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Density fractions of macro-organic matter and microbial biomass as predictors of C and N mineralization
Abstract
Macroorganic matter of arable soils which had received different inputs of organic residues for 25 y and grassland soils that had been under grass for at least 8 y was fractionated into light, intermediate and heavy fractions using a stable silica suspension as heavy liquid. For all residue treatments, the C-to-N ratios of organic matter decreased in the order light, intermediate, heavy macroorganic matter (fraction > 150 μm) and non-macroorganic matter (fraction < 150 μm). Residue application had a stronger effect on the amount and C-to-N ratio of macroorganic matter fractions than on the amount and C-to-N ratio non-macroorganic matter. Textural effects were apparent with the proportions of soil N in the light and intermediate fractions being higher in coarse-textured grassland soils than in fine-textured grassland soils. C and N mineralization were positively correlated with the amount of C and N in the light fraction and the active microbial biomass. The correlation with mineralization decreased with increasing stability of the organic matter fractions. C and N mineralization per unit of total microbial biomass were lower in fine-textured soils than in coarse-textured soils. This is ascribed to a greater physical protection of the organic matter in fine-textured soils than in coarse-textured soils.
... The soil organic carbon was determined as per Walkley and Black's rapid titration method by [8]. To determine the particulate organic carbon was separated by dispersing the 50 g of the respective soil sample with 150 ml of 0.5% sodium hexametaphosphate solution and shaking for 15 h on a reciprocal shaker as described by [9], [10]. To determine the aggregate associated organic carbon was air dried soil sample through a 2-mm sieve and after the oven-dried at 50°C of respective soil samples for analyzed the Walkley and Black's rapid titration technique by [8]. ...
... The deeper root biomass of trees in forest and horticulture soil might have increased the SOC accumulation in the subsurface layers. The lowest soil organic carbon content in degraded land may be due to poor growth and scanty vegetation, negligible forest leaf litter, vis-à-vis overgrazing and highly eroded nature of these soils [10]. The pasture soil had higher SOC concentration than that of cropland soils because of continuous plant carbon inputs from above and below ground biomass and reduced rate of mineralization from decreased soil disturbance [3], [9]. ...
Soil aggregates and organic matter are measured to be essential indicators of soil quality. The objective of this study was to determine landuse effects on the distribution of soil organic carbon (SOC) associated with aggregate size fractions. Bulk soil samples were collected from incremental soil depth (0-15, 15-30, 30-60 and 60-100 cm) under five landuse systems; forest, horticulture, agriculture, pasture and degraded lands. Soil samples collected from these landuse were analyzed for aggregate stability after dry and wet sieving into three aggregate size classes (2.0 mm, 2.0-0.25mm and <0.25 mm) and the concentration of SOC fractions in each landuse. Bulk densities were greater in degraded land (1.54-1.57 g cm-3) than agriculture lands (1.52-1.53g cm-3). The macro-aggregates (˃2.0 m) were higher in surface soil of pasture, agriculture and degraded whereas subsurface soil layer were higher in forest and horticulture land. Aggregate stability varied in the order of pasture˃forest˃horticulture˃agriculture ˃degraded lands in surface soil. SOC fraction decreased with increasing soil depth under different landuse systems. Our data supported the hypothesis that vegetation (fruit tree plantation) landuse systems and the proportion of aggregates are suitable indicators of SOC build-up and may therefore have a better potential for SOC sequestration than the degraded land.
... Hassink (1992) reported higher mineralization of C and nitrogen for soils with a coarser texture than that of soils with finer texture. These results tend to improve the ability of soils with a fine texture to protect OC physically from the attack of microbes (Hassink 1995). The texture of the soil is majorly responsible for C stabilization at shallow depths of land types such as lands for forest, crops, and shrubs (Fontaine et al. 2007;Albaladejo et al. 2013). ...
... The organic matter in coarse-textured soils decomposes relatively faster than available in fine-textured soils (Hassink 1992). This may be attributed by OC being physically protected against microbial attack by fine-textured soils (Hassink 1995). Almost in every land use, the texture of the soil is important in the preservation of organic matter (e.g., in cropland, forest land, shrub land) in the lower soil depths (Albaladejo et al. 2013;Fontaine et al. 2007). ...
... Physical fractionation of soils was done to comprehend soil structure and C distribution within aggregates and in attachment with mineral matrix [35,36,38,54]. In density fractionation, heavy density fraction represented humified/ amorphous organic matter attached to soil mineral matrix [55] whereas light density fraction represented loose and undecomposed plant/ organic residues [55,56]. Continuous fresh organic matter addition in forest soils by leaf-litter fall possibly caused the comparative higher light density fractions there. ...
... Physical fractionation of soils was done to comprehend soil structure and C distribution within aggregates and in attachment with mineral matrix [35,36,38,54]. In density fractionation, heavy density fraction represented humified/ amorphous organic matter attached to soil mineral matrix [55] whereas light density fraction represented loose and undecomposed plant/ organic residues [55,56]. Continuous fresh organic matter addition in forest soils by leaf-litter fall possibly caused the comparative higher light density fractions there. ...
Indian soils are inherently poor in quality due to the warm climate and erosion. Conversion of land uses like forests to croplands and faulty management practices in croplands further cause soil degradation. This study aimed to understand the extent of these impacts in a small representative part of eastern India, covering Himalayan terai and nearing alluvial plains. Soils were collected from (i) forests, (ii) croplands (under agricultural practices for more than 50–60 years) and (iii) converted lands (converted from forests to croplands or tea gardens over the past 15–20 years). Different soil quality indicators were assessed and soil quality index (SQI) was generated to integrate, scale and allot a single value per soil. Results indicated that continuous organic matter deposition and no disturbances consequence the highest presence of soil carbon pools, greater aggregation and maximum microbial dynamics in forest soils whereas high application of straight fertilizers caused the highest available nitrogen and phosphorus in cropland soils. The SQI scorebook indicated the best soil quality under forests (x¯ 0.532), followed by soils of converted land (x¯ 0.432) and cropland (x¯ 0.301). Comparison of the SQI spatial distribution with land use and land cover confirmed the outcome. Possibly practices like excessive tillage, high cropping intensity, no legume in crop rotations, cultivation of heavy feeder crops caused degraded soil quality in croplands. This study presented an example of soil quality degradation in India due to land use change and faulty management practices. Such soil degradation on a larger scale may affect future food security.
