tillage and crop management (conventional, CONV and no-tillage with living mulch, NTLM) and weeding regimes (weekly hand-weeding and none) on soil free-living and plant-parasitic nematodes. To do so, we leant on a split-plot field experiment in Madagascar highlands 7 years after crop establishment. Overall, the abundance of soil free-living nematodes was 3.9 times higher in NTLM than CONV, primarily due to a preferential increase in fungal-feeders (+585 %) and in omnivores and predators (+633 %). Conversely, plant-parasitic nematodes had the same abundance in both systems, but not the same taxonomic composition, with a dominance of endoparasitic taxa in CONV, and of ectoparasitic taxa in NTLM. Weeding management affected only populations in NTLM, leading to increased abundance of fungal-feeders (+191 %) and lower abundance of semi-endoparasites (− 89 %) in the unweeded systems, which were associated with changes in plant community diversity. In this context, conservation agriculture and no-weeding proved beneficial for promoting free-living nematode communities but also to decrease the overall plant parasitic pressure through plant diversification. As no weeding may nonetheless affect crop yield, a trade-off has therefore to be found to promote soil ecosystem services while maintaining crop production.
... First, the fungal: bacteria ratio is reputedly influenced by several factors, among which soil physical disturbance, nutrient availability and the C:N ratio of soil organic matter, pH or humidity, but the direction of the effect is largely variable (Strickland and Rousk, 2010). Fungi can be expected to be more susceptible to soil physical disturbance than bacteria in terms of abundance, due to the disruption of mycelium (Helgason et al., 2009;Young and Ritz, 2000). As such, fungi could be negatively affected by earthworm bioturbation, which could alter the dense network of hyphae and decrease fungal biomass. ...
... Historically, some of the first studies of tillage impacts on microbes reported that conventional practices decrease both bacterial and fungal biomass. Although it is frequently assumed that conservation tillage favors fungal dominance 19 , recent global meta-analyses do not support this observation 20,21 . Tillage regimes also modify community diversity and composition. ...
As conservation agricultural practices continue to spread, there is a need to understand how reduced tillage impacts soil microbes. Effects of no till (NT) and disk till (DT) relative to moldboard plow (MP) were investigated in a long-term experiment established on Chernozem. Results showed that conservation practices, especially NT, increased total, active and microbial biomass carbon. The effects on diversity measured through amplicon sequencing were greater for prokaryotes than for fungi. NT increased prokaryotic richness at both the lower and the higher taxonomic level, while for both microbial groups it tended to decrease Shannon index at the higher taxonomic level. No differences were observed between DT and MP. Conversely, tillage intensity induced a clear separation of both prokaryotic and fungal communities among all three practices. Comparing abundance of ecologically meaningful groups revealed more abundant saprotrophic fungi in MP and differences in the bacterial groups involved in the N cycle. Differential analysis showed relatively similar numbers of plant growth promoting prokaryotic taxa. However, it also revealed higher numbers of pathogenic fungal taxa that are enriched in NT. Overall, our findings illustrate that tillage changes the structure of both prokaryotic and fungal communities, including distribution of functional groups, without necessarily changing diversity.
... Conservation tillage enhances both fungal and bacterial biomass [24] with NT specifically increasing arbuscular mycorrhizal fungal species richness, evenness, and diversity [25]. Previous research has also highlighted that NT creates a favorable environment with higher soil moisture and moderate temperatures, which promote fungal growth [16,26]. By minimizing soil disturbance, NT preserves the integrity of fungal hyphal networks, leading to greater biomass accumulation under suitable conditions [27]. ...
Conservation tillage and fertilization are widely adopted in agricultural systems to enhance soil fertility and influence fungal communities, thereby improving agroecosystems. However, the effects of no-tillage combined with manure on grain yield, nitrogen use efficiency (NUE), soil fertility, and rhizosphere fungal communities remain poorly understood, particularly in rainfed wheat fields on the Loess Plateau. A 15-year field experiment was conducted at the Niujiawa Experimental Farm of the Cotton Research Institute, Shanxi Agricultural University. Five treatments were assessed: conventional tillage without fertilizer (C), no-tillage with chemical fertilizer (NT), no-tillage with chemical fertilizer and manure (NTM), conventional tillage with chemical fertilizer (T), and conventional tillage with chemical fertilizer and manure (TM). The results demonstrated that the NTM treatment significantly increased grain yield by 124.95%, NT by 65.88%, TM by 68.97%, and T by 41.75%, compared to the C treatment (p < 0.05). NUE in the NTM treatment was improved by 58.73%–200.59%. Compared with the C treatment, NTM significantly enhanced soil nutrients, including organic matter (OM) by 70.68%, total nitrogen (TN) by 8.81%, total phosphorus (TP) by 211.53%, available nitrogen (AN) by 90.00%, available phosphorus (AP) by 769.12%, and available potassium (AK) by 89.01%. Additionally, the NTM treatment altered the rhizosphere fungal community of winter wheat, with Ascomycota (81.36%–90.24%) being the dominant phylum, followed by Mucoromycota (5.40%–12.83%) and Basidiomycota (1.50%–8.53%). At the genus level, NTM significantly increased the abundance of Mortierella and Dendrostilbella. An α-diversity analysis revealed that the richness and diversity of soil fungi were highest under NTM. The unweighted pair-group method with arithmetic mean (UPGMA) and principal coordinates analysis (PCoA) based on Bray-Curtis distances indicated that NTM formed a distinct fungal community with the highest phylogenetic diversity, which differed significantly from other treatments. Redundancy analysis (RDA) demonstrated that soil chemical properties variably influenced fungal community dynamics, with higher abundances of Ascomycota and Zoopagomycota positively correlated with OM, AN, AP, TP, and AK. Correlation analysis showed that wheat yield and NUE were positively correlated with Mortierella and Dendrostilbella, and negatively correlated with Fusarium, Chaetomium, and Alternaria. In conclusion, no-tillage with manure not only enhanced soil fertility but also enhanced soil fungal community structure, leading to greater wheat yield and NUE. These findings provide guidance for agricultural practices in rainfed wheat fields of the Loess Plateau.
... Soil microorganisms are responsible for multiple agroecosystem services including nutrient cycling, pest and disease control and thus soil health and fertility (Bender et al., 2023;Delgado-Baquerizo et al., 2016;Wagg et al., 2021). Several studies have documented the beneficial impacts of reduced tillage practices on increasing the abundance of soil microorganism (Chen et al., 2020;Essel et al., 2019;Helgason et al., 2009;Mathew et al., 2012;Morugán-Coronado et al., 2022). Through the disruption of fungal mycelia, intensive tillage is suspected to negatively impact fungal communities especially the symbiotic arbuscular mycorrhizal fungi (AMF). ...
... In addition, high SOC content provides more favorable environmental conditions for the microbial communities by improvement of soil aggregation, moisture, and proper soil temperature which can lead to an increase in microbial abundance (Helgason, Walley, & Germida, 2009;X. Zhang et al., 2018). ...
... Tillage and residue-management practices directly impact crop productivity [49], and our findings also reveal variations in the grain yields of both rice and wheat across different tillage and residue-management treatments. Moreover, the higher wheat grain yields in all residue-management treatments during wheat cultivation under the direct-seeded rice (DSR) system of rice sowing compared to the puddled transplanting rice (PTR) system [50] align with the functional microbial diversity indices, which also showed higher values under the DSR system compared to the PTR system [51]. ...
The sustainable productivity of rice–wheat cropping systems relies on soil health, and soil health can be positively influenced by treating previous crop residues using conservation tillage practices. The present study examined the impact of three rice residue-management practices under zero-tilled wheat (ZTW) and conventionally tilled wheat (CTW), along with two rice-sowing practices, during rice cultivation on soil functional microbial diversity, physiological profiling, and grain yields of rice and wheat. Anchored residues (ARs) under ZTW exhibited significantly (p ≤ 0.05) high average well color development—31.43% more than CTW with no residue (NR). CTW with residue burning (BUR) showed a 5.42% increase in the Shannon diversity index compared to CTW-NR. Substrate richness was 10.02% higher in CTW-BUR compared to CTW-NR. CTW-BUR demonstrated the highest 17.98% increase in the Shannon evenness index compared to CTW-NR. The direct-seeded rice (DSR) system generally surpassed puddled transplanted rice (PTR) in most indices, except for the Shannon evenness index values. ZTW-AR exhibited the highest utilization of amino acids, carboxylic acids, and phenolic compounds, while CTW-BUR exhibited the highest utilization of carbohydrates and polymers utilization, and ZTW with no-residue (NR) exhibited the highest utilization of amines. Rice and wheat grain yields were highest with full residue in ZTW and lowest in CTW-NR. PTR supported higher rice yields, while DSR was superior for wheat. These findings highlight the favorable role of residue retention with no tillage during wheat cultivation in the maintenance of soil quality and rice–wheat productivity.
... Indeed, it has been demonstrated from previous studies that low or excessive doses of fertilisation could produce negative or no effects on plant growth (Battipaglia et al. 2023). This suppressive effect might be due to an interplay of negative factors such as the alteration of the chemical, biological, and physiological nature of soil (Helgason et al. 2009;Lauber et al. 2013;Yang et al. 2018), the properties of the rhizosphere, the root exudate cycle, and root turnover rate (Menyailo et al. 2002;Prescott and Grayston 2013;Scheibe et al. 2015). Finally, compost fertilisation did not interfere with the ring width pattern and magnitude. ...
An accurate investigation is needed to determine if the selected location, the tree species, and the applied treatments can support a successful seedling establishment and outplanting performance to ensure the success of large-scale tree-planting initiatives. To shed light on the growth pattern of the trees used in the Green Belt Project plantations in the Mongolian steppe, we analysed the biomass allocation in the stem and roots of Ulmus pumila in terms of ring width, considering different management techniques involving irrigation and fertilisation. We found that the root and shoot ring width of U. pumila followed a bell-shaped curve and reached maximum values after three or four years from seedling outplanting. Moreover, our data confirm that increasing watering regimes may enhance plant growth, especially the root system, while fertilisation did not show a positive effect independently of the fertilisation type (i.e. NPK and compost). Our data allowed us to develop a predictive regression model that could be used with other species and in different environmental conditions to forecast stem and root tree growth and to simulate afforestation performances in different climatic conditions.
... On the one hand, the increase of carbon sequestration potential under no-tillage practice may only be limited to the topsoil (0-10 cm) (Luo, Wang, and Sun 2010). Under no-tillage, crop residues were not incorporated into the soil, which reduces the contact with soil particles and leads to less susceptibility of residues to microbial breakdown in the deeper layer (20-40 cm) (Helgason, Walley, and Germida 2009). On the other hand, when the amount of crop residues is too high, the excessive residues on the soil surface decrease the utilization of oxygen by microorganisms, which is not conducive to the degradation of residues (Lupwayi et al. 2004). ...
Tillage and straw returning are promising practices to improve soil quality, especially because of the unclear controlling effects on microbial communities and functions. A 5‐year field experiment in a winter wheat‐summer maize cropping system was implemented in the North China Plain to address this research gap. Management practices were deep tillage, rotary tillage, and no‐tillage, each with either wheat only or both wheat and maize straw returning. Shotgun metagenomic sequencing was performed to investigate the microbial community, diversity, co‐occurrence network, and function in the topsoil (0–20 cm). The associations between soil physiochemical properties and microbial community characteristics were also evaluated. Rotary tillage with only wheat straw returning (RTS) significantly increased Shannon's diversity index by 0.24%–1.71% compared to other treatments. No‐tillage with only wheat straw returning (NTS) showed the most stable microbial network with the highest betweenness centrality (199.09), average path distance (2.31), and modularity (0.50). NTS had the highest relative abundance of microbial carbon (C), nitrogen (N) metabolisms, and C fixation pathways. Among deep tillage practices, both wheat and maize straw returning (DTD) were more beneficial to the stability of microbial networks than only wheat straw returning (DTS), yet without improvement in microbial diversity and function. In conclusion, microbial community and function are practical predictors of variations in soil nutrient availability, and pH value in response to different tillage and residue management practices. In particular, our study provides a basis for the development of a sustainable crop residue management system.
... For example, fungi are thought to be more tolerant to drought than bacteria mainly due to their chitinous cell walls (Bapiri et al., 2010;Curiel-Yuste et al., 2011). However, agricultural practices, such as tillage, usually have a greater impact on fungal abundance than bacteria due to the disruption of fungal mycelium (Helgason et al., 2009). Moreover, bacteria mainly regulate the fast carbon cycling pathways in soil, while fungi are mainly involved in the degradation of recalcitrant organic matter (Kirchman, 2012;Rousk & Bååth, 2007). ...
Land abandonment promotes forest expansion into abandoned agricultural lands in Europe. This process leads to changes that affect several ecosystem services, but it is considered a low‐cost strategy to restore soil functions in past agricultural lands. Soil microbial communities play a key role in restoring functions. However, the relationship among forest expansion, microbial communities, and soil functioning is unclear.
In this study, we used a Juniperus thurifera expansion gradient on abandoned agricultural lands in Alto Tajo National Park (Spain) to discover the changes elicited by the soil microbial communities and their functions along this gradient considering two microhabitats, under the canopy and open areas. Specifically, our objectives were (i) to analyse how soil properties (organic matter and pH), microbial communities (using PLFAs‐NFLAs) and enzymatic activities (related to C, N and P cycling) varied along the forest expansion gradient and between microhabitats and (ii) to decipher the pathways by which soil properties control the carbon and nutrient cycling in soils.
The forest expansion gradient had a direct negative effect on phosphatase activity. The microhabitat showed a positive direct effect on organic matter content, pH, actinomycetes and arbuscular mycorrhizal fungi biomass and on soil C and P cycling. Moreover, the biomass of gram‐positive bacteria determined the biomass of other microbial groups.