... Hassink (1992) reported higher mineralization of C and nitrogen for soils with a coarser texture than that of soils with finer texture. These results tend to improve the ability of soils with a fine texture to protect OC physically from the attack of microbes (Hassink 1995). The texture of the soil is majorly responsible for C stabilization at shallow depths of land types such as lands for forest, crops, and shrubs (Fontaine et al. 2007;Albaladejo et al. 2013). ...
... The organic matter in coarse-textured soils decomposes relatively faster than available in fine-textured soils (Hassink 1992). This may be attributed by OC being physically protected against microbial attack by fine-textured soils (Hassink 1995). Almost in every land use, the texture of the soil is important in the preservation of organic matter (e.g., in cropland, forest land, shrub land) in the lower soil depths (Albaladejo et al. 2013;Fontaine et al. 2007). ...
Carbon stabilization involves to capturing carbon from the atmosphere and fix it in the forms soil organic carbon stock for a long period of time, it will be present to escape as a greenhouse gas in the form of carbon dioxide. Soil carbon storage is an important ecosystem service, resulting from interactions of several ecological processes. This process is primarily mediated by plants through photosynthesis, with carbon stored in the form of soil organic carbon. Soil carbon levels have reduced over decades of conversion of pristine ecosystems into agriculture landscape, which now offers the opportunity to store carbon from air into the soil. Carbon stabilization into the agricultural soils is a novel approach of research and offers promising reduction in the atmospheric carbon dioxide levels. This book brings together all aspects of soil carbon sequestration and stabilization, with a special focus on diversity of microorganisms and management practices of soil in agricultural systems. It discusses the role of ecosystem functioning, recent and future prospects, soil microbial ecological studies, rhizosphere microflora, and organic matter in soil carbon stabilization. It also explores carbon transformation in soil, biological management and its genetics, microbial transformation of soil carbon, and their role in sustainable agriculture. The book offers a spectrum of ideas of new technological inventions and fundamentals of soil sustainability. It will be suitable for teachers, researchers, and policymakers, undergraduate and graduate students of soil science, soil microbiology, agronomy, ecology, and environmental sciences
... Hassink (1992) reported higher mineralization of C and nitrogen for soils with a coarser texture than that of soils with finer texture. These results tend to improve the ability of soils with a fine texture to protect OC physically from the attack of microbes (Hassink 1995). The texture of the soil is majorly responsible for C stabilization at shallow depths of land types such as lands for forest, crops, and shrubs (Fontaine et al. 2007;Albaladejo et al. 2013). ...
... The organic matter in coarse-textured soils decomposes relatively faster than available in fine-textured soils (Hassink 1992). This may be attributed by OC being physically protected against microbial attack by fine-textured soils (Hassink 1995). Almost in every land use, the texture of the soil is important in the preservation of organic matter (e.g., in cropland, forest land, shrub land) in the lower soil depths (Albaladejo et al. 2013;Fontaine et al. 2007). ...
Fixation of carbon dioxide (CO2) for the production of organic compounds is carried out globally by microbes. These microbes provide food for the survival of heterotrophs in terms of organic C through CO2 fixation. The most familiar pathway of carbon (C) fixation is Calvin–Benson–Bassham cycle. This pathway is adopted by plants, microbes, and algae for inorganic C fixation in natural environment. However, there are a number of other pathways as well that are specifically adopted by microbes for C fixation. By adopting these pathways, microbes follow diversified chemical and biochemical strategies. This chapter is providing basic knowledge about the fixation of CO2 by microbes, mechanism involved in the fixation of CO2, and the enzymes which regulate these mechanisms. Five major pathways, i.e., Calvin-Benson-Bassham cycle, reductive tricarboxylic acid cycle, 3-hydroxypropionic acid (3-HP) cycle, reductive acetyl-CoA (rACo) pathway, and carboxylases, are discussed in this chapter. Four C-fixing pathway enzymes have been described in the chapter. In the near future, it is expected that new pathways will also be established due to number and diversity of microorganisms.
... Hassink (1992) reported higher mineralization of C and nitrogen for soils with a coarser texture than that of soils with finer texture. These results tend to improve the ability of soils with a fine texture to protect OC physically from the attack of microbes (Hassink 1995). The texture of the soil is majorly responsible for C stabilization at shallow depths of land types such as lands for forest, crops, and shrubs (Fontaine et al. 2007;Albaladejo et al. 2013). ...
... The organic matter in coarse-textured soils decomposes relatively faster than available in fine-textured soils (Hassink 1992). This may be attributed by OC being physically protected against microbial attack by fine-textured soils (Hassink 1995). Almost in every land use, the texture of the soil is important in the preservation of organic matter (e.g., in cropland, forest land, shrub land) in the lower soil depths (Albaladejo et al. 2013;Fontaine et al. 2007). ...
In the presented chapter, various aspects related to carbon stabilization and storage in the form of biochar (an important soil amendment) are discussed. The following questions were considered: (i) what is the current general knowledge on biochar and its physicochemical composition, (ii) how manufacturing conditions affect biochar characteristics, including their role in carbon stabilization, (iii) how biochar contributes to soil carbon balance and storage, (iv) what are the effects of biochar on water retention in soil, soil erosion, production yields and economic productivity in agriculture, (iv) what are the effects of biochar on soil microbial community and activity, and (v) how biochar affects other soil amendments and their roles in soil. The present studies assess scientific outcomes and results which conclude that soil organic matter gained by organic residues can be used to enhance soil carbon storage. Following the published scientific results, the biochar amendment appears to be a promising way for increasing the stocks of recalcitrant carbon in the soil from a long-term perspective. Future research should focus on the designing, production, and use of enriched biochar, e.g. with nutrients, minerals, or microorganisms, to improve soil physicochemical properties, supply nutrients, and prevent their leaching. The fertilizer supplies accessible nutrients available to plants, and biochar can sequester depleted elements and prevent leaching of the added ones.
... Hassink (1992) reported higher mineralization of C and nitrogen for soils with a coarser texture than that of soils with finer texture. These results tend to improve the ability of soils with a fine texture to protect OC physically from the attack of microbes (Hassink 1995). The texture of the soil is majorly responsible for C stabilization at shallow depths of land types such as lands for forest, crops, and shrubs (Fontaine et al. 2007;Albaladejo et al. 2013). ...