Synthesis and Applications: Though its effectiveness is variable, passive restoration can be more effective than active restoration. Our research indicates that passive tree colonisation of past agricultural land is enough to achieve soil functionality similar to a mature forest for most variables studied. However, some variables would need more time to reach mature forest levels, such as total microbial biomass and organic matter content. Therefore, to support ecosystem recovery, the management of this applied forest ecology strategy requires continuous monitoring of newly established trees and soil to elucidate the time needed to achieve mature soil properties.
... Found that NT compared to conventional tillage (CT) reduces soil physical disturbance and enriches organic matter at the soil surface, enhancing conditions for microbial life. NT showed higher total phospholipid fatty acids (PLFAs), indicating increased microbial biomass, particularly for fungi and bacteria (Helgason et al., 2009). However, NT also led to lower MUFA/STFA ratios, suggesting more anaerobic conditions (Bossio et al., 1998). ...
Soil microorganisms are essential for nutrient cycling, organic matter decomposition, and pollutant detoxification, playing a vital role in ecosystem stability and soil health. This review examines the impact of agricultural practices and environmental factors on soil microbial communities and the consequent biological degradation. Intensive agriculture, characterized by monocropping and heavy use of chemical fertilizers, leads to reduced microbial diversity and activity, disrupting nutrient cycles and impairing soil fertility. Studies indicate that sustainable practices such as organic farming, conservation agriculture, and crop rotations enhance microbial activity, improve soil structure, and boost crop yields. Agroforestry systems and the use of organic amendments have shown higher microbial and enzymatic activities compared to traditional monocropping. Additionally, environmental disturbances like deforestation, mining, and fires significantly reduce microbial biomass and alter community structures, further degrading soil health. Mitigation strategies, including zero tillage and residue retention, are effective in combating biological degradation and improving soil health. This review underscores the need for sustainable land management practices to preserve soil microbial diversity, enhance soil fertility, and ensure long-term agricultural productivity. Future research should focus on promoting strategies that support microbial activity and contribute to the sustainability of agroecosystems.
... The small dots represent the composition at each site, while the large dots correspond to the compositional geometric means for each land use. (maíz: 1 año LC, papa: dos años consecutivos de LC) puede deberse a que durante el proceso de labranza, el micelio fúngico puede dañarse (Helgason et al. 2009), lo que provoca una disminución de la abundancia fúngica en los suelos intensamente laboreados (Hydbom et al. 2017) y una reducción de la presencia de los nematodos fungívoros. Por otra parte, las prácticas de labranza conservacionista o sin labranza -como sería el caso de la soja o la pastura-generan un mejor acceso a sustratos y nutrientes, en particular en la capa superior del suelo, así como condiciones microclimáticas más favorables que, además, pueden beneficiar el crecimiento de hongos en el suelo (Sae-Tun et al. 2022). ...
Este trabajo evalúa la comunidad de nematodos de suelo en ambientes agrícolas y ganaderos con diferente intensidad de uso del suelo en el sudeste de la provincia de Buenos Aires. Se extrajeron nematodos de sitios con diferente intensidad de uso de la tierra: maíz (2 años consecutivos de labranza convencional [LC]), papa (1 año de LC), soja (siembra directa) y pasturas (con animales en pastoreo). Se identificaron 44 géneros de nematodos pertenecientes a 5 grupos tróficos. Los géneros más abundantes fueron Helicotylenchus, Pratylenchus y Cruznema. Se encontraron diferencias significativas en la estructura de la comunidad de nematodos entre los usos de suelo. La abundancia total y por grupos tróficos fue mayor en soja y pastura. Además, en relación con la composición de la comunidad de nematodos de vida libre (bacteriófagos, frugívoros, omnívoros y depredadores), los sitios con maíz y soja presentaron una mayor proporción de fungívoros, mientras que los sitios con papa y pastura mostraron una mayor proporción de bacteriófagos. En relación con los nematodos fitófagos, la comunidad asociada a sitios con mayor disturbio agrícola (maíz y papa) presentó un ensamble diferente y menos diverso que aquellas asociadas a sitios con menor disturbio (soja y pastura). Los índices nematológicos evidenciaron que las dinámicas sucesionales de las comunidades de nematodos se vieron afectadas debido a las prácticas de los usos de suelos. Esto se confirmó a través del análisis del perfil faunal, la mayoría de las cadenas tróficas, sin importar el tipo de uso del suelo, se vieron afectadas por las prácticas agronómicas mostrando redes tróficas maduras. Este trabajo constituye el primer reporte de la composición de las comunidades de nematodos de suelo en campos de producción agrícola y ganaderos del sudeste bonaerense, y contribuye a conocer la ecología de comunidades de los nematodos de suelo impactados por diferentes prácticas antropogénicas.
... These alterations, in turn, affect soil microbial activity and microbial abundance (Venter et al. 2016;Badagliacca et al. 2021). Legumes have been found to enhance microbial activity and soil enzyme content (Helgason et al. 2009;Thapa et al. 2021). ...
Soil and crop management influence soil organic carbon (SOC), chemical composition, and overall soil quality. In a Mediterranean region, a study initiated in 1994 examined the long-term effects of conventional tillage (CT) versus no-tillage (NT) practices. Initially focusing on continuous durum wheat cultivation until 2009, the experiment later introduced a 2-year rotation of durum wheat and Vicia faba L. cover crops in half of the CT and NT fields. SOC was monitored from 2008 to 2018, while microbial biomass (as dsDNA), soluble nitrogen (N), and enzyme activities (EAs) were monitored from 2011 to 2014 to evaluate the rotation’s impact. Between 2009 and 2018, CT yields were on average 15% higher than NT, especially during high rainfall years. NT significantly increased SOC content in the 0–30 cm soil layer, along with higher levels of soluble N, dsDNA, and EAs at 0–10 cm depth. NT led to a 23% and 10% increase in SOC stock and SOC stock per equivalent soil mass compared to CT. EAs increased by over 50% under NT, indicating enhanced biological activity. The SOC increase due to NT was limited to the top 10 cm, with a decrease at deeper depths (up to 50 cm). Introducing cover crops over 4 years did not yield significant impacts, suggesting the need for a longer period to observe noticeable effects. Overall, adopting NT practices resulted in higher SOC concentration, enhanced soil biological activity, and improved biogeochemical cycles, emphasizing the positive impact of NT on soil health and sustainability.
... Microbial communities can be directly affected by tillage through disruption of the soil system [15]. Helgason [16] reported higher bacterial and fungal species diversity in reduced tillage systems compared to conventional tillage. However, arbuscular mycorrhizal fungi (AMF) are generally more abundant in conservation tillage soils [17]. ...
The effects of intensive and reduced tillage, fertilization, and irrigation on soil chemical and microbiological parameters were studied in a long-term field experiment in Hungary. The treatments were plowing tillage, ripper tillage, strip tillage; control (without fertilization), NPK fertilization (N: 160 kg/ha; P: 26 kg/ha; K: 74 kg/ha); and non-irrigation and irrigation. Soil samples were collected through maize monoculture in the fall of 2021 in the 30th year of the experiment. The soil organic carbon, total nitrogen, soil microbial biomass (based on PLFA analysis), and soil enzyme activity were observed to be significantly high in the strip tillage plots, but were lower in the ripper tillage plots, and even lower in the plowing tillage plots. The fungal, arbuscular mycorrhiza fungal, and bacterial biomasses were significantly higher in the strip tillage and ripper tillage plots compared to the plowing tillage plots. The strip tillage treatment was found to be the most favorable cultivation method for improving the microbial biomass and activity of Chernozem soil, followed by the ripper tillage and plowing tillage treatments. The long-term use of chemical fertilizers greatly reduced the soil microbial biomass and negatively impacted the soil microbial community, leading to a decrease in fungi and Gram-negative bacteria. The ratio of cyclopropyl PLFA precursors to cyclopropyl PLFAs, as a “stress factor”, indicated the most stressful bacterial environment was that found in the fertilized, non-irrigated plowed soil.
... It has been found that there is considerable spatial heterogeneity in soil potential functions when all straw is returned to the field . The surface placement of a large amount of straw reduces the contact between straw and soil particles, thereby reducing the sensitivity of microorganisms to microbial decomposition (Helgason et al., 2009). Additionally, core microorganisms are essential components of holobionts and play important roles in various evolutionary processes, such as enrichment, selection, and inheritance (Lemanceau et al., 2017). ...
P. frumentum biomass could be improved by appropriating returning measures.
P. frumentum biomass was excellent in 75% alfalfa returning amount.
Key species of bacteria differed among the alfalfa returning amounts
The relationship of core bacteria and their potential ecological functions are more close to biomass.
The use of green manure returning to field is a common practice in conservation tillage. However, there is limited research on how different amounts of alfalfa can affect saline-alkali soil properties, bacterial community characteristics, and subsequent productivity. In this study, five different amounts of alfalfa return were investigated to understand the biological relationships between rhizospheres soil properties, bacterial communities, potential functions, and the Purus frumentum biomass. The results showed that the biomass was highest when 75% of the alfalfa was returned to the field. This particular amount was associated with relatively low soil pH and electrical conductivity. Additionally, it increased the relative abundance of beneficial bacterial taxa in both core and non-core bacteria. Statistical analysis revealed significant differences in both core (RANOSIM = 0.871, P = 0.001) and non-core (RANOSIM = 0.947, P = 0.001) bacterial communities among the different amounts of alfalfa return based on non-metric multidimensional scaling analysis. Core bacterial taxa and their potential ecological functions were more closely related to plant biomass compared to non-core bacteria based on correlation analysis and multiple regression analysis. Therefore, our results indicate that optimizing the amount of alfalfa return can improve subsequent plant biomass. Regulating soil physicochemical properties and influencing core microbial community structure are of great significance for soil functional stability and crop productivity sustainability.
... Mycotoxins development and production are highly dependent on environmental factors such as temperature, moisture content, humidity and pre-and post-harvest cultural practices (Milani, 2013;Nyangi et al., 2016;Sasamalo et al., 2018). Another common pre-harvest practice influencing mycotoxin contamination is the tillage method; it has been reported from several studies that the tillage method is one of the major management practices affecting soil physical parameters (Helgason et al., 2009;Janusauskaite et al., 2013) as A. flavus and Fusarium inoculum sits on soil surface and jumps up to maize ears due to rain splash or wind, tillage will submerge this fungi/mould population and prevent them from contaminating grains or pods as cannot reach soil surface. This is because the quality of the soil highly depends on several factors, such as soil structure, natural productivity and human influence. ...
This study assessed the knowledge, attitude, and practices (KAP) of the population in three districts in Tanzania on issues related to mycotoxin contamination and exposure. The study employed a cross-sectional design. Data were collected using a questionnaire survey, which was administered to gather quantitative data in 180 randomly selected households in three districts of Tanzania. In addition, qualitative data were collected using key informant interviews (KIIs) of 12 purposively selected respondents and 6 focus group discussions (FGDs) of six to twelve participants. Quantitative data were analysed in SPSS version 20 for Windows 180 using descriptive statistics and a chi-square test. While the qualitative data were analysed in ATLAS.ti 8 for Windows. A majority of respondents (25.1%) had never heard of mycotoxins, 20.1% were not aware of how mycotoxins are acquired, and none (0%) of the respondents claimed to never become sick after eating moulded/contaminated crops. The majority, 14.5% and 2.8% of the respondents, were not aware of prevention measures for animals and humans from mycotoxins, respectively. Only 8.9% agree that they are at risk of getting mycotoxins, 14% agree that it is safe to eat contaminated food, and 52.5% do not discard the mycotoxins contaminated food. The majority, 81.6%, dry their crops on top of the floor or bare grounds, almost 42.5% do not sort their crops before storage, and 28.5% agree to consume the defective/sorted crops. Therefore, it is recommended that health education interventions to create awareness among the public should be a priority and should be integrated into the existing control strategies
... The microbial abundance (total PLFA) of the consolidation wetland was overall lower than observed in other wetland research and we hypothesize this is associated with low soil moisture conditions as the study took place during a period of drought (Balasooriya et al., 2008;Konschuh, 2013). Fungal PLFA abundance was correlated with community structure in surface soils which is typical for this region (Figure 7) (Helgason et al., 2009). We observed that the fungal PLFA abundance associated with chemical functional groups that represented four protected forms of organic matter, specifically 1,637, 1,418, 1,504, as well as 1,040 (Figure 8). ...
Drainage leads to trade-offs between crop production efficiency and wetland conservation, with complex impacts on ecosystem services. In North America’s Prairie Pothole Region, wetland drainage is widespread, often to increase the available land for cultivation, prevent crop loss due to flooding, and manage soil salinity. Wetlands are known for providing key ecosystem services such as improved water quality, flood mitigation, and carbon storage. There is limited research on how changes to soil hydrology and soil redistribution through wetland drainage can impact soil carbon storage and persistence in this region. This research evaluates factors that contribute to soil carbon storage in drained prairie pothole wetland based on 33 drained wetlands in Saskatchewan, Canada. These analyses showed regional differences in the response of soil carbon storage to drainage that are driven by environmental factors such as annual precipitation, temperature, and wetland permanence. We observed increasing soil carbon storage from the Dark Brown to Black soil zones, as well as with longer wetland pond permanence. The sampling depth used for calculating soil carbon storage was especially important when comparing geographically across the soil zones as the Black soil zone had greater soil carbon stored at depth. Soil carbon was also intensively monitored over 2 years following installation of surface drainage across a wetland complex (8 drained wetlands) where water was partially directed to a consolidation wetland. We further assessed changes in soil carbon dynamics and protection from microbial decomposition based on three soil organic matter fractions, ATR-FTIR for organic matter functional groups, and phospholipid fatty acid analysis to understand the microbial community abundance and structure. After 2 years following drainage, ephemeral wetlands with short pond permanence were found to be most sensitive to drainage and the only wetland class with decreases in soil carbon. The temporary and seasonal wetland classes showed no significant differences in soil carbon content but there were changes in the organic matter with depth due to soil redistribution during drainage implementation. Jointly, this research provides region-specific estimates of soil carbon storage in drained prairie pothole wetlands that can be used to inform wetland soil carbon management in cultivated fields.