... The organic matter in coarse-textured soils decomposes relatively faster than available in fine-textured soils (Hassink 1992). This may be attributed by OC being physically protected against microbial attack by fine-textured soils (Hassink 1995). Almost in every land use, the texture of the soil is important in the preservation of organic matter (e.g., in cropland, forest land, shrub land) in the lower soil depths (Albaladejo et al. 2013;Fontaine et al. 2007). ...
In the last decades, many studies were addressed focusing on soil protection that helps sequestration and stabilization of organic carbon in soil aggregates. Soil aggregates are an association of primary soil particles, bacteria, fungi, plant root and soil organic matter. Plant root provides a carbon source for arbuscular mycorrhizal fungi (AMF) present in soil aggregates. AMF produces a glycoprotein glomalin which is hydrophobic, insoluble, and recalcitrant in nature. Glomalin plays a vital role in the stabilization of soil aggregates. Greater stability of soil aggregates leads to a larger amount of protected organic carbon in the soil. Thus, glomalin-related soil protein can be considered as a potential contributor in the stabilization of soil organic carbon. In the present chapter, the different aspects of glomalin composition, production, role in soil, recalcitrant nature, potential role in soil carbon locking up and stabilization are summarized and discussed.
... Specifically, C stored in fine fractions is more recalcitrant than C stored in larger fractions and represents the stable fractions (Bronick and Lal, 2005;Rita et al., 2011) with longer turnover times ranging from decades to centuries (Haile et al., 2008;Yamashita et al., 2006). Furthermore, soil C in the heavy density (>1.6 g cm − 3 ) fraction is generally more stable because of the presence of less mineralizable C than in the light density (<1.6 g cm − 3 ) fraction (Christensen, 1992;Hassink, 1995). Higher stability ensures C sequestration for long periods within the ecosystem and helps offset CO 2 emission (Haile et al., 2008). ...
Grassland soils play an important role in sequestering carbon (C) and are primarily used for livestock grazing. Grazing management can increase the amount of C stored in soils and the distribution of C in different soil fractions by altering soil microbial community structure, thereby influencing the persistence of soil C over time. Adaptive multi-paddock grazing (AMP), grazing cattle at high stock densities with long periods between grazing events, is considered to enhance grassland sustainability, productivity, and soil C compared to more conventional grazing practices (continuous to slow rotational). However, whether and how AMP grazing might affect the amount of C stored in different soil fractions has received little attention. Soil samples (0-15 cm depth) were collected from 24 ranches in a paired design, where 12 ranches practiced AMP grazing and 12 neighboring ranches practiced conventional grazing. Soil organic C (SOC) and total nitrogen were measured in different soil particle size [fine (<53 µm), medium (53-250 µm) and coarse (>250 µm)], and density [light (>1.6 g cm − 3), and heavy (<1.6 g cm − 3)] fractions. Soil bacterial and fungal biomass and abundances were obtained from phos-pholipid fatty acid analysis. Mean weights of soil microaggregates and heavy fractions were higher in soil exposed to AMP grazing, whereas mean weights of macroaggregates and light fractions were higher in conventionally grazed soils. In warmer and drier climatic conditions, SOC in both bulk soils and within various size and density fractions tended to decrease. Soil organic C (both concentration and stock) were significantly higher in the fine soil fractions under AMP management than conventionally grazed grasslands. Given that SOC in fine fractions, is more mineral associated and recalcitrant, our results indicate that AMP grazing increased the size of the stable SOC pool. The increased carbon pool in the fine fraction was associated with greater fungal to bacterial ratios, suggesting a possible biological mechanism for the increase. Overall, the results indicate that AMP grazing may be beneficial for sequestering more stable carbon that helps mitigate the effects of climate change.
... When soil microbial carbon content increases, microbial activity and quantity increase, leading to the decomposition of organic matter by microorganisms. In this process, microorganisms consume organic matter through respiration and release gases such as carbon dioxide, which leads to ER enhancement [51]. The root system of alfalfa is developed, and the root system secretes a variety of substances during the growth process. ...
Cultivated grasslands are an important part of grassland ecosystems and have been proven to be major carbon sinks, then playing an important role in the global carbon balance. The effect of cultivated grassland type (Medicago sativa, Triticum aestivum, Secale cereale, and Vicia villosa grasslands) on carbon flux (including net ecosystem CO2 exchange (NEE), ecosystem respiration (ER), and gross ecosystem productivity (GEP)) downstream of the Yellow River was studied via the static chamber technique and a portable photosynthetic system. Bare land was used as a control. The results showed that the four cultivated grassland types were mainly carbon sinks, and bare land was a carbon source. The cultivated grassland types significantly affected carbon flux. The average NEE and GEP of the grassland types were in the following order from high to low: Medicago sativa, Secale cereale, Triticum aestivum, and Vicia villosa grassland. Stepwise regression analysis showed that among all measured environmental factors, soil pH, soil bulk density (BD), soil organic carbon (SOC), and soil microbial carbon (MBC) were the main factors affecting CO2 flux. The combined influence of soil BD, SOC, and pH accounted for 77.6% of the variations in NEE, while soil BD, SOC, and MBC collectively explained 79.8% of changes in ER and 72.9% of the changes in GEP. This finding indicates that Medicago sativa grassland is a cultivated grassland with a high carbon sink level. The changes in carbon flux were dominated by the effects of soil physicochemical properties.
... In contrast, the >150 μm size fraction was considered labile organic N. Both fractions contain nitrogenous organic compounds and microbial biomass N (Hassink, 1995). The physical fractionation of different functional organic N fractions has been well used in macro-modeling and empirical studies (Huygens et al., 2007;Rütting et al., 2008;Zimmermann et al., 2007). ...