... Previous studies have shown that NT with crop residue improved SOC in different aggregate size fractions (Chellappa et al., 2021;Sekaran et al., 2021;Tian et al., 2014;Zheng et al., 2018). Thus, altered soil physical and chemical properties under tillage activities create significantly different habitats for microorganisms and result in shifts of microbial community structure (Helgason et al., 2009;Mathew et al., 2012). Soil biochemical properties are considered sensitive to changes in the management systems, therefore, can be used to detect variations due to different management practices (van Es & Karlen, 2019). ...
Using manure appropriately may enhance organic carbon and hydro‐physical properties while avoiding the negative impact on the environment. However, how manure impacts soils, especially at lower depths, is still not well studied. Therefore, the objective of this study was to assess the impact of different manure and inorganic fertilizer application rates on soil profile organic carbon and hydro‐physical properties under corn (Zea mays L.)–soybean (Glycine max L.)–spring wheat (Triticum aestivum L.) rotation at Beresford (established in 2003) and Brookings (established in 2008) sites in South Dakota. The treatments included low manure (LM), medium manure (MM), high manure (HM), medium fertilizer (MF), high fertilizer (HF), and control (CK). Four replicated intact soil cores were collected from all the treatments at 0‐ to 10‐cm, 10‐ to 20‐cm, 20‐ to 30‐cm, and 30‐ to 40‐cm depths. Considering treatments by depth interactions, the LM and MM decreased bulk density (ρb) by 6.9%–22.1%, as compared to the CK at 0–30 cm for either site. The HM decreased ρb by 16.4%–24.7%, as compared to the HF at 30–40 cm for either site. On observing treatment as the main effect, the MM and HM increased the soil water retention (SWR) at 0 and −5 kPa compared to MF, HF, and CK in Brookings, and the MM increased the SWR at −30 kPa as compared to the MF in Beresford at 0‐ to 40‐cm depths. The data suggest that continuous manure application may enhance organic carbon and hydro‐physical properties at lower depths. Therefore, this study concluded that long‐term manure application showed greater improvements when compared to long‐term application of inorganic fertilizer alone. It can improve hydro‐physical properties, thereby stabilizing the soil structure and improving water retention at lower depths.
... Concurrently CTW without residue (residue removal or burning) showed lower soil microbial count, diazotrophic count, and actinomycetes count compared to ZTW with partial or full residue retention. Immediately after burning of rice straw, top soil layer (0-3 cm) temperature is increased to 50-70 °C which affect drop down of heterotrophic microorganisms population from 77 to 9% 49 . Conventional tilled rice-wheat cropping without residue had the lowest microbial population 38 . ...
In the Indo-Gangetic Plains (IGP), rice-wheat cropping system (RWCS) predominates, producing large quantity of crop residue and its management is major concern. Farmers usually burn the residue to clear the field for succeding crop, and burning damages soil microbes, resulted in loss of soil organic matter. Hence, current study was conducted to assess the impact of different Happy seeder based residue management options on changes in microbial dynamics, enzyme activities and soil organic matter content and also to know that alternative method for attaining sustainable wheat productivity in sandy loam soils of Haryana, India. Results revealed that Zero tillage wheat (ZTW) with partial and full residue retention treatments sown with Happy seeder (after using chopper and spreader), and ZTW with anchored stubbles significantly enhanced soil microbial count by 47.9-60.4%, diazotropic count by 59.0-73.1% and actinomycetes count by 47.3-55.2%, grain yield by 9.8-11.3% and biomass yield by 7.4-9.6% over conventional tilled (CT) residue burning and residue removal plots. ZTW sown with surface retention of rice crop residue increased the organic carbon by 0.36-0.42% and the soil moisture content by 13.4-23.6% over CTW without residue load. Similarly, ZTW sown with Happy seeder with full residue enhanced alkaline phosphatase activity from 95.3 µg TPF g −1 soil 24 h −1 in 2018-2019 to 98.6 µg TPF g −1 soil 24 h −1 in 2019-2020 over control plots. Likely, microbial population and enzymatic activity showed strong positive correlation under variable residue retention practices. However, increased microbial population reduced the soil pH from 7.49 to 7.27 under ZTW with residue retention plots. The wheat yield enhanced by 9.8-11.3% during 2018-2019 and 2019-2020 under ZTW with Happy seeder with full residue load over residue burning and residue removal plots. ZTW sown with Happy seeder under full residue retention, achieved maximum net return 43.16-57.08 × 10 3 ₹ ha −1) and B-C ratio (1.52 to 1.70) over CTW without residue. Therefore, rice residue needs to be managed by planting wheat using appropriate machinery under ZT for sustaining higher productivity in RWCS and improve soil health and environment under IGP regions. The primary cropping system in the northwestern (N-W) Indo-Gangetic Plains (IGP) of India is the rice-wheat cropping system (RWCS), which covers 4.1 million hectares, primarily in the states of Punjab, Haryana, Utta-rakhand, and western Uttar Pradesh and produces 34 million tonnes of rice crop residue 1. According to recent estimates, Southeast Asian countries produce 150 MT of rice residues each year 2,3. Harvesting and threshing of coarse rice are largely and commonly done by combine harvesters ending into leftover residues behind (in narrow strips or gluts), particularly when these machines are not attached with spreader. The window for disposal or use of rice residues is very constrained between rice harvest and the sowing of rabi (october to november) OPEN
... However, if the fungal population is submerged due to deep tillage, it will not be able to contaminate crops since it cannot reach the soil surface [48]. Furthermore, Helgason et al. [49] have argued that no tillage practices can result in increased bacterial and fungal biomass at the soil surface which may imply that there would be a higher likelihood of fungal growth and mycotoxins production in a farm practicing shallow tillage or under no tillage than in cases of a farm implementing deep tillage. However, our results could have been infuenced by other postharvest handling practices since the maize samples obtained from households had been subjected to other postharvest management practices including methods of maize drying, storage, and shelling, and therefore, the efects of land tillage methods would be masked by afatoxin contamination from these postharvest practices. ...
Aflatoxin contamination of maize is a threat to food security and public health for households that depend on farming in developing countries. The objective of this study was to determine levels of total aflatoxins in maize from farms adopting different artisanal aflatoxin control methods. A cross-sectional study was conducted with 315 maize farmers who provided maize samples for aflatoxin analysis and additional data on artisanal aflatoxin control methods applied at farm level. Maize grains were ground, and levels of aflatoxins were determined using competitive enzyme-linked immunosorbent assay. Data were analyzed by computing descriptive statistical measures, and binary logistic regression was used to determine the relationship between levels of aflatoxin in maize and artisanal control methods applied in different farms. Aflatoxin was detected in 98% of maize samples with a mean total aflatoxin level of 12.86 μg/kg which was above the maximum tolerable limits. There was a significant difference in total aflatoxin levels in maize obtained from farms which practiced minimum tillage compared to those practicing deep tillage ( p = 0.015). Drying maize on bare ground had a higher likelihood of aflatoxin contamination than drying maize on tarpaulin ( p = 0.005). One-third of maize samples had aflatoxin levels exceeding the set maximum limit, with maize samples from lowland areas having high proportions of aflatoxin-positive cases as compared to uplands. Artisanal aflatoxin control technologies such as land tillage, types of platforms for drying maize, and sources of maize seed significantly influence the level of aflatoxins in maize samples. We recommend targeted active surveillance for aflatoxins, continuous public education, and adoption of farm-level mitigation measures to reduce the impact of aflatoxin contamination in farming communities.
... The AMF abundance was often correlated with the mass of macro aggregates which physically protect soil organic carbon (Six et al., 2006). Simmons and Coleman, 2008;Helgason et al., 2009.It was reported that tillage could significantly decrease soil fungi by physically disrupting their hyphal networks and/or by affecting soil moisture regime, resulting in a decreased fungal biomass. The abundance of fungi especially AMF increased significantly in ZT, which was in agreement with previous studies (Spedding et al., 2004;Alguacil et al., 2008). ...
Energy usage is exactly proportional to population growth in the current
environment. As a result, demand for power rises in tandem with population
growth. However, daily and seasonal variations in electricity demand exist.
So, we’ll talk about energy storage systems for balancing generation and
demand in this article.
Because of growing concerns about rising energy prices, most renewable
energy sources are being combined into the power grid as distributed energy
resources (DER). This increase in DER penetration raises concerns about load
stability and matching and reliability and power quality. The electric grid must
be able to encounter customer demand. The energy storage system (ESS) can
boost efficiency and reliability while also giving the PV system more power
control options.
... No-tillage is an alternative to conventional tillage, and it usually increases the aggregation of soil organic matter (SOM) and soil biota (Six et al., 2000) and reduces soil erosion and production expenses by saving fuel, equipment, and labor (Uri, 1999;Huang et al., 2013). Soil microbial communities are more abundant in no-tillage soil than in conventional tillage (Govaerts et al., 2007;Helgason et al., 2009). Many Chinese farmers still use traditional tillage methods, especially in the Huang-Huai-Hai Plain in China, including deep plowing and rotational tillage (Chen et al., 2017). ...
Introduction
Conservation tillage is a widely used technique worldwide, but the effects of conservation tillage on bacterial community structure are poorly understood. We explored proportional alterations in the bacterial community under different tillage treatments.
Methodology
Hence, this study utilized high-throughput sequencing technique to investigate the structure and assembly processes of microbial communities in different tillage treatments.
Results and discussion
Tillage treatments included tillage no-straw retention (CntWt), no-tillage with straw retention (CntWntS), tillage with straw retention (CntWtS), no-tillage and no-straw retention (CntWnt). The influence of tillage practices on soil bacterial communities was investigated using Illumina MiSeq sequencing. Different tillage methods and straw retention systems significantly influenced soil parameters such as total potassium and pH were not affected by tillage practices, while straw retention significantly affected soil parameters including nitrogen content, available phosphorus and available potassium. Straw retention decreased bacterial diversity while increased bacterial richness. The effect of straw retention and tillage on bacterial communities was greater than with no tillage. Phylogenetic β-diversity analysis showed that deterministic homogeneous selection processes were dominated, while stochastic processes were more pronounced in tillage without straw retention. Ecological network analysis showed that microbial community correlation was increased in CntWntS and CntWnt. Straw retention treatment significantly increased the relative abundance of bacterial taxa Proteobacteria, Bacteroidetes, and OD1, while Nitrospirae, Actinobacteria, and Verrucomicrobia significantly decreased.
Conclusion
The conservation tillage practices significantly affect soil properties, bacterial composition, and assembly processes; however, further studies are required to investigate the impact of different crops, tillage practices and physiological characteristics on bacterial community structure and functions.
... In addition, high SOC content provides more favorable environmental conditions for the microbial communities by improvement of soil aggregation, moisture, and proper soil temperature which can lead to an increase in microbial abundance (Helgason, Walley, & Germida, 2009;X. Zhang et al., 2018). ...
Today, the resources required for agricultural production in the world
are not unlimited and a continuous development cannot be achieved to
the desired extent by disrupting the natural balance. Sustainable
agriculture is of utmost importance in terms of creating a society that
meets its needs without endangering future generations. It is necessary
to increase the productivity of our agricultural lands by protecting soil
and water resources, protecting natural resources, combating erosion
and forest fires, ensuring biodiversity, integrated pesticide
management, and using appropriate cultivation techniques in
agriculture. Organic agriculture, which has become more and more
important in recent years, will always be an important requirement for
sustainable living and sustainable agriculture.
For a sustainable agriculture, macro and micro nutrients have an
important role for both the soil and the plant, in case of excessive or
underuse, some adverse events occur in the soil and the plant, and accordingly, it causes great losses in terms of yield. Again, in terms of
the sustainability of the cotton plant, macro and micro nutrients have
important effects, and in case of deficiency and excess, it can cause
significant problems in the plant.
... The microbial community's composition was determined by performing a PLFA analysis with group-specific fatty acid methyl esters in accordance with a modified procedure of White et al. (1979), which was derived from the original technique of Bligh and Dyer (1959), as stated in Helgason et al. (2009). Fungal and bacterial biomass in different treatments was assessed using the fungal biomarker 18:2ω6,9 and the 13 bacterial biomarkers (i14:0, i15:0, a15:0, i16:0, 16:1ω7c, 10Me16:0, i17:0, a17:0, cy17:0, 10Me17:0, 18:1ω7, 10Me18:0, and cy19:0) (Bååth and Anderson 2003). ...
Diversification of conventional cereal-based cropping systems with pulse crops may aid producers to grow crops in an appropriate sequence and frequency with environmental, social, and economic benefits. This study examined the effects of including three pulse crops with different rooting depths (shallow- and deep-rooted) in wheat-based crop rotations on soil aggregate size distribution under semi-arid and rain-fed conditions. A 4 year cycle rotational study was established in Brooks, AB, using five selected treatments: continuous wheat, wheat alternately grown with lentil, field pea, or chickpea, or lentil and chickpea alternately grown with wheat. Soils were collected from 0–5 cm depth and dry-sieved to produce eight aggregate size classes, <0.053, 0.053–0.125, 0.125–0.149, 0.149–0.05, 0.05–1.0, 1.0–2.0, 2.0–6.35, and >6.35 mm. The continuous wheat treatment improved the macro-aggregates (>6.35 mm) development, whereas the rotations with pulse–wheat crops increased the micro- and meso-aggregates (0.50–1.0 and 0.15–0.5 mm) development. Soils sampled at 0–15 cm depth were used for soil organic matter and microbial analysis. The pulse–wheat rotations collectively had more light fraction organic matter (LFOM) than the continuous wheat, and chickpea alternated with wheat had the highest amount of LFOM in both years. All treatments had similar soil microbial biomass and microbial community composition. Our study underscores the contribution of pulse crops in cereal-based cropping systems in the formation of small aggregates.