Soil organic nitrogen (N) mineralization not only supports ecosystem productivity but also weakens carbon and N accumulation in soils. Recalcitrant (mainly mineral-associated organic matter) and labile (mainly particulate organic matter) organic materials differ dramatically in nature. Yet, the patterns and drivers of recalcitrant (MNrec) and labile (MNlab) organic N mineralization rates and their consequences on ecosystem N retention are still unclear. By collecting MNrec (299 observations) and MNlab (299 observations) from 57 15N tracing studies, we found that soil pH and total N were the master factors controlling MNrec and MNlab, respectively. This was consistent with the significantly higher rates of MNrec in alkaline soils and of MNlab in natural ecosystems. Interestingly, our analysis revealed that MNrec directly stimulated microbial N immobilization and plant N uptake, while MNlab stimulated the soil gross autotrophic nitrification which discouraged ammonium immobilization and accelerated nitrate production. We also noted that MNrec was more efficient at lower precipitation and higher temperatures due to increased soil pH. In contrast, MNlab was more efficient at higher precipitation and lower temperatures due to increased soil total N. Overall, we suggest that increasing MNrec may lead to a conservative N cycle, improving the ecosystem services and functions, while increasing MNlab may stimulate the potential risk of soil N loss.
... Among soil factors, texture plays an important role in C sequestration. More mineralization of C and N was recorded in coarse-textured soils compared to fine-textured soils (Hassink, 1992), which could be due to the greater ability of fine-textured soils to physically protect SOC against microbial attack (Hassink, 1995). Chemical adsorption of C onto the surface of clays and clay minerals and physical occlusion within microaggregates (Sissoko and Kpomblekou-A, 2010;Singh et al., 2018) make SOC inaccessible to microbial degradation in clay-dominated soils. ...
Carbon (C) sequestration in soil is limited by the soil's maximum C carrying capacity (C m) and C saturation deficit (S d). These two parameters have enormous implication for choosing appropriate management strategies to increase a soil's C sequestration potential (CSP). The present study aims to estimate the C m and S d of two Alfisols from Bhubaneswar (Alfisol-BHNS) and Pattambi (Alfisol-PTMB) and two Vertisols from Parbhani (Vertisol-PRBN) and Junagadh (Vertisol-JNGD) in India with a history of long-term manuring and fertilization practices. Both the Alfisols maintained a rice-rice cropping system whereas the Vertisols had a soybean-safflower and groundnut-wheat cropping system, respectively. Irrespective of soil types and cropping systems, the soil organic C (SOC) content and stock were the highest in the treatment receiving 100% of recommended dose of NPK combined with 10 Mg ha-1 well decomposed farmyard manure (100%NPK+FYM). The mean annual estimated return of C (MAERC) across the soil types followed the order 100%NPK + FYM> 150%NPK = 100%NPK +Lime (Agricultural grade, purity 80%)> 100%NPK > 50%NPK > control. The C m at 0-30 cm soil depth was 39.3, 21.7, 47.6 and 25.0 Mg ha-1 , respectively for Alfisol-PTMB, Alfisol-BHNS, Vertisol-JNGD and Vertisol-PRBN. The S d value was the highest in the control treatment and lowest in100% NPK + FYM treatment, signifying a higher CSP of the former soil than the later. Therefore, 100%NPK +FYM treatment would require a minimum threshold level of C addition to maintain the SOC at equilibrium. The estimated minimum threshold limit of annual C input (A E) to preserve the existing SOC level was 1.84, 0.39, 1.57 and 0.90 Mg ha-1 yr-1 for Alfisol-PTMB, Alfisol-BHNS, Vertisol-JNGD and Vertisol-PRBN, respectively. Alfisol-PTMB and Vertisol-JNGD showed a higher CSP than Alfisol-BHNS and Vertisol-JNGD because the former two soils had higher S d values than the later soils. The MAERC, climate, soil texture and clay mineralogy largely influenced the SOC sequestration and C m values. An integrated application of 100%NPK with either lime or FYM is recommended to maintain the sequestration and stabilization of SOC in the studied soils. The CSP of the soils could be further increased via innovative approaches such as increasing soil's reactive mineral contents to lock additional C.
... Research suggest that tillage can lead to soil compaction and reduced permeability, resulting in an increased runoff, soil erosion, and nutrient losses (Gliessman, 2014;Gomiero, 2016;Lal et al., 2007;Montgomery, 2007;Nearing, 2013), see ( Figure 2). Additionally, tillage has been linked to decreased soil organic matter, which can further reduce soil fertility (Feller et al., 2020;Hassink, 1995;Huggins & Reganold, 2008;Six et al., 2000;West et al., 2002). Due to the harmful effect of tillage, no-till practices are increasingly implemented in agricultural fields (Islam & Reeder, 2014). ...
Societal Impact Statement
Transformative agricultural strategies like agrivoltaics (AV) are essential for addressing the pressing global issues of sustainable energy and food production in a changing climate. Conservation‐agrivoltaics (Conservation‐AV) provides the potential to meet these needs while reinforcing natural resources and protecting the environment. It could enhance the ecological benefits of AV by improving soil health and biodiversity. It could create economic opportunities for farmers and increase the resilience and diversity of food crops under changing climate conditions. Furthermore, it could inform stakeholders about the benefits and challenges of implementing conservation agriculture management practices (CAMP) in AV and encourage further exploration and adoption of this innovative approach.
Summary
Transformative strategies in agriculture are needed to address urgent global challenges related to energy and food production while reinforcing natural resources and the environment. Agrivoltaics (AV) has emerged in the past decade as one solution to this fundamental challenge of improving energy and food security. AV is defined as the co‐location of solar photovoltaic (PV) panels and crops on the same land to optimize food and energy production simultaneously and sustainably. Here, we propose that AV, together with conservation agriculture management practices (CAMP) strategies can help to intensify food security and energy production while reinforcing natural resources and the environment. Our main assertions in this opinion article are that: (1) AV systems need to overcome several agronomical, environmental, and ecological challenges to intensify food and energy production sustainably; (2) CAMP applied to AV systems can preserve the environment and ensure climate‐resilient food production; (3) implementation of CAMP in AV can lead to long‐term carbon sequestration, lower greenhouse gas emissions, and maintain or increase crop yields while preserving soil health and biodiversity; and (4) adoption of CAMP in AV can bring economic benefits, although challenges need to be overcome. This opinion article proposes a new ecosystem approach to integrate renewable energy and sustainable food production and encourages research on the effects of CAMP on AV systems.
... However, the ratio of min-C in the 0-to 5-cm depth increment to the 5-to 10-cm depth ranged from 2.3 to 3.6, and the ratio of soil organic matter in the 0-to 5-cm depth increment to the 5-to 10-cm depth ranged from 1.0 to 2.0. This could be explained as different soil biological properties at two soil depths, including microbial biomass (Hassink, 1995) and soil organic C content (Nelson & Sommers, 1983). Nitrogen fertilizer rate had no effect on min-C, regardless of root zones (Table 2). ...