... Previous studies have shown that NT with crop residue improved SOC in different aggregate size fractions (Chellappa et al., 2021;Sekaran et al., 2021;Tian et al., 2014;Zheng et al., 2018). Thus, altered soil physical and chemical properties under tillage activities create significantly different habitats for microorganisms and result in shifts of microbial community structure (Helgason et al., 2009;Mathew et al., 2012). Soil biochemical properties are considered sensitive to changes in the management systems, therefore, can be used to detect variations due to different management practices (van Es & Karlen, 2019). ...
Agricultural management practices tend to influence soil structure stabilization, mediating many physical, chemical, and biological processes in soils. Therefore, understanding the long‐term effects of management practices on various soil health indicators is crucial to develop sustainable agricultural practices. This study aimed to assess the long‐term conventional and conservation tillage effects on soil physical (aggregates) and biochemical (soil organic carbon [SOC], enzymes, and microbial biomass) parameters under a range of tillage practices in a corn–soybean rotation in Nebraska. The experiment was conducted at two locations as follows: (1) Concord site (36 years) with the three treatments: no‐till (NT), disk, and moldboard plow; and (2) Lincoln site (40 years) with four tillage treatments: NT, double disk, chisel, and moldboard plow. Results showed that NT at both sites significantly increased SOC concentration by 24%–66% compared to moldboard plow. Similarly, double disk tillage increased SOC by 54% compared to the moldboard plow at the Lincoln site. Arylsulfatase, β‐glucosidase, hot‐ and cold‐water extractable carbon, microbial biomass carbon, and nitrogen concentrations significantly decreased with the increased tillage intensity at both sites. This implies that the NT increased these parameters compared to the disk and moldboard plow. However, aggregate size fraction 0.053–0.25 mm was the only parameter higher under moldboard plow (20.8%) than NT. Overall, the results from these long‐term studies indicate that NT, and to a lesser extent the reduced tillage practice of disk till, can improve soil health more than conventional tillage practices under a corn–soybean cropping system, suggesting the adoption of sustainable agricultural practices to improve soil health.
... The crushed leaves were digested using the H 2 SO 4 -H 2 O 2 digestion method. After that, the Kjeldahl method, vanadium molybdenum yellow colorimetry, and flame photometry were used to measure the N, P, and K of the leaves [43,44]. ...
Tea plants are widely planted in tropical and subtropical regions globally, especially in southern China. The high leaching and strong soil acidity in these areas, in addition to human factors (e.g., tea picking and inappropriate fertilization methods) aggravate the lack of nutrients in tea garden soil. Therefore, improving degraded tea-growing soil is urgently required. Although the influence of biological factors (e.g., tea plant variety) on soil nutrients has been explored in the existing literature, there are few studies on the inhibition of soil nutrient degradation using different tea plant varieties. In this study, two tea plant varieties with different nutrient efficiencies (high-nutrient-efficiency variety: Longjing43 (LJ43); low-nutrient-efficiency variety: Liyou002 (LY002)) were studied. Under a one-side fertilization mode of two rows and two plants, the tea plant growth status, soil pH, and available nutrients in the soil profiles were analyzed, aiming to reveal the improvement of degraded soil using different tea varieties. The results showed that (1) differences in the phenotypic features of growth (such as dry tea yield, chlorophyll, leaf nitrogen (N), phosphorus (P), and potassium (K) content) between the fertilization belts in LJ43 (LJ43-near and LJ43-far) were lower than those in LY002. (2) RDA results showed that the crucial soil nutrient factors which determine the features of tea plants included available P, slowly available K, and available K. Moreover, acidification was more serious near the fertilization belt. The pH of the soil near LJ43 was higher than that near LY002, indicating an improvement in soil acidification. (3) Soil nutrient heterogeneity between fertilization belts in LJ43 (LJ43-near and LJ43-far) was lower than in LY002. In conclusion, the long-term one-side fertilization mode of two rows and two plants usually causes spatial heterogeneities in soil nutrients and aggravates soil acidification. However, LJ43 can reduce the nutrient heterogeneities and soil acidification, which is probably due to the preferential development of secondary roots. These results are helpful in understanding the influence of tea plant variety on improving soil nutrients and provide a relevant scientific reference for breeding high-quality tea varieties, improving the state of degraded soil and maintaining soil health.
... In the present study, SOC was highly correlated with total PLFA, fungal PLFA, F/B ratio and negatively correlated with bacterial PLFAs. Nevertheless, negative correlation between SOC and bacterial PLFAs has also been observed by Zornoza et al. (2009), Helgason et al. (2009) and Lauber et al. (2008 in corn agricultural fields. ...
In rice–wheat agro-ecosystems, crop residue burning and intensive tillage practices are conventional methods of agriculture in India which deteriorates soil and environmental quality. Present study investigated the individual impact of crop residue burning and excessive tillage as well as combined impact of both practices on soil biological parameters such as organic carbon (SOC), microbial biomass carbon (MBC), soil respiration rate, Bradford reactive soil protein (BRSP), nitrogen mineralization rate and microbial community structure at two soil depths 0–15 and 15–30 cm. Four different burning-tillage combination treatments: no-burn-no-tillage (NBNT); no-burn + tillage (NB + T); after-burn-no-tillage (ABNT) and after-burn + tillage (AB + T) were studied. The microbial community structure was investigated by phospholipids fatty acid analysis (PLFA). Results indicated that crop residue burning and tillage pose significant impact on soil biological parameters and soil microbial community especially at surface soil (0–15 cm). ABNT treatment posed a profound reduction in MBC and soil respiration rate by 54% and 34%, with respect to NBNT. Likewise, a reduction in BRSP content and SOC by 14% and 4% was noticed, while nitrogen mineralization rate enhanced by 19% in ABNT treatment. NB + T treatment significantly (P ≤ 0.05) reduced nitrogen mineralization rate, MBC and BRSP content by 58%, 48% and 25% respectively with respect to NBNT. AB + T treatment remarkably reduced MBC, SOC and BRSP content by 38%, 31% and 23% with respect to NBNT. Principal component analysis indicated that stubble burning and tillage induced a variation in soil microbial communities by ~ 61% and 23%, respectively. From our results, it can be inferred that, no burn and no tillage is the ecologically sustainable agricultural practice for maintaining the soil biological characteristics of the rice–wheat agro-ecosystems of India.
... Plassart et al. (2008) found that agricultural management practices affect fungi to a greater extent than bacteria. Soil fungal communities are highly sensitive to disturbances caused by tillage (Helgason et al., 2009). Tillage practices more strongly influence soil prokaryotic diversity than fungal communities (Xue et al., 2018). ...
Management practices, such as grazing exclusion and reseeding, have been implemented to mitigate the degradation of grassland. Low grazing intensities and reseeding increase grass production. Nevertheless, few studies have investigated the effects of these measures on the soil microbial community structure and function in the Qinghai Tibetan Plateau (QTP). To reveal the effects of management practices on soil microbes and give a reference to assess and improve ecosystems functions, we here evaluated the impact of various types of grazing (exclusion, seasonal, and traditional), reseeding (annual oat (Avena fatua) grassland (RO) and perennial artificial grassland cultivated >10 y), and integrated restoration (weed control and no-tillage reseeding) measures on soil microbial community structure and function in the QTP. The Shannon-Wiener diversity indices were highest for prokaryotes under RO and for fungi under integrated grassland restoration. Relative Actinobacteria abundance was higher under seasonal grazing than that under integrated grassland restoration. The latter had relatively higher abundances of Betaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria and comparatively lower abundance of Thermoleophilia. There were significantly higher abundances of plant pathogens under seasonal grazing than those under other managements. There were significantly high proportions of pathotrophs and saprotrophs (10.0%) under seasonal and traditional grazing, respectively. The proportion of pathotrophs under integrated restoration (10.0%) was about seven-fold greater than that under grazing exclusion (1.5%). The relative differences among treatments in terms of soil water content, plant biomass, and soil C:N partially explained the differences in their prokaryotic community compositions. Increases in soil organic carbon and C:N may explain the observed changes in the soil fungal communities. The management practices affected soil microorganisms mainly by altering the soil nutrient profile. Grazing attracted specific pathotrophs and saprotrophs while repelling certain plant pathogens. Hence, modulations in soil microbial community structure and function must be considered in the process of planning for the implementation of grassland degradation management measures.
... The reduction in microbial population may be due to the generation of heat due to burning crop residues resulting in higher temperature; this may have deleterious effects on microbial survival. Similar results were recorded by Kumar et al. [16]. Helgason et al. [17] reported that conservation tillage practices increase bacterial and fungal population in the soil. ...
The rice - maize cropping system is one of the predominant cropping systems in Telangana state, which also produces large quantities of residues, whose disposal is a major problem. A large quantity of paddy straw is burnt on the farm to clear the field for succeeding crop. On the farm, a significant amount of paddy straw is burned to prepare the land for a subsequent crop. Burning crop residue damages the air and results in the loss of a significant amount of biomass plant nutrients and the entire amount of carbon. The purpose of the study was to investigate the impact of paddy straw burning on soil biological properties (enzyme activities, microbial population) and to know the amount of green house gas (GHG) emissions released due to burning of residue, under two tillage systems viz., no tillage and conventional tillage. Results indicated that there was a significant decrease in soil microbial population, dehydrogenase activity (41.52% in NT and 40.07% in CT), acid and alkaline phosphatase activity and urease activity in soil due to residue burning. It also indicated that there was a rise in CO2, CH4 and N2O emissions 48 hours after residue burning. It can be concluded that crop residue burning leads to decrease in the enzyme activities and soil microbial population. It also leads to rise in green house gas emissions. The impact of rice straw burning on different microbial genera has to be further studied by researchers.
... Fertilizer inputs, planting diversity, and tillage practices affect soil community structure and function in different ways (Mbuthia et al., 2015;Álvarez-Martín et al., 2016). Soil tillage regulates soil microbial community structure and diversity mainly by affecting soil physicochemical characteristics and microbial habitat (Somova and Pechurkin, 2001;Helgason et al., 2009). Fertilizer regulates soil microbial diversity, activity, quantity, and community structure to alter soil nutrient transformation and ultimately soil nutrient effectiveness Ikoyi et al., 2020). ...
Integrated soil-crop management (ISCM) has been shown as an effective strategy to increase efficiency and yield while its soil microbial community structure and function remain unclear. We evaluated changes in soil physicochemical factors, bacterial community structure responses, and the contributions of soil properties and bacterial communities to summer maize-winter wheat yield and GHG emissions through an ISCM experiment [T1 (local smallholder farmers practice system), T2 (improved management system), T3 (high–yield production system), and T4 (optimized management system)], which could provide scientific guidance for sustainable development of soil in summer maize-winter wheat rotation system. The results showed that the optimized ISCM could improve the soil quality, which significantly changed the soil bacterial community structure to reduce GHG emissions and increase yield. The co-occurrence network density of T3 was increased significantly. The Acidobacteria (class) and OM190 (class) were enriched in T2 and T4. The Frankiales (order) and Gaiellales (order) were enriched in T3. However, the changes in different crop growth stages were different. At the wheat jointing stage and maize mature stage, T4 could enhance carbon-related functional groups, such as aromatic hydrocarbon degradation and hydrocarbon degradation, to increase the soil organic carbon content. And at the maize tasseling stage, T4 could enhance nitrogen-related functional groups. And soil bacteria structure and function indirectly affected annual yield and GHG emission. T2 and T4 exhibited a similar soil microbial community. However, the yield and nitrogen use efficiency of T2 were reduced compared to those of T4. The yield of T3 was the highest, but the GHG emission increased and soil pH and nitrogen use efficiency decreased significantly. Therefore, T4 was a suitable management system to improve soil quality and soil bacterial community structure and function to decrease GHG emissions and increase the yield of the summer maize-winter wheat rotation system.
... In addition, high SOC content provides more favorable environmental conditions for the microbial communities by improvement of soil aggregation, moisture, and proper soil temperature which can lead to an increase in microbial abundance (Helgason, Walley, & Germida, 2009;X. Zhang et al., 2018). ...
... Among various tillage practices, reduced tillage (techniques that minimize soil disturbance and leave crop residues or stubble on the soil surface instead of incorporating them into the soil) and no-till technologies are held to have beneficial effects on soil organic carbon content, nutrient transformation [5,11], and soil microbiome enrichment and activity enhancement [5,13,14]. Strip-till is a tillage protection system that minimizes plowing and I. ...
In several studies, the discriminating factor in land use of arable soil is tilling, along with its depth and intensity. Reduced and no-till technologies are held to be beneficial for soil health. Strip-till reduces soil disruption and enables the application of liquid fertilizer directly in rows at different levels. The objective of the research reported here was to evaluate the effects of digestate application on the biochemical and microbiological properties of soil at various soil depths. Three doses of digestate (0, 20, and 40 m³∙ha⁻¹) applied at three different soil depths (0–10, 10–15, and 15–20 cm) were tested in two seasons (2020 and 2021) of semi-operational field trials with maize cultivated according to strip-till practice. In 2020, a lower (20 m³∙ha⁻¹) dose of digestate caused the most significant improvement in β-glucosidase, urease, and basal and L-alanine-induced respiration in topsoil (0–10 cm) and in oxidizable carbon in mid-soil (10–15 cm). In 2021, the most significant positive effect on arylsulfatase, N-acetyl-β-D-glucosaminidase, urease, and all types of respiration were caused by higher (40 m³∙ha⁻¹) digestate dose in mid-soil (10–15 cm). The benefits of the strip-till amended digestate in 2020, as revealed by respiration indicators, strongly decreased with soil depth. Finally, the markedly positive impacts of the digestate applied via the strip-till agromanagement technique were similar for three different depths of soil in 2021, verifying its benefits.
... Plant-microbiome interactions influence a wide range of biogeochemical processes, including mineralization of organic matter (Fontaine et al., 2007;Hu et al., 2020) and the cycling of biologically critical elements such as potassium, nitrogen and carbon (Mendes et al., 2014). It is well established that the composition and relative abundance of soil microbiomes play essential roles in enhancing soil quality, improving soil ecosystem functions, and maintaining plant health and growth (Helgason et al., 2009;Kong et al., 2011). Soil contains a huge number of beneficial microorganisms that drive plant health and productivity (van der Heijden et al., 2008), and serves as protectants against phytopathogens (Philippot et al., 2013). ...
Continuous cropping obstacles caused by the over-cultivation of a single crop trigger soil degradation, yield reduction and the occurrence of plant disease. However, the relationships among stability, complexity and the assembly process of soil microbial community with continuous cropping obstacles remains unclear. In this study, molecular ecological networks analysis (MENs) and inter-domain ecological networks analysis (IDENs), and a new index named cohesion tools were used to calculate the stability and complexity of soil microbial communities from eight potato cultivars grown under a continuous cropping regime by using the high-throughput sequencing data. The results showed that the stability ( i.e. , robustness index) of the bacterial and fungal communities for cultivar ZS5 was significantly higher, and that the complexity ( i.e. , cohesion values) was also significantly higher in the bacterial, fungal and inter-domain communities ( i.e. , bacterial-fungal community) of cultivar ZS5 than other cultivars. Network analysis also revealed that Actinobacteria and Ascomycota were the dominant phyla within intra-domain networks of continuous cropping potato soil communities, while the phyla Proteobacteria and Ascomycota dominated the correlation of the bacterial-fungal network. Infer community assembly mechanism by phylogenetic-bin-based null model analysis (iCAMP) tools were used to calculate the soil bacterial and fungal communities’ assembly processes of the eight potato cultivars under continuous cropping regime, and the results showed that the bacterial community was mainly dominated by deterministic processes (64.19% - 81.31%) while the fungal community was mainly dominated by stochastic processes (78.28% - 98.99%), indicating that the continuous-cropping regime mainly influenced the potato soil bacterial community assembly process. Moreover, cultivar ZS5 possessed a relatively lower homogeneous selection, and a higher TP, TN, AP and yield than other cultivars. Our results indicated that the soil microbial network stability and complexity, and community assemble might be associated with yield and soil properties, which would be helpful in the study for resistance to potato continuous cropping obstacles.
... One of the reasons for the different turnover rates could be differences in carbon use efficiency in the CA top-layer caused by microbial functional diversity (Domeignoz-Horta et al., 2020;Mangalassery et al., 2015). Changes towards a more fungal dominated microbiome have earlier been reported under no-till management (Frey et al., 1999;Helgason et al., 2009;Sun et al., 2016). Findings from our MSIR incubation support this hypothesis, since C-sources associated to fungal metabolome have separated the CA top-layer from the other soils (Fig. 5). ...
Conservation agriculture (CA) has been reported to affect nutrient cycling. This study aims to investigate how CA induced soil organic matter stratification affects carbon and nitrogen turnover. A case farm study was established on two Danish farms with conventional ploughed tillage (P) and CA practises. Here, we studied how organic matter stratification patterns to 50 cm soil depth differed between the two systems. Further we investigated differences in carbon and nitrogen mineralization patterns in lab incubation experiments. Average stratification ratio, the ratio between soil C and N content in the upper 5 cm and at 20–30 cm, the depth of the plough layer in the ploughed system, was 1.86 and 1.61 under CA and 1.04 and 1.06 under P. Carbon respiration from intact soil core incubation was affected by soil total carbon content, and showed stronger stratification in CA than in P. Nitrogen mineralization rates from intact soil core incubation was largest in CA top-layer compared to CA 13.5–16.5 cm layer and both P soil layers, with initial mineralization followed by immobilization during the second half of the a four-week incubation. Net change in mineral nitrogen after incubation was only apparent in the 13.5–16.5 cm layer in P, with an average N mineralization rate of 0.08 mg N kg⁻¹ soil d⁻¹. Sieving to 2 mm did not affect N mineralization dynamics. Field-based ammonium to nitrate ratio was higher in CA than in P soils, across varying soil depths and time-points over the entire year. Soil acidity was reduced by one pH unit in CA compared to P. Microbial metabolic capacity was significantly larger in the top 5 cm of CA from the deeper depths, and from the P soils. In conclusion, carbon and nitrogen mineralization, as well as microbial metabolic capacity were strongly affected by an increased stratification ratio of organic matter in CA.
... Such inconsistency and lack of response were unexpected given the increased soil C and N in amended soils, properties that are commonly associated with increased microbial biomass (Lehmann et al., 2011;Wang et al., 2016). It is possible that the physical disturbance associated with yearly soil tilling affected the abundance of fungi (Helgason et al., 2009;Mirás-Avalos et al., 2011) and that filamentous bacteria, e.g., Actinobacteria, are less impacted by tillage. Additionally, the recalcitrant quality of biochar was expected to increase GP:GN ratios provided their association with complex or labile organic matter decay (Fanin et al., 2019), but no shifts in their abundance ratios were observed resulting from biochar amendment. ...
Altered precipitation patterns and increased water demands from urban, industrial, and environmental needs often reduce the volume of irrigation water available for agriculture. Strategies that reduce irrigation water inputs, e.g., deficit irrigation (DI), need further evaluation to determine potential impacts on yield and soil microbial communities driving critical soil biogeochemical cycles. Whether soil organic amendments can stabilize DI effects on yield and microbial communities remains unknown. Processing tomato beds were established in a full factorial experimental design of soils unamended or amended with a one-time application—four to five years before sampling—of either biochar or biochar with compost and three irrigation regimes: full (100 % of plant water demand), or DI treatments at 75 % or 50 % of full irrigation. We profiled soil bacterial and archaeal community compositions for two growing seasons and determined soil C and N metabolic potentials and biomass of microbial groups using high throughput sequencing of 16S rRNA genes and phospholipid fatty acid analysis. We tested the discrete and interactive effects of DI and soil amendments on soil chemical and biological properties, and crop yield. DI had stronger effects on the bacterial and archaeal community composition than soil organic amendments. However, 75 % DI did not strongly affect bacterial and archaeal community composition or the total and individual biomass of microbial groups, but it increased irrigation water productivity of processing tomatoes. Although soil amendments did not stabilize the compositional shifts induced by DI, their recalcitrant C still had residual effects on the bacterial and archaeal community composition years after their incorporation. Furthermore, soil moisture correlated with bacterial and archaeal community's C and N metabolic potentials, likely augmenting the amendments' C and N residence time in DI soils. Our results provide insight into water-saving mechanisms that could increase profit margins in water-scarce years without affecting microbial populations that support plant growth and productivity.
... Plassart et al. (2008) found that agricultural management practices affect fungi to a greater extent than bacteria. Soil fungal communities are highly sensitive to disturbances caused by tillage (Helgason et al., 2009). Tillage practices more strongly influence soil prokaryotic diversity than fungal communities (Xue et al., 2018). ...
... In addition, an economic analysis of the first 12 years of the study found that while NT was best for soil conservation, it generally provided the lowest profitability due to inconsistent and significant yield advantage coupled with a higher production cost, which was mainly linked to herbicide cost . Other studies have focused on total and labile organic matter fractions (Liang et al. , 2004, plant diseases (Fernandez et al. 1999), weed communities (Hume et al. 1991), and microbial community composition (Helgason et al. 2009(Helgason et al. , 2010a(Helgason et al. , 2010b. ...
Canada's interest in agricultural lands has changed with time from a desire of crop yields at Confederation through to discussions in the Senate on adaptation and resilience in 2018. Long-term research experiments (LTRs) have been present and utilized by federal and university researchers to provide answers throughout. Here we highlight the importance of LTRs by identifying the historical context of LTRs and soil health research in Canada. We then briefly describe the history and key results from select LTRs and illustrate the wealth of information collected from the North American Project to Evaluate Soil Health Measurements cross-country point-in-time soil sampling from these LTRs. We discuss the LTRs, and the knowledge gained from them, with the hope that by showing the distinctive narratives associated with each of these study sites, researchers will be inspired to use them to address their research questions and make sound predictions to facilitate the adaptation of Canadian agroecosystems to climate challenges. Through identifying the value generated by these unique LTRs, we hope that the importance of these sites will inspire not only their continued maintenance but also the next generation of LTRs.
... In longterm conservation tillage systems, soil organic matter stratification and nutrient distribution differences have also been observed (Lal, 2004). Thus, changes in soil physical and chemical conditions associated with conservation tillage result in significantly different microorganism habitats and shifts in soil microbial community structure (Feng et al., 2003;Helgason et al., 2009) The use of wood ash as soil amendment at 4 tons hac -1 improved the soil properties without any negative effect. NT no till, CP chisel plow, MP mouldboard plow, DP deep tillage, MT minimum tillage, RT ridge tillage, CT conservation tillage, WR water retention, BD bulk density, Ksat saturated hydraulic conductivity, TP total porosity, CI cone index, PAW plant available water, -not available. ...
The objective of this paper was to review the various studies of tillage practices effects on some selected soil physical and biological properties from 2000 to 2021 and summarise the findings. The findings of the review indicated that gen-erally, No-tillage (NT) systems has greater benefits than the conventional tillage systems under various soil, environmental, and management conditions. These benefits include using fewer machines, reducing fuel cost, reduced soil loss due to improved aggregate stability, improved soil temperature, and minimal soil erosion due to the protective effect of crop residues left on the soil surface. Fur-thermore, NT soils possess lower soil bulk density (BD), higher porosity, greater infiltration rate and water retention. Even though some studies reported NT to have higher soil BD and cone index and lower moisture content compared to con-ventional tillage, however, the studies show no significant crop yield difference after long years of practise. In addition, the presence of the crop residues on the surface leads to higher microbial biomass, which improves the soil through bur-rowing and creates more soil pores, thereby improving the soil hydraulic conduc-tivity as compared to conventional tillage practices irrespective of the soil type. Conclusively, the NT system improves soil properties in both short- and long-term duration under various soil types as compared to conventional tillage. NT is therefore recommended for soil and water conservation purposes which would lead to higher crop yield.
Crop rotation is a cultural practice in disease management used to break the disease cycle, resulting in a reduction of inoculum. In Ohio, crop rotations have been reduced in diversity, with many farmers shifting to corn-soy rotations from more diverse rotations featuring wheat. We investigated the impact of this shift on soil fungal communities under corn by conducting synthetic long-read amplicon sequencing. DNA was extracted from soil sampled during the corn-growing season at two locations in Ohio with replicated long-term rotation plots in a corn–soybean (CS) and corn–soybean–winter wheat (CSW) rotation in 2018, 2019, and 2020. 18s-ITS amplicons were sequenced using Illumina paired with Loopgenomics technology. PERMANOVA analysis revealed that fungal communities were significantly impacted by location, rotation, and time. Shannon and Simpson diversity indices implied fungal species diversity was significantly higher in the CS rotation. Indicator species analysis revealed 20 species indicative of the CSW rotation, including Mortierella, Hymenoschyphus, Ascobolus, and Saitozyma species, and 36 species indicative of the CS rotation, including Fusarium, Neoaschocyta, Zalerion, and Trichoderma species, among others. Indicator species amplicon sequencing variant reads for the CSW rotation were not correlated with the decline in corn yield or soil nitrogen, carbon, or active carbon. However, they were positively correlated with soil organic matter.
[Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .
Plant–soil feedbacks (PSFs) underlying grassland plant richness and productivity are typically coupled with nutrient availability; however, we lack understanding of how restoration measures to increase plant diversity might affect PSFs. We examined the roles of sward disturbance, seed addition and land‐use intensity (LUI) on PSFs.
We conducted a disturbance and seed addition experiment in 10 grasslands along a LUI gradient and characterized plant biomass and richness, soil microbial biomass, community composition and enzyme activities.
Greater plant biomass at high LUI was related to a decrease in the fungal to bacterial ratios, indicating highly productive grasslands to be dominated by bacteria. Lower enzyme activity per microbial biomass at high plant species richness indicated a slower carbon (C) cycling. The relative abundance of fungal saprotrophs decreased, while pathogens increased with LUI and disturbance. Both fungal guilds were negatively associated with plant richness, indicating the mechanisms underlying PSFs depended on LUI.
We show that LUI and disturbance affect fungal functional composition, which may feedback on plant species richness by impeding the establishment of pathogen‐sensitive species. Therefore, we highlight the need to integrate LUI including its effects on PSFs when planning for practices that aim to optimize plant diversity and productivity.
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Two different agricultural tillage practices were used to study how changes in the structure of the soil-litter system affected litter decomposition rates, microbial community composition, and soil organic matter dynamics. Surface straw placement results in spatial separation of carbon-rich litter (C:N ratio 80:1) and mineralized soil nitrogen. In contrast, when the litter is plowed into the soil, straw carbon and soil nitrogen are in intimate contact. Our field studies in Colorado showed that fungal biomass in surface-straw treatments was 144% of that in the incorporated-straw treatments, probably because fungi, with their extensive hyphal networks, are able to utilize both the surface straw carbon and the available soil nitrogen. Field studies using ^1^4C-labeled wheat straw showed that a greater proportion of added ^1^4C was retained in the surface-straw treatment than in the incorporated-straw treatment. Maximum net N immobilization was higher and litter decomposition was slower in the surface straw than in the incorporated straw placements both with and without experimental nitrogen addition. Slower litter decomposition of the surface litter may contribute to reduced soil organic matter losses. Soil organic matter losses may also be reduced in no-till systems as a result of the increase in the ratio of fungal to bacterial activity because of the greater growth efficiency of fungi and the accumulation of carbon in the less decomposable fungal biomass. The surface placement of straw in no-till agriculture allowed management of microclimate and microbial populations so that losses of soil organic matter and nutrients were minimized.