A rapid soil test for accurately estimating nitrogen (N) supply from soil organic matter would help turfgrass managers develop N fertilization programs. In this study, we tested the feasibility of using a quick test, mineralizable carbon (min‐C), to predict turfgrass growth and N uptake from sand‐based putting green soils. A 2‐year field experiment was conducted in Verona, WI, on four sand‐based research golf greens planted with creeping bentgrass. Nitrogen fertilizer was applied at 0, 10, and 20 kg ha⁻¹ every 2 weeks as liquid urea during the growing seasons. Soil samples were collected at 0–5 cm and 5–10 cm and tested for min‐C by measuring the flush of CO2 following the rewetting dried soil, where the soil was rewetted at 50% water‐filled pore space and incubated at 25°C for 24 h. Min‐C was greater at the shallower soil depth, and unaffected by N rates that were applied. On‐site air temperature, soil moisture content, and estimated soil temperature were negatively related with min‐C, where r² = 0.26–0.60 for air temperature, r² = 0.32–0.71 for soil moisture content, and r² = 0.16–0.53 for estimated soil temperature, indicating the test is quite sensitive to environmental conditions at the time of sampling. Furthermore, min‐C had weak positive to no relationship with creeping bentgrass growth rate (r² = 0–0.17) and N uptake (r² = 0–0.23) on sand‐based putting green, suggesting the test does not hold promise as a method for improving fertilizer decisions to these systems.
... In addition, different soil textures also play a core role for GHG production and emissions, for example, the size of soil particles, the specific surface area of soil particles and the ability of the surface to absorb ions will be different. Fine-grained sediments tend to have relatively low carbon mineralization per unit of biomass due to their stronger protective effect on soil OM (Hassink, 1995), thus further investigation for the sediment properties has to be addressed in great details. ...
... The root biomass might have increase the soil organic carbon accumulation in the subsurface layer. The lowest soil organic carbon content in overgrazing prevention may be due to poor growth, high runoff and high soil erosion, Hassink [21] and Sollins et al. [22]. Soil organic carbon was highest in cover crop as compared to other resource conservation techniques and results were consistent with the findings of Nagaraja et al. [23] and Kumar et al. [24]. ...
The present study highlights the impact of resource conservation techniques on soil properties in sub montane north western Himalayas. The continued maintenance of fertile soil is essential in order to meet basic human needs. The topography of the region ranging from gently sloping to moderately-steep sloping retards the vertical development of soils. The study was conducted in the Merth village of state J&K. The experiment was laid out to compare the impact of resource conservation techniques on the runoff and sediment yield in two different catchment areas (one with sandy loam texture and other with clay loam texture) in monsoon season. The slope of the catchment areas varies from 3-6%. The increase in available nitrogen in sandy and clay loam can be attributed because of the increase in root biomass under resource conservation techniques. Addition of root biomass and litter fall in cover crop indirectly through the process of mineralization increases the availability of available nitrogen. The soils of submontane Shivaliks are under tremendous stress because of high soil erosivity and poor soil management practices. The study strongly recommends adoption of resource conservation techniques for reducing soil erosion & water conservation in submontane Shivaliks.
... The presence of root biomass and leaf litter in cover crop might have contributed to the high soil organic carbon content, particularly in the subsurface layer. On the other hand, the poor growth, high runoff, and soil erosion in overgrazing prevention could have led to the lowest soil organic carbon content, as suggested by Hassink [37] and Sollins et al. [38]. The results showed that cover crop had the highest soil organic carbon content compared to other resource conservation techniques, which is consistent with the findings of Nagaraja et al. [39] and Kumar et al. [40]. ...
The present study uncovering the impact of erosion conservation techniques on soil attributes in Shivaliks of lower Himalayas of Jammu. Soil erosion is considered as the main cause of land degradation in hilly areas espially in outer Himalayas. Although the problem persisted on the earth for a longer period, it has become severe in recent times due to increased man-environment interactions. The study was conducted in 2021 at the Merth village of Jammu and Kashmir, India, which is situated in the Kathua district. The catchment area investigated had a clay loam texture and a slope gradient of 3-6%, with a total area of 24.8 acres. The result shows that mean value of bulk density under various erosion control techniques was highest in overgrazing prevention (1.40g cm-3) followed by perimeter runoff control, terrace farming and contour plowing and was lowest in cover crop (1.33g cm-3). The carbon content also increased with the and was highest under cover crop. Carbon act as bridge between nutrient, water and soil. The study strongly recommends adoption of resource conservation techniques for reducing soil erosion & water conservation in submontane Shivaliks.
... It is well known that mineralization of C is highly expressed in coarse-textured soils compared to fine-textured soils (Hassink 1992;Singh et al. 2017). These results could be due to the greater ability of fine-textured soils to physically protect the SOC from microbial attack (Hassink 1995;Singh et al. 2017). It also plays an important role in C stabilization in the lower soil depths under all land uses (Fontaine et al. 2007;Albaladejo et al. 2013;Singh et al. 2017). ...
The present work was designed to study a soil sequence in Mount Mandara, in order to identify the influence of altitude, soil characteristics, and land use on the accumulation of soil organic carbon (SOC). The study was conducted in four sites in the Far-North region of Cameroon, including Zamai, Kossohone, Sir, and Rhumsiki. Three pits were dug down to the weathering horizons in three positions (upslope, mid-slope, and footslope) along a representative toposequence in each site. Samples were taken from each pit at regular increment of 25 cm from the soil surface. The total SOC stock (T-SOCS) contents are 128.63 ± 5.25 Mg ha−1 in Arenosols at Zamai (608 m a.s.l.), 158.248 ± 10.52 Mg ha−1 in Leptosols at Kosohone (865 m a.s.l.), 158.99 ± 13.25 Mg ha−1 in Luvisols at Sir (970 m a.s.l.), and 144.79 ± 24.23 Mg ha−1 in Regosols at Rhumsiki (1050 m a.s.l.). The main secondary minerals are smectite, kaolinite, sepiolite, lepidocrocite, hematite, and calcite. Clay minerals and iron oxides are good receptacle for SOC and might constitute a major asset for the accumulation and the sequestration of SOC. Increase in elevation leads to decrease in the annual temperature which affect microbial activity, leading thus to a slow rate of soil organic matter (SOM) decomposition, which thereby affected SOCS. This is confirmed by the significant correlation between altitudinal gradient and T-SOCS (r = 0.70), with altitude contributing to the accumulation of SOC for 49.68%. Texture also plays a central role in carbon sequestration in the studied area, confirmed by the significant and positive correlation between silt fraction and SOM. Under Regosols, there is a decrease in T-SOCS value as a result of a reduction of the quantity of organic matter returned to the soil and more rapid SOM decomposition due to ploughing. This research provides a preliminary assessment for SOC stock at Mount Mandara. It suggests that altitudinal gradient, land use, and soil characteristics should be included in SOCS models and estimations at local and regional scales.
... Our findings stay in contrast to results of Wang et al. (2017), who found that sand addition had no effect on DNRA and I NO 3 in a subtropical forest. Litter materials of forests are decomposed more rapidly in sandy soils than in clay soils (Marhan & Scheu, 2005), indicating that soil microorganisms are more active in sandy soil than in clay soils (Hassink, 1995), stimulating soil I NO 3 . Future studies on soil gross N transformation rates in tropical and subtropical regions could therefore benefit from taking soil texture into account. ...
Tropical and subtropical forest biomes are a main hotspot for the global nitrogen (N) cycle. Yet, our understanding of global soil N cycle patterns and drivers and their response to N deposition in these biomes remains elusive. By a meta-analysis of 2426-single and 161-paired observations from 89 published 15 N pool dilution and tracing studies, we found that gross N mineralization (GNM), immobilization of ammonium (INH4 ) and nitrate (INO3 ), and dissimilatory nitrate reduction to ammonium (DNRA) were significantly higher in tropical forests than in subtropical forests. Soil N cycle was conservative in tropical forests with ratios of gross nitrification (GN) to INH4 (GN/INH4 ) and of soil nitrate to ammonium (NO3 - /NH4 + ) less than one, but was leaky in subtropical forests with GN/INH4 and NO3 - /NH4 + higher than one. Soil NH4 + dynamics were mainly controlled by soil substrate (e.g., total N), but climatic factors (e.g., precipitation and/or temperature) were more important in controlling soil NO3 - dynamics. Soil texture played a role, as GNM and INH4 were positively correlated with silt and clay contents, while INO3 and DNRA were positively correlated with sand and clay contents, respectively. The soil N cycle was more sensitive to N deposition in tropical forests than in subtropical forests. Nitrogen deposition leads to a leaky N cycle in tropical forests, as evidenced by the increase in GN/INH4 , NO3 - /NH4 + and nitrous oxide emissions and the decrease in INO3 and DNRA, mainly due to the decrease in soil microbial biomass and pH. Dominant tree species can also influence soil N cycle pattern, which has changed from conservative in deciduous forests to leaky in coniferous forests. We provide global evidence that tropical, but not subtropical, forests are characterized by soil N dynamics sustaining N availability and that N deposition inhibits soil N retention and stimulates N losses in these biomes.
... Our results showed that root-C and -N were the principal factors that explained increases in MBC. The intimate contact of roots with the soil matrix, the accessibility of particulate material, and the chemical signals of root exudates explain this relationship between the root system and microbial biomass and activity, since roots are the most important substrate for soil organisms (Hassink, 1995;Williams and Vries, 2020). Therefore, including cover crops and pasture in the rotation provides for a living root system throughout the year which favored higher levels of microbial biomass in comparison with the soybean monoculture, where the large fallow period produced starvation of the microbial population due to the lack of root substrate (Blagodatskaya and Kuzyakov, 2013;Finn et al., 2017). ...
... POC and MOC were estimated as per the method described by Cambardella and Elliott (1992) and Hassink (1995). Soil (50 g) was dispersed in 150 ml of 0.5% sodium hexametaphosphate solution by shaking for 15 h on a reciprocal shaker. ...
The long-term effect of organic farming practices were evaluated on soil organic carbon stocks (SCS) and its fractions in texturally divergent soils of Haryana. Surface (0-15 cm) soil samples were collected from 25 organic farms and adjoining conventional farms from 11 districts of Haryana. Soil samples were analyzed for pH, EC, calcium carbonate (CaCO3), soil organic carbon (SOC) and its fractions, viz. light fraction C (LOC), particulate organic C (POC) and mineral associated C (MOC). Results revealed that shifting from conventional to organic farming had no effect on soil pH and EC but reduced the CaCO3 significantly (P<0.05). Soil under organic farming exhibited a significant increase in the SOC from 5.1 to 6.2 g/kg and SCS from 11.2 to 13.3 Mg/ha as compared to soils under conventional farming. The light fraction C was most sensitive to management practices, followed by POC and MOC fraction. The magnitude of increase in LOC, POC and MOC under organic soils was 48.9, 23.6 and 14.7%, respectively as compared to conventionally managed soils. Different organic carbon pools in various fractions followed the order MOC> POC> LOC. The study concluded that shift from conventional to organic farming could be adopted or promoted for sustainable management of soil organic C stocks.
... Additionally, lignin and aromatic SOM seem to adsorb onto coarse silt and sand fractions, as finer textured soils have lower lignin concentration as a proportion of total SOM (Han et al., 2016). Sand is associated with increased and faster decomposition of labile SOM (Marhan and Sheu, 2004), likely due to increased microbial activity in coarser soils where SOM is not protected from degradation by organomineral complexes and aggregation (Hassink, 1995;Franzluebbers et al., 1996). For this reason, SOM in sandier soils is more sensitive to cultivation, and SOM losses following cultivation are more pronounced (Six et al., 2002). ...