This paper reviews the current knowledge of microbial processes affecting C sequestration in agroecosystems. The microbial contri- bution to soil C storage is directly related to microbial community dynamics and the balance between formation and degradation of mi- crobial byproducts. Soil microbes also indirectly influence C cycling by improving soil aggregation, which physically protects soil organic matter (SOM). Consequently, the microbial contribution to C seques- tration is governed by the interactions between the amount of micro- bial biomass, microbial community structure, microbial byproducts, and soil properties such as texture, clay mineralogy, pore-size distribu- tion, and aggregate dynamics. The capacity of a soil to protect micro- bial biomass and microbially derived organic matter (MOM) is directly and/or indirectly (i.e., through physical protection by aggregates) related to the reactive properties of clays. However, the stabilization of MOM in the soil is also related to the efficiency with which micro- organisms utilize substrate C and the chemical nature of the by- products they produce. Crop rotations, reduced or no-tillage practices, organic farming, and cover crops increase total microbial biomass and shift the community structure toward a more fungal-dominated com- munity, thereby enhancing the accumulation of MOM. A quantitative and qualitative improvement of SOM is generally observed in agro- ecosystems favoring a fungal-dominated community, but the mecha- nisms leading to this improvement are not completely understood. Gaps within our knowledge on MOM-C dynamics and how they are related to soil properties and agricultural practices are identified.
No‐tillage (NT) practices can improve soil aggregation and change the distribution and retention of soil organic matter (SOM) compared with conventional tillage (CT), but the relationships between aggregates and SOM fractions are poorly known. The effects of long‐term (13‐yr) CT and NT management on water‐stable aggregates (WSA) and aggregate‐associated SOM were investigated on a Hiwassee sandy clay loam (clayey, kaolinitic, thermic Rhodic Kanhapludult). Samples were collected at two depths in replicated CT and NT plots and separated into five aggregate size classes by wet sieving. The stability of intact WSA was measured turbidimetrically. The C and N content of total, particulate (POM), and mineral‐associated organic matter was determined for each size class. Whole‐soil organic C was 18% higher in NT (30.7 Mg C ha ⁻¹ ) than in CT (26.1 Mg C ha ⁻¹ ). In CT, macroaggregates (>250 µm) were fewer and less stable than those of NT. The POM C made up ≈36% of whole soil C regardless of tillage, but the quantity of POM was nearly 20% higher in NT than in CT. The POM comprised a higher percentage of total aggregate N in surface soils of NT than in CT and values increased with increases in aggregate size. In NT, concentrations of total and mineral‐associated C and N were higher in the 106‐ to 250‐µm WSA than in the other size classes but, in CT, the concentrations were similar among size classes. An alternative view of aggregate organization is discussed in which microaggregates are formed in association with POM at the center of macroaggregates, helping to explain relationships between SOM storage and aggregate size distributions under different management practices.
Changes in soil aggregation, carbohydrates, and fungal vs. bacterial biomass were monitored following a shift from fallow (bare soil) to various cropping systems in Québec, Canada. Faba bean (Vicia faba) and wheat (Triticum aestivum) were used as annual cropping systems, while lucerne (Medicago sativa), timothy grass (Phleum pratense), bromegrass (Bromus inermis), and reed canary grass (Phalaris arundinacea) were used as perennial cropping systems. Crops were established in spring 1989, on a silty clay loam (Typic Dystrochrept) and a clay loam (Typic Humaquept). After three growing seasons, the mean-weight diameter of water-stable aggregates (MWD) was higher under reed canary grass (2.26 mm in the clay loam and 2.45 mm in the silty clay loam) and timothy (2.13 and 2.26 mm) than under faba bean (1.92 and 1.89 mm) or wheat (2.06 and 1.57 mm). Intermediate values were found under lucerne and bromegrass. Changes in MWD were not correlated with microbial biomass C. Acid-hydrolysable carbohydrates correlated with MWD in the silty clay loam (r2 = 0.42) but the relationship decreased with higher carbohydrate levels in the clay loam (r2 = 0.05). Close correlations were found between MWD and both fungal glucosamine (r2 = 0.68, soils combined) and bacterial muramic acid (r2 = 0.48). Changes in MWD were mostly reflected in aggregates >2 mm, and the close relationship with fungal glucosamine suggests that fungi played a dominant role in soil macroaggregation. Measurement of muramic acid and glucosamine is proposed as a potential approach to compare bacterial vs. fungal contributions to soil aggregation.
Reducing disturbance by tillage and addition of crop residues affects soil biota and their role in soil C storage. For 1 yr in a field station trial in Davis, CA, these treatments were compared: no-tillage + continuous cropping, no-tillage + fallow, standard tillage + continuous cropping, and standard tillage + fallow. The continuous cropping treatment consisted of tomato (Lycopersicon esculentum Mill.) /sorghum-sudangrass [Sorghum bicolor (L.) Moench]/garbanzo (Cicer arietinum L.)/cowpea cover crop [Vigna unguiculata (L.) Walpers ssp. unguiculata]. The fallow rotation omitted the sorghum-sudangrass and cowpea cover crops. No-tillage + continuous cropping resulted in significant changes in the surface layer (0-5 cm): higher microbial biomass C, more fungi as indicated by ergosterol and phospholipid fatty acid analysis, and higher soil NO(3) in summer, and higher pH, soluble K(+), and Olsen P at the end of the experiment. At lower depths (5-15 and 15-30 cm), few differences were observed. Total soil C (at 0-30 cm) was least with standard tillage + fallow, the typical management practice in the region. The soil food web, as indicated by the nematodes, did not become more complex with no-tillage + continuous cropping, contrary to expectations, possibly because higher trophic level nematodes had been eliminated after decades of cultivation. The bacterial decomposition pathway dominated the surface layer in all treatments, but, with no-tillage, opportunistic (colonizer-persistent Group 1) bacterial feeders greatly decreased with depth. Plant productivity, except for weeds, was reduced by no-tillage, especially in the garbanzo crop. By decreasing disturbance and increasing fungi, no-tillage + continuous cropping appears to have accelerated soil C storage but management alterations are needed to produce higher crop biomass in this Mediterranean-Lype climate.
We examined the effect of reduced tillage on the accumulation of fungal- versus bacterial-derived organic matter within the soil matrix by quantifying the amino sugars glucosamine (Glc), galactosamine (Gal), and muramic acid (MurA) in aggregate-size fractions isolated from no-tillage (NT) and conventional-tillage (CT) soil. Intact soil cores (0- to 5- and 5- to 20-cm depth) were collected from the long-term tillage experiment at Horseshoe Bend in Athens, GA. Four water-stable aggregate-size fractions were isolated: large macroaggregates (>2000 μm), small macroaggregates (250-2000 μm), microaggregates (53-250 μ), and the silt + clay fraction (<53 μm). Small macroaggregates were further separated into coarse particulate organic matter (POM) (>250 μm), microaggregates contained within macroaggregates, and the silt + clay fraction. Amino sugars were extracted from all fractions, purified, and analyzed by gas chromatography. Fungal-derived amino sugar C (FAS-C) comprised 63%, while bacterial-derived amino sugar C (BAS-C) accounted for 37% of the total amino sugar C pool under both tillage treatments. No-tillage soil contained 21% more amino sugar C than the CT soil across the entire plow layer. Both, the percentage of total organic C as FAS-C and BAS-C were significantly higher in the silt + clay fraction of NT versus CT soil. The percentage of total organic C as FAS-C was significantly higher in small macroaggregates of NT versus CT soil due to a preferential accumulation of FAS-C in the microaggregates contained within these macroaggregates. These results indicate that microbial-derived C is stabilized in NT soils, due primarily to a greater fungal-mediated improvement of soil structural stability and concurrent deposition of fungal-derived C in microaggregates contained within macroaggregates.
Winter wheat–fallow (W–F) rotation is the predominant cropping system in the Central Great Plains. However, other cropping systems are being suggested because reduced tillage and fallow can provide more residues that can increase soil organic carbon (SOC) content and other parameters related to soil quality and functioning. This study compared the microbial biomass and community composition and enzyme activities under native pasture and research plots under grass and different crop intensities (CI) established for 15 years in Akron, CO. The soil (Weld loam; fine, smectitic, mesic Aridic Paleustolls) was under alternative CI rotations (100 and 67%) of winter wheat (Triticum aestivum L.) (W), corn (Zea mays L.) (C), proso millet (Panicum miliaceum L.) (M), and fallow (F) under no-tillage (nt) compared to the typical 50% CI rotation (W–F) under either conventional tillage (ct) and nt. Relative to F–Wct, the 100% (C–M–W) and 67% (C–F–W) CI rotations increased soil microbial biomass C (MBC) and N (MBN) but only at the 0–5 cm depth. Native pasture and 15 years of undisturbed grass plots showed higher soil MBC up to 2–5-fold and 1.4–3-fold when compared to the cropping systems at 0–5 cm, respectively. Similar trends were found for MBN and several enzyme activities. Enzyme activities of C (β-glucosaminidase, β-glucosidase, and α-galactosidase) and P cycling (alkaline phosphatase, acid phosphatase and phosphodiesterase) as a group separated the 100 and 67% CI rotations from the 50% CI rotation (W–Fct) at 0–5 and 5–15 cm of soil. Separation in these enzyme activities was observed for rotations sampled under a crop (W–C–F) compared to when sampled under fallow (F–W–C). Principal component analyses (PCA) of fatty acids methyl esters (FAME) suggested a shift in the microbial community structure with greater fungal populations in pasture, grass, and CI rotations of 100 and 67% compared to W–Fct. The sum of fungal indicators (18:2ω6c, 18:3ω6c, 18:1ω9c, 16:1ω5c) was significantly correlated (r > 0.60; P < 0.05) to β-glucosaminidase, β-glucosidase, acid phosphatase and α-galactosidase activities. After 15 years, our results show that the combination of no-tillage and continuous cropping with reduced fallow frequency in two alternative (100 and 67% CI) rotations for the Central Great Plains have had a positive effect on soil quality parameters such as the microbial populations and community composition but only at 0–5 cm depth, and in several enzyme activities at both 0–5 and 5–15 cm.
Traffic-induced soil compaction and tillage systems can impact the productivity and sustainability of agricultural soils. The objective of this study was to assess the response of soil microbial populations to wheel-traffic in two tillage systems on a Norfolk loamy sand (Typic Kandiudults; FAO classification Luxic Ferralsols). Experimental variables were with and without traffic under conventional tillage (disk harrow twice, chisel plow, field cultivator-planter) vs. no tillage employed in a split-plot design with four replications; main plots were traffic and subplots were tillage. Soil samples were collected from 0-2 and 2-4-cm depths, sieved (2 mm), and used to assess soil-water content, microbial biomass nitrogen (N), dehydrogenase, and microbial characterization using phospholipid ester-linked fatty acid (PLFA) analysis. Traffic increased soil-water content, had little affect on microbial biomass N, and increased microbial activity (no-till plots only) likely due to increased amounts of residue. Soil-water content, microbial biomass N, PLFA estimates of microbial biomass, and microbial activity were all consistently higher in no-till compared to conventional tillage plots. Data from this study suggest that conventional tillage results in a lower, more static, possibly more mature community of microbes while the microbial community under no-till appears to be a younger, more viable growing population. Finally, these data suggest that overall soil quality, at least in the surface soil layer, is improved in agricultural systems employing no-till operations.
The filamentous fungi have dynamic and variable hyphal structures within which cytoplasm can be moved, synthesized, and degraded, in response to changes in environmental conditions, resource availability, and resource distribution. Their study has gone through several phases. In the first phase, direct observation was emphasized without undue concern for interior structures or in the presence of cytoplasm. By the mid-1970s, single biochemical proxies (ergosterol, marker fatty acids, chitin derivatives, etc.) were being used increasingly. The use of these surrogate single measurements continues, in spite of their inability to provide information on the physical structure of the filamentous fungi. Molecular approaches also are being used, primarily through the use of bulk nucleic acid extraction and cloning. Because the sources of the nucleic acids used in such studies usually are not known, taxonomic and phylogenetic information derived by this approach cannot be linked to specific fungal structures. Recently, a greater emphasis has been placed on assessing physical aspects of indeterminate fungal growth, involving the assessment of cytoplasm-filled and evacuated (empty) hyphae. Both of these parameters are important for describing filamentous fungal growth and function. The use of phase contrast microscopy and varied general stains, as well as fluorogenic substrates with observation by epifluorescence microscopy, has made it possible to provide estimates of cytoplasm-filled hyphal lengths. Using this approach, it has been possible to evaluate the responses of the indeterminate fungal community to changes in environmental conditions, including soil management. It is now possible to obtain molecular information from individual bacteria and fungal structures (hyphae, spores, fruiting bodies) recovered from environments, making it possible to link individual fungal structures with their taxonomic and phylogenetic information. In addition, this information can be considered in the context of the indeterminate filamentous fungal lifestyle, involving the dynamics of resource allocation to hyphal structural development and synthesis of cytoplasm. Use of this approach should make it possible to gain a greater appreciation of the indeterminate filamentous fungal lifestyle, particularly in the context of microbial ecology.
Lipid decomposition studies in frozen fish have led to the development of a simple and rapid method for the extraction and purification of lipids from biological materials. The entire procedure can be carried out in approximately 10 minutes; it is efficient, reproducible, and free from deleterious manipulations. The wet tissue is homogenized with a mixture of chloroform and methanol in such proportions that a miscible system is formed with the water in the tissue. Dilution with chloroform and water separates the homogenate into two layers, the chloroform layer containing all the lipids and the methanolic layer containing all the non-lipids. A purified lipid extract is obtained merely by isolating the chloroform layer. The method has been applied to fish muscle and may easily be adapted to use with other tissues.
A field study was conducted to determine the effects and interactions of crop sequence, tillage and residue management on labile N pools and their availability because such information is sparse. Experimental treatments were no-till (NT) vs. conventional tillage (CT), and removal vs. retention of straw, imposed on a barley (Hordeum vulgare L.)-canola (Brassica rapa L.)-field pea (Pisum sativum L.) rotation. 15N-labelling was used to quantify N uptake from straw, below-ground N (BGN), and fertilizer N. Straw retention increased soil microbial biomass N (MBN) in 2 of 3 yr at the four-leaf growth stage of barley, consistent with observed decreases in extractable soil inorganic N at seeding. However, crop yield and N uptake at maturity were not different between straw treatments. No tillage increased soil MBN, crop yield and N uptake compared to CT, but had no effect on extractable soil inorganic N. The greater availability of N under NT was probably related to soil moisture conservation. Tillage effects on soil and plant N were mostly independent of straw treatment. Straw and tillage treatments did not influence the uptake of N from its various sources. However, barley following pea (legume/non-legume sequence) derived a greater proportion of its N from BGN (13 to 23% or 9 to 23 kg N ha-1) than canola following barley (non-legumes) (6 to 16% or 3 to 9 kg N ha-1). Fertilizer N constituted 8 to 11% of barley N uptake and 23 to 32% of canola N uptake. Straw N contributed only 1 to 3% of plant N uptake. This study showed the dominant influence of tillage on N availability, and of the preceding crop or cropping sequence on N uptake partitioning among available N sources.
The distribution of NaHCO3-extractable nitrate-N, ammonium-N, phosphorus (P) and potassium (K) with soil depth (0 to 20 cm in 5-cm increments) at Fort Vermilion (58°23'N 116°02'W), Alberta, was described in the 7th and 8th years of conventional and zero tillage following placement of red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues. Soil nitrate-N concentrations under zero tillage were greater than those under conventional tillage in the 0-5 cm soil layer, below which the concentrations were similar. Ammonium-N and K concentrations followed a similar pattern. However, soil P concentrations were usually not different between tillage systems in the 0-5 cm soil layer, but the concentrations decreased more under zero tillage than under conventional tillage at lower depths. A notable exception for soil phosphate was under canola residues, where the concentration was greater under zero tillage than under conventional tillage at all depths. Uptake of N, P or K by a subsequent wheat crop was usually greater (though not always significantly) under zero tillage than under conventional tillage, and there were no interactions between tillage and crop residue. Therefore, differences in nutrient stratification between the two tillage systems did not translate into differences in wheat nutrient uptake.
Field experiments were conducted to correlate decomposition of red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and wheat (Triticum aestivum) residues, and soil organic C (SOC), under zero tillage and conventional tillage, with soil microbial biomass C (MBC), bacterial functional diversity and microbial activity (CO2 evolution). A greenhouse experiment was also conducted to relate crop residue quality to soil microbial characteristics. Zero tillage increased MBC only in the 0- to 5-cm soil layer. Soil MBC decreased more with soil depth than either microbial diversity or total SOC. Legume GM residues induced greater initial CO2 evolution than the other residues. This means that results that do not include the initial flush of microbial activity, e.g., by sampling only in the season(s) following residue placement, probably underestimate gas evolution from legume crop residues. Residue N, P and K contents were positively correlated with microbial functional diversity and activity, which were positively correlated with crop residue decomposition. Therefore, microbial functional diversity and activity were good indicators of microbial decomposition processes. Residue C/N and C/P ratios (i.e., high C content) were posi-tively correlated with MBC, which was positively correlated with SOC. Therefore, soil MBC was a good indicator of soil quality (soil organic matter content).
In arable systems, seasonal fluctuations of microbiological properties can be significant. We hypothesized that adaptation to soil environmental conditions may contribute to the variation observed, and this was examined by characterization of different microbial community attributes under a range of soil conditions. Soil was sampled from no-till and chisel-tilled fields within a long-term experiment in eastern Washington during growth of spring wheat (Triticum aestivum ). The range of soil environmental conditions covered was extended by amendment of crop residues. Soil samples were characterized with respect to biomass N and biomass P, substrate utilization dynamics, phospholipid fatty acid (PLFA) profiles and whole-soil fatty acid (MIDI-FA) profiles, and with respect to soil environmental variables (bulk density, soil organic C [SOC], temperature, moisture, and inorganic N and P). Bacterial and fungal lipid biomarkers were negatively correlated (P < 0.001), confirming that these subsets of fatty acids are associated with contrasting components of the microbial biomass. Biomass N was closely associated with soil conditions, notably N availability. The proportion of substrates used with no apparent lag phase decreased during summer and was negatively correlated with lipid stress indicators. Cyclopropyl fatty acids accounted for more than 60% of the variation in bacterial PLFA. These observations suggest that adaptation to environmental stresses was partly responsible for the microbial dynamics observed. Tillage practice had little effect on the relationships between soil conditions and microbiological properties. The results showed that MIDI-FA included a significant background of nonmicrobial material and was less sensitive to soil environmental conditions than PLFA.
This chapter illustrates detritus-based food webs responding to various disturbance regimes occurring in conventionally tilled (CT) and non-tilled (NT) systems. The detritus food web is based largely in the soil system, and is important in regulating nutrient cycling and energy flow, it is reasonable to expect that this food web may be a viable and meaningful indicator of disturbance exerted by tillage and alternative weed management strategies. The principal differences in disturbance regimes involve cultivation, herbicide application, residue management and manipulation of weed levels, therefore, emphasis is placed on these factors. The chapter also reviews the results of previous studies, determines how different components of the detritus food web respond to the disturbances relative to each other, and examines the consequences of these disturbances for overall food web structure. Furthermore, while disturbances in CT systems may exert predictable negative effects on most groups of soil organisms, the responses of species assemblages are less predictable. Individual taxonomic species are undoubtedly a more sensitive indicator of ecosystem disturbance than are entire functional groups, and is therefore a more appropriate unit for biomonitoring purposes.
The long-term impact of tillage and residue management on soil microorganisms was studied over the growing season in a sandy loam to loamy sand soil of southwestern Quebec, growing maize (Zea mays L.) monoculture. Tillage and residue treatments were first imposed on plots in fall 1991. Treatments consisted of no till, reduced tillage, and conventional tillage with crop residues either removed from (−R) or retained on (+R) experimental plots, laid out in a randomized complete block design. Soil microbial biomass carbon (SMB-C), soil microbial biomass nitrogen (SMB-N) and phospholipid fatty acid (PLFA) contents were measured four times, at two depths (0–10 and 10–20 cm), over the 2001 growing season. Sample times were: May 7 (preplanting), June 25, July 16, and September 29 (prior to corn harvest). The effect of time was of a greater magnitude than those attributed to tillage or residue treatments. While SMB-C showed little seasonal change (160μgCg−1 soil), SMB-N was responsive to post-emergence mineral nitrogen fertilization, and PLFA analysis showed an increase in fungi and total PLFA throughout the season. PLFA profiles showed better distinction between sampling time and depth, than between treatments. The effect of residue was more pronounced than that of tillage, with increased SMB-C and SMB-N (61 and 96%) in +R plots compared to −R plots. This study illustrated that measuring soil quality based on soil microbial components must take into account seasonal changes in soil physical and chemical conditions.
Additions of (15NH4)2SO4 to the soil inorganic nitrogen (N) pool were used to measure rates of N flux from the mineral soil to surface-applied wheat straw decomposing in intact soil cores collected from a no-tillage (NT) field. Half of the soil cores were treated with a fungicide to reduce fungal populations. Fungicide application significantly reduced fungal biomass, decomposition rates, and net N immobilization in surface residues. Net N immobilization over the study period was estimated to be 1.5 and 0.9 g N m−2 for untreated and fungicide-treated residues, respectively. The rate of 15N transfer averaged 13.4 μg 15N g−1 residue d−1 for untreated wheat straw. Fungal inhibition reduced 15N flux by 59–78%, reductions of similar magnitude to those observed for fungal biomass. Nitrogen transfer in sterilized soil cores accounted for only 7.8% of the total upward N transport in control cores, indicating that abiotic processes did not contribute substantially to N flux. We estimate a total annual fungal-mediated N flux of 2.4 g m−2, which is nearly equivalent to the N immobilization potential predicted, based on initial N and lignin content, for the wheat straw used in this study. We conclude that fungal N translocation is a significant mechanism for soil N input and can account for the observed net N immobilized by surface residues decomposing in the field. Both residue quality and N availability appear to be important controls on fungal biomass associated with surface residues and rates of soil-to-residue N translocation.
bial cell-wall constituents) (Kogel-Knabner, 1993; Zech and Kogel-Knabner, 1994). Hence, the composition and Agricultural management practices have been shown to influence activity of the microbial biomass is an important deter- the decomposer community in soils, with no-tillage (NT) systems favoring fungi as compared with conventional tillage (CT) systems. minant in the amount and quality (defined as structural In this study, we examined six North American agroecosystems with composition) of SOM that accumulate in soils (Elliott respect to the effects of NT vs. CT management systems on the accrual and Coleman, 1988). of microbial cell-wall residues in surface soil. We used total amino Agricultural management practices have been shown sugar contents to estimate living and decomposing microbial cell-wall to influence strongly the size and composition of the mass in soil and the contents of glucosamine and muramic acid to microbial community in soil (Beare et al., 1992; Frey et separate fungal and bacterial contributions to microbial-derived soil al., 1999). Beare (1997) showed that litter placement organic matter (SOM). Compared with estimates of glucosamine and exerts a pronounced influence on the composition of muramic acid present in living biomass of fungi and bacteria, total decomposer communities. Conventional tillage (CT) concentrations of these compounds (745-2076 mg glucosamine kg 21
The measurement of lipid phosphate is proposed as an indicator of microbial biomass in marine and estuarine sediments. This relatively simple assay can be performed on fresh, frozen or frozen-lyophilized sediment samples with chloroform methanol extraction and subsequent phosphate determination. The sedimentary lipid phosphate recovery correlates with the extractible ATP and the rate of DNA synthesis. Pulse-chase experiments show active metabolism of the sedimentary phospholipids. The recovery of added 14C-labeled bacterial lipids from sediments is quantitative. Replicate analyses from a single sediment sample gave a standard deviation of 11%. The lipid extract can be fractionated by relatively simple procedures and the plasmalogen, diacyl phospholipid, phosphonolipid and non-hydrolyzable phospholipid content determined. The relative fatty acid composition can be readily determined by gas-liquid chromatography.
The lipid composition can be used to define the microbial community structure. For example, the absence of polyenoic fatty acids indicates minimal contamination with benthic micro-eukaryotes. Therefore the high content of plasmalogen phospholipids in these sediments suggests that the anaerobic prokaryotic Clostridia are found in the aerobic sedimentary horizon. This would require anaerobic microhabitats in the aerated zones.
The effect of a change of tillage and crop residue management practice on the chemical and microbiological properties of a cereal-producing red duplex soil was investigated by superimposing each of three management practices (CC: conventional cultivation, stubble burnt, crop conventionally sown; DD: direct-drilling, stubble retained, no cultivation, crop direct-drilled; SI: stubble incorporated with a single cultivation, crop conventionally sown), for a 3-year period on plots previously managed with each of the same three practices for 14 years. A change from DD to CC or SI practice resulted in a significant decline, in the top 0-5 cm of soil, in organic C, total N, electrical conductivity, NH4-N, NO3-N, soil moisture holding capacity, microbial biomass and CO2 respiration as well as a decline in the microbial quotient (the ratio of microbial biomass C to organic C; P <0.05). In contrast, a change from SI to DD or CC practice or a change from CC to DD or SI practice had only negligible impact on soil chemical properties (P >0.05). However, there was a significant increase in microbial biomass and the microbial quotient in the top 0-5 cm of soil following the change from CC to DD or SI practice and with the change from SI to DD practice (P <0.05). Analysis of ester-linked fatty acid methyl esters (EL-FAMEs) extracted from the 0- to 5-cm and 5- to 10-cm layers of the soils of the various treatments detected changes in the FAME profiles following a change in tillage practice. A change from DD practice to SI or CC practice was associated with a significant decline in the ratio of fungal to bacterial fatty acids in the 0- to 5-cm soil (P <0.05). The results show that a change in tillage practice, particularly the cultivation of a previously minimum-tilled (direct-drilled) soil, will result in significant changes in soil chemical and microbiological properties within a 3-year period. They also show that soil microbiological properties are sensitive indicators of a change in tillage practice.
We have compared the total microbial biomass and the fungal/bacterial ratio estimated using substrate-induced respiration (SIR) in combination with the selective inhibition technique and using the phospholipid fatty acid (PLFA) technique in a pH gradient (3.0–7.2) consisting of 53 mature broad-leaved forest soils. A fungal/bacterial biomass index using the PLFA technique was calculated using the PLFA 18:2ω6,9 as an indicator of fungal biomass and the sum of 13 bacterial specific PLFAs as indicator of the bacterial biomass. Good linear correlation (p<0.001) was found between the total microbial biomass estimated with SIR and total PLFAs (totPLFA), indicating that 1 mg biomass-C was equivalent to 130 nmol totPLFA. Both biomass estimates were positively correlated to soil pH. The fungal/bacterial ratio measured using the selective inhibition technique decreased significantly with increasing pH from about 9 at pH 3 to approximately 2 at pH 7, while the fungal/bacterial biomass index using PLFA measurements tended to increase slightly with increasing soil pH. Good correlation between the soil content of ergosterol and of the PLFA 18:2ω6,9 indicated that the lack of congruency between the two methods in estimating fungal/bacterial ratios was not due to PLFA 18:2ω6,9-related non-fungal structures to any significant degree. Several PLFAs were strongly correlated to soil pH (R2 values >0.8); for example the PLFAs 16:1ω5 and 16:1ω7c increased with increasing soil pH, while i16:0 and cy19:0 decreased. A principal component analysis of the total PLFA pattern gave a first component that was strongly correlated to soil pH (R2=0.85, p<0.001) indicating that the microbial community composition in these beech/beech-oak forest soils was to a large extent determined by soil pH.