Agricultural soils may act as a source or a sink for carbon (C) in the global C cycle. With rising atmospheric CO2 levels, C sequestration in soils may play an important role in climate change mitigation. Soil organic carbon (SOC) also contributes to key aspects of soil health and fertility, such as aggregation, water-holding capacity, microbial biomass, and nutrient mineralization. Although SOC may be calculated from estimates of soil organic matter (SOM) obtained by loss-on-ignition (LOI), factors such as sample clay concentration and combustion temperature introduce error into estimates of SOM. We explored the potential for an extensive collection of LOI values determined by the Maine Soil Testing Service from a variety of agricultural cropping systems over the last 27 years to provide insights into trends in SOM, and therefore SOC, between crop groups and over time. We evaluated furnace temperatures from 375 to 950 °C, to determine the temperature that provides the strongest correlation between SOM estimated by LOI and SOC measured instrumentally by a LECO CN Analyzer. Next, we evaluated whether including a soil texture term in a regression between SOM estimated by LOI and SOC measured instrumentally by a LECO CN Analyzer improved the ability to predict SOC. Finally, we identified trends in the SOC in Maine agricultural soils over the past 27 years based on standard soil samples received by the Maine Soil Testing Service from 1995 to 2021. On a sample set of 48 representative agricultural soils, the standard LOI temperature used by the Maine Soil Testing Service, 375 °C, correlated as well with SOC measured instrumentally as each of three higher temperatures we studied. All temperatures produced a Pearson’s correlation coefficient between 0.97 and 0.99, although the estimated concentration of SOM increased with increasing furnace temperature. Including a texture term in the regressions between SOC and SOM as estimated by LOI did not significantly impact or improve the estimation of SOC, which we found to be approximately 50% of SOM among our sample set of Maine agricultural soils. Using historical data since 1995, the SOC concentration estimated by LOI for Maine agricultural soils has increased by 23% from 1995 to 2021. SOC concentration of soils for grain, hay, and small-scale conventional vegetable and organic vegetable production increased by 24%, 15%, 23%, and 18%, respectively. SOC remained steady for corn and large-scale conventional vegetable and organic vegetable production, while trends for blueberries and apples were difficult to interpret. Among crop groups, only potato soils showed a decline in SOC since 1995. These results show that LOI with a combustion temperature of 375 °C, without the need for clay correction, can reliably estimate SOC of Maine agricultural soils. Further, our results show the value of historical data archived by the Maine Soil Testing Service to examine changes in Maine’s agricultural soils over time.
... Cette modification dans la définition des groupes fonctionnels renvoie au changement de notre perception du rôle des organismes du sol. Classiquement considérés pour leur importance dans la minéralisation des matières organiques (Marumoto et al., 1982 ;Molla et al., 1984 ;Hassink, 1995 ;Scheu et Setälä, 2002), les microorganismes (bactéries et champignons) sont aussi des acteurs majeurs de la structuration des sols (Miller et Jastrow, 2000 ;Rillig et Mumey, 2006 ;Lehmann et al., 2017 ;Costa et al., 2018). La production de substances (polymériques) extracellulaires par les microorganismes modifie la cohésion et l'hydrophobicité (Linder et al., 2005 ;Cosentino et al., 2006) des particules minérales (Chenu, 1993 ;Daynes et al., 2012), et en même temps augmente la viscosité de la solution de sol, ce qui, favorise la rétention en eau et module la conductivité hydraulique aux échelles élémentaires de structuration (Benard et al., 2019). ...
Les sols hébergent une importante biodiversité. Ils sont essentiels pour nourrir l'humanité et jouent un rôle fondamental dans les cycles biogéochimiques de la planète. Alors qu'à l'échelle du globe, un tiers des sols sont dégradés, comprendre les processus écologiques qui s'y déroulent pour mieux les préserver et les restaurer est un enjeu majeur. La diversité des organismes du sol joue un rôle central dans son fonctionnement, mais la compréhension des mécanismes expliquant le rôle de cette diversité reste limitée. Un frein majeur réside dans le fait que les travaux sur les rôles fonctionnels des organismes du sol sont généralement déconnectés de la complexité des habitats dans les sols. La modulation de l'activité et des interactions entre organismes du sol via la structure du sol reste peu explorée. Par ailleurs, l'effet des organismes sur la structure physique des sols a essentiellement été abordé par l'étude de populations monospécifiques d'organismes ingénieurs de l'écosystème. Or, cette approche ne permet pas d'étudier le rôle de la diversité interspécifique, qui nécessite de se placer à l'échelle d'assemblages plurispécifiques. A travers une revue de littérature, l'objectif de cet article est de souligner les lacunes de connaissances sur (1) le rôle de la structure physique des sols comme modulateur de l'effet de la biodiversité sur la dynamique des matières organiques, et (2) le rôle de la biodiversité et des interactions trophiques comme déterminant de la structure physique des sols. L'article propose enfin des pistes de recherche interdisciplinaires à l'interface entre écologie et physique du sol.
... Samples were pre-treated with 10% hydrofluoric acid for 24 h in order to remove paramagnetic substances and increase C concentration (Schmidt et al., 1997). Light fraction organic matter was extracted from soils by sieving and density fractionation in Ludox™ (ρ < 1.13) (Hassink, 1995). A substrate utilization test was performed according to using GN microplates with 95 different C sources (BIOLOG Inc., Hayward, California). ...
... Cette modification dans la définition des groupes fonctionnels renvoie au changement de notre perception du rôle des organismes du sol. Classiquement considérés pour leur importance dans la minéralisation des matières organiques (Marumoto et al., 1982 ;Molla et al., 1984 ;Hassink, 1995 ;Scheu et Setälä, 2002), les microorganismes (bactéries et champignons) sont aussi des acteurs majeurs de la structuration des sols (Miller et Jastrow, 2000 ;Rillig et Mumey, 2006 ;Lehmann et al., 2017 ;Costa et al., 2018). La production de substances (polymériques) extracellulaires par les microorganismes modifie la cohésion et l'hydrophobicité (Linder et al., 2005 ;Cosentino et al., 2006) des particules minérales (Chenu, 1993 ;Daynes et al., 2012), et en même temps augmente la viscosité de la solution de sol, ce qui, favorise la rétention en eau et module la conductivité hydraulique aux échelles élémentaires de structuration (Benard et al., 2019). ...