Tillage systems affect the soil physical and chemical environment in which soil organisms live, thereby affecting soil organisms. Tillage practices change soil water content, temperature, aeration, and the degree of mixing of crop residues within the soil matrix. These changes in the physical environment and the food supply of the organisms affect different groups of organisms in different ways. One of the challenges of research in soil ecology is to understand the impacts of management on the complex interactions of all organisms at the soil community level. In addition to the response of organisms to soil manipulations, agriculturalists are interested in the actions of soil organisms on the physical and chemical environment in the soil. Soil organisms perform important functions in soil, including structure improvement, nutrient cycling, and organic matter decomposition. This paper discusses the effects of tillage practices on soil organism populations, functions, and interactions. Although there is a wide range of responses among different species, most organism groups have greater abundance or biomass in no-till than in conventional tillage systems. Larger organisms in general appear to be more sensitive to tillage operations than smaller organisms, due to the physical disruption of the soil, burial of crop residue, and the change in soil water and temperature resulting from residue incorporation. Variations in responses found in different studies reflect different magnitudes of tillage disruption and residue burial, timing of the tillage operations, timing of the measurements, and different soil, crop, and climate combinations. The paper concludes with a discussion of challenges for tillage researchers.
The effects of location (soil surface vs. incorporated in soil) and nature of plant residues on degradation processes and indigenous microbial communities were studied by means of soil microcosms incubation in which the different soil zones influenced by decomposition i.e. residues, soil adjacent to residues (detritusphere) and distant soil unaffected by decomposition (bulk soil) were considered. Plant material decomposition, organic carbon assimilation by the soil microbial biomass and soil inorganic N dynamics were studied with 13C labelled wheat straw and young rye. The genetic structure of the community in each soil zone were compared between residue locations and type by applying B- and F-ARISA (for bacterial- and fungal-automated ribosomal intergenic spacer analysis) directly to DNA extracts from these different zones at 50% decomposition of each residue. Both location and biochemical quality affected residue decomposition in soil: 21% of incorporated 13C wheat straw and 23% left at the soil surface remained undecomposed at the end of incubation, the corresponding values for 13C rye being 1% and 8%. Residue decomposition induced a gradient of microbial activity with more labelled C incorporated into the microbial biomass of the detritusphere. The sphere of influence of the decomposing residues on the dynamics of soluble organic C and inorganic N in the different soil zones showed particular patterns which were influenced by both residue location and quality. Residue degradation stimulated particular genetic structure of microbial community with a gradient from residue to bulk soil, and more pronounced spatial heterogeneity for fungal than for bacterial communities. The initial residue quality strongly affected the resulting spatial heterogeneity of bacteria, with a significance between-zone discrimination for rye but weak discrimination between the detritusphere and bulk soil, for wheat straw. Comparison of the different detrituspheres and residue zones (corresponding to different residue type and location), indicated that the genetic structure of the bacterial and fungal communities were specific to a residue type for detritusphere and to its location for residue, leading to conclude that the detritusphere and residue corresponded to distinct trophic and functional niches for microorganisms.
Microbial community composition may be an important determinant of soil organic matter (SOM) decomposition rates and nutrient turnover and availability in agricultural soils. Soil samples were collected from six long-term tillage comparison experiments located along two climatic gradients to examine the effects of no-tillage (NT) and conventional tillage (CT) management on bacterial and fungal abundance and biomass and to examine potential controls on the relative abundances of bacteria and fungi in these two systems. Samples were divided into 0–5 and 5–20 cm depth increments and analyzed for bacterial and fungal abundance and biomass, total C and N, particulate organic matter C and N (POM-C and N), soil water content, texture, pH, and water-stable aggregate distributions. Soil moisture, which varied by tillage treatment and geographically with climate, ranged from 0.05 to 0.35 g g−1 dry soil in the surface 0–5 cm and 0.15 to 0.28 g g−1 dry soil at 5–20 cm. Measured organic matter C and N fractions and mean weight diameter (MWD) of water-stable aggregates were significantly higher in NT relative to CT at three of the six sites. Fungal hyphal length ranged from 19 to 292 m g−1 soil and was 1.9 to 2.5 times higher in NT compared to CT surface soil across all sites. Few significant tillage treatment differences in soil physical and chemical properties or in fungal abundance and biomass were observed at 5–20 cm. Bacterial abundance and biomass were not consistently influenced by tillage treatment or site location at either depth. The proportion of the total biomass composed of fungi ranged from 10 to 60% and was significantly higher in NT compared to CT surface soil at five of six sites. Proportional fungal biomass was not strongly related to soil texture, pH, aggregation, or organic C and N fractions, but was positively related to soil moisture (r=0.67; P<0.001). The relationship between soil moisture and the degree of fungal dominance was due to the positive response of fungal biomass and the lack of response of bacterial biomass to increasing soil moisture across the range of measured soil water contents. Tillage treatment effects on fungal biomass and proportional fungal abundance were not significant when the data were analyzed by analysis of covariance with soil moisture as the covariate. These results suggest that observed tillage treatment and climate gradient effects on fungi are related to differences in soil moisture. Further research is needed, however, to determine how tillage-induced changes in the soil environment shape microbial community composition in agroecosystems.
Soil samples were taken from eight long-term agricultural monoculture and rotation experimental plots and examined for their profiles of fatty acids in either phospholipid or lipopolysaccharide fractions. The more specific constituents related to microorganisms were tested for their ability to estimate the biomass and to differentiate community structure.More than100 fatty acids, including unsubstituted, straight- and branched-chain,unsaturated and hydroxy fatty acids were detected in the soils sampled.Good correlations between the total amounts of fatty acids derived from phospholipids and the microbial biomasses and activities obtained by different classical procedures were observed (correlation coefficients were above 0.97). This indicates that the fatty acids were closely linked to soil microorganisms and that this method can be used in the study of soil microbial ecology.In addition,each of the eight soils was characterized by its own pattern of fatty acids, either as phospholipids,or as lipopolysaccharides.This shows that this method has the potential to differentiate between the soils,even on a management level.The most apparent difference was registered in terms of the relation of the monoenoic to the normal fatty acids among the eight soils.The black fallow and the fields cultivated with potatoes showed approximately equal amounts of both, the green fallow and the fields cultivated with wheat displayed a ratio of 1.7:1.0 and the grassland 1.3:1.0. The soil with crop rotation showed considerably more fatty acids in terms of the number in the normal fraction,while the grassland contained more hydroxy fatty acids than the soils from arable land.
Fungi and bacteria govern most of the transformations and ensuing long-term storage of organic C in soils. We assessed the relative contributions of these two groups of organisms to the microbial biomass and activity of soils from five different ecosystems with treatments hypothesized to enhance soil C sequestration: (1) desert (an elevation gradient allowed comparison of soil developed in a cooler, moister climate with soil developed in a warmer, drier climate), (2) restored tallgrass prairie (land reverted to native prairie in 1979 and neighboring land farmed to row crops for ∼100 year), (3,4) two forest types (Douglas fir and loblolly pine, unfertilized control and N-fertilized plots), and (5) agricultural land (conventional- and no-till management systems). The selective inhibition technique, using captan (fungicide) and oxytetracycline hydrochloride (bactericide), was used to determine the activities (respiration) of fungi and bacteria in each of these soils and substrate-induced respiration was used to measure total active soil microbial biomass C. Phospholipid fatty acid analysis was used to determine the composition of the soil microbial biomass and determine if the activities and structure of the microbial communities were related. Differences in fungal-to-bacterial (F:B) activities between treatments at a site were greatest at the prairie sites. The restored prairie had the highest F:B (13.5) and high total C (49.9 g C kg−1 soil); neighboring soil farmed to corn had an F:B of 0.85 and total C of 36.0 g C kg−1 soil. Within the pairs of study soils, those that were tilled had lower fungal activities and stored C than those that were managed to native or no-till systems. In all pairs of soils, soils that had higher absolute fungal activities also had more total soil C and when two extreme cases were removed fungal activity was correlated with total soil C (R2=0.85). Thus, in this small set of diverse soils, increased fungal activities, more than F:B ratios, were associated with increased soil C. Practices that involved invasive land management decreased fungal activity and stored soil C compared to similar soils that were less intrusively managed.
Fatty acid methyl esters (FAMEs) were used to ‘fingerprint’ soil microbial communities that evolved during 25 years of wheat-fallow cropping following native mixed prairie sod at Sidney, Nebraska, USA. Total ester-linked FAMEs (EL-FAMEs) and phospholipid-linked FAMEs (PL-FAMEs) were compared for their ability to discriminate between plots remaining in sod and those cropped to wheat or left fallow under no-till, sub-till or plow management. Cropped plots were higher in microbial biomass than their fallowed counterparts, and did not differ significantly with tillage for the 0–15 cm depth. Under fallow, microbial biomass was greatest in no-till and least in plow. Both cluster and discriminant analysis of PL- and EL-FAMEs clearly separated the remaining native sod plots from the existing wheat-fallow plots. This separation was particularly pronounced for the EL-FAMEs and was largely driven by high amounts in sod of a single FAME, C16:1(cis11), which has been cited as a biomarker for arbuscular mycorrhizal (AM) fungi. Within wheat-fallow, C16:1(cis11) declined significantly from no-till to plow, which supports the origin of C16:1(cis11) from extraradical mycelium and spores of AM fungi known to be sensitive to soil disturbance. Although discriminant analysis of PL- and EL-FAMEs differentiated wheat and fallow systems by tillage, discrimination among tillage treatments was expressed most strongly during fallow. FAME profiles from fallow plow were most dissimilar from cropped soils which suggests a relationship between tillage management and the long-term resiliency of the microbial community developed under the wheat crop.
Soil management practices affect soil microbial communities, which in turn influence soil ecosystem processes. In this study, the effects of conventional- (fall disking, chiseling and spring disking, field cultivation) and no-tillage practices on soil microbial communities were examined under long-term continuous cotton (Gossypium hirsutum L.) systems on a Decatur silt loam soil. Soil samples were taken in February, May, and October of 2000 at depths of 0–3, 3–6, 6–12, and 12–24 cm. Compared to the conventional-till treatment, the no-till treatment increased soil organic carbon and total nitrogen contents in the surface layer by 130 and 70%, respectively. Microbial biomass C content under no-till treatment was 60, 140, and 75% greater than under conventional-till treatment in February, May, and October, respectively. Principal components analysis of phospholipid ester-linked fatty acid (PLFA) profile indicated soil microbial communities shifted over time and with soil depth. This change appeared to be driven primarily by soil bacterial populations as indicated by the major PLFA contributors (i.e. fatty acids 16:0, 10Me16:0, cy19:0, 16:1 2OH, and i15:0) to the first two principal components. Tillage treatment differences were revealed by analysis of variance on the first principal components (PC 1), which accounted for 62% of the total sample variance, and by the relative abundance of selected PLFAs and PLFA ratios. The impact of tillage practices was significant in February and May, but not in October. During the growing season, changes in the microbial community may be primarily determined by soil conditions responding to cotton growth and environmental variables such as moisture and temperature; during fallow or prior to cotton establishment, community changes associated with tillage practices become more pronounced. These findings have implications for understanding how conservation tillage practices improve soil quality and sustainability in a cotton cropping system.
We investigated the effects of 13 yr of plow tillage (CT), no-tillage (NT), and ridge tillage (RT) on soil aggregation and moisture holding capacity under two cropping systems, corn (Zea mays L.) alone and cotton (Gossypium hirsutum L.) followed by corn at two depths. The experiment was conducted on an Hidalgo sandy clay loam (fine-loamy, mixed, active, hyperthermic Typic Calciustoll). Few cropping system differences were found. Aggregation was significantly greater at the 0- to 5-cm depth with NT and RT, especially in the >4750- and 500- to 212-μm size classes, where aggregate C and N contents were as much as 60% and >100%, respectively, higher than in CT. At 10 to 15 cm, CT produced greater aggregation in all but the >4750-μm size class but showed little enhancement of C and N retention compared with NT and RT. Mass-weighted data revealed a more biphasic retention of C and N at the 0- to 5-cm depth; more C and N were retained in the >4750- and 500- to 212-μm size classes at 0 to 5 cm. Most C and N was detected in the >4750-μm size fraction at the 10- to 15-cm depth. Water holding capacity was significantly greater with NT and RT by >12% over CT management. The beneficial effects of conservation tillage are directly related to soil content and accumulation of C and N. In this hot climate, in which crop residues are rapidly oxidized, soil C and N accretion rates with conservation tillage are slow but demonstrable.
Temperature is an important factor regulating microbial activity and shaping the soil microbial community. Little is known, however, on how temperature affects the most important groups of the soil microorganisms, the bacteria and the fungi, in situ. We have therefore measured the instantaneous total activity (respiration rate), bacterial activity (growth rate as thymidine incorporation rate) and fungal activity (growth rate as acetate-in-ergosterol incorporation rate) in soil at different temperatures (0-45 degrees C). Two soils were compared: one was an agricultural soil low in organic matter and with high pH, and the other was a forest humus soil with high organic matter content and low pH. Fungal and bacterial growth rates had optimum temperatures around 25-30 degrees C, while at higher temperatures lower values were found. This decrease was more drastic for fungi than for bacteria, resulting in an increase in the ratio of bacterial to fungal growth rate at higher temperatures. A tendency towards the opposite effect was observed at low temperatures, indicating that fungi were more adapted to low-temperature conditions than bacteria. The temperature dependence of all three activities was well modelled by the square root (Ratkowsky) model below the optimum temperature for fungal and bacterial growth. The respiration rate increased over almost the whole temperature range, showing the highest value at around 45 degrees C. Thus, at temperatures above 30 degrees C there was an uncoupling between the instantaneous respiration rate and bacterial and fungal activity. At these high temperatures, the respiration rate closely followed the Arrhenius temperature relationship.
- Dighton
Fungal-to-bacterial ratios in soils investigated for enhanced C sequestration
- Bailey