Les sols hébergent une importante biodiversité. Ils sont essentiels pour nourrir l'humanité et jouent un rôle fondamental dans les cycles biogéochimiques de la planète. Alors qu'à l'échelle du globe, un tiers des sols sont dégradés, comprendre les processus écologiques qui s'y déroulent pour mieux les préserver et les restaurer est un enjeu majeur. La diversité des organismes du sol joue un rôle central dans son fonctionnement, mais la compréhension des mécanismes expliquant le rôle de cette diversité reste limitée. Un frein majeur réside dans le fait que les travaux sur les rôles fonctionnels des organismes du sol sont généralement déconnectés de la complexité des habitats dans les sols. La modulation de l'activité et des interactions entre organismes du sol via la structure du sol reste peu explorée. Par ailleurs, l'effet des organismes sur la structure physique des sols a essentiellement été abordé par l'étude de populations monospécifiques d'organismes ingénieurs de l'écosystème. Or, cette approche ne permet pas d'étudier le rôle de la diversité interspécifique, qui nécessite de se placer à l'échelle d'assemblages plurispécifiques. A travers une revue de littérature, l'objectif de cet article est de souligner les lacunes de connaissances sur (1) le rôle de la structure physique des sols comme modulateur de l'effet de la biodiversité sur la dynamique des matières organiques, et (2) le rôle de la biodiversité et des interactions trophiques comme déterminant de la structure physique des sols. L’article propose enfin des pistes de recherche interdisciplinaires à l’interface entre écologie et physique du sol.
Comment citer cet article : Erktan A., Coq S., Blanchart E., Chevallier T., Trap J., Bernard L., Nahmani J., Hartmann C., Hedde M., Ganault P., Barot S. et Cortet J., 2022-Biodiversité et structure physique des sols : une vision spatialisée du fonctionnement des sols-Étude et Gestion des Sols, 29, 153-167 Comment télécharger cet article : https://www.afes.fr/publications/revue-etude-et-gestion-des-sols/volume-29/ Comment consulter/télécharger tous les articles de la revue EGS : https://www.afes.fr/publications/revue-etude-et-gestion-des-sols/ A.
... The impacts of tillage on soil quality indicators are well known. Generally, CT in the long-term will result in the degradation of soil quality indicators relative to NT. Conventional tillage generally decreases SOM content by disrupting soil aggregates, increasing SOM decomposition due to increasing aeration (Hassink, 1995). Long-term loss of SOM generally leads to reduced biological activity, aggregate stability, water infiltration and water storage as well as increased surface crusting and erosion (Nunes et al., 2020). ...
The improvement of soil quality in agro-ecosystems is one of the major objectives of conservation agriculture (CA) strategies. The objective of this study was to evaluate, quantify and compare the effects of two tillage practices, four crop rotation sequences, two residue management systems and their interactions on the soil quality of a Haplic Plinthosol in South Africa using the Soil Management Assessment Framework (SMAF). The evaluation was done on a CA field trial established in 2012 in the Eastern Cape Province of South Africa. The trial was laid out in a split-split-plot design with tillage: conventional tillage (CT) and no-till (NT) as main plot treatments. Sub-treatments were crop rotations: maize-fallow-maize (MFM); maize-fallow-soybean (MFS); maize-wheat-maize (MWM); maize-wheat-soybean (MWS). Residue management treatments: removal (R-) and retention (R+) were in the sub-sub plots. Soils from the CA trial were sampled at 0 – 5 and 5 – 10 cm depths after five cropping seasons (2012–2015). Thirteen soil quality indicators were determined to assess soil quality. The SMAF soil quality index (SMAF-SQI) was used as an indicator of overall soil quality. The study results demonstrated the dominance of tillage practices in significantly affecting soil biological, chemical and physical properties in the short term than crop rotation sequences and residue management systems. The soil biological indicators viz. SOC, MBC and BG activity were more sensitive to CA strategies, which confirmed their effectiveness as tools for soil quality assessments in the short-term. The study also revealed the short-term significant effects of tillage on the overall SMAF-SQI while crop rotation and residue management had no significant effects. Overall soil quality assessment using the SMAF technique provided a sound basis for distinguishing the short-term impacts of CA strategies on the function of the Haplic Plinthosol in Eastern Cape, South Africa.
... Manure adds active C to the soil which increases the ratio of labile C pool to the SOC pool, thus increasing the C pool and lability indexes, resulting in higher CMI values. Not only can manure add active C to the soil, it also adds stable C. According to Hassink (1992), manure contains a high amount of recalcitrant organic compounds that can be stored in the soil over time. Gong et al. (2009) and Lou et al. (2011) also reported that manure can increase C sequestration in soils than mineral fertilization. ...
Manure nutrient management can affect soil carbon (C) and nitrogen (N)
fractions. The objective of this study was to determine the effects of long term manure and mineral fertilizer applications on C and N fractions. This
study was conducted for 11 years under corn and soybean rotation. The
study rates included low manure (LM (4,194 kg ha−1), based on the crop’s
phosphorus (P) requirement), medium manure (MM (8,081 kg ha−1), based
on the crop’s N requirement), high manure (HM (16,162 kg ha−1), two
times the rate of MM), medium fertilizer (MF (204 kg N ha−1), recommended), high fertilizer (HF (224 kg N ha−1), high), and control. Soil
samples were collected to measure C and N fractions. HM recorded higher
particulate C (8%) at 0–10 cm and higher dissolved C (26%) at 10–20 cm
compared to LM. All manure rates had higher permanganate oxidizable C
compared to mineral fertilizer rates. Carbon management index was
higher under MM compared to the HF (17%) and MF (33%). This study
suggests that manure application (16,162 kg ha−1 rate and even 8,081 kg
ha−1 and 4,194 kg ha−1 rates in some cases) can enhance C and N pools
compared to mineral fertilizer application.
... The amount of organic C determined using 5, 10 and 20 mL of concentrated H 2 SO 4 when Active carbon was determined following Blair et al. (1995) method using 0.02 M potassium permanganate (KMnO 4 ). Particulate organic carbon (POC) was estimated following the method as described by Hassink (1995). Chloroform fumigation and incubation method as outlined by Vance et al. (1987) was followed to determine the microbial biomass carbon (MBC) in the soil samples. ...
Soil organic carbon (SOC) pools are indicators of soil productivity and sustainability and provide valuable information on the pathways of carbon sequestration in soils. We analysed organic C pools of different oxidizabilities, labile pools like particulate organic carbon, permanganate-oxidisable C, and microbial biomass carbon in soils under a long-term groundnut mono-cropping system with different management practices. Among the treatments, 50% NPK+farmyard manure (FYM) maintained a proportionately higher amount of soil carbon in passive pools (48.3%) followed by 50% NPK+ groundnut shell (GNS) (46.7%), FYM (44.7%), GNS (43.8%), 100% NPK (40.6%), 50% NPK (38.3%) and the control (32.4%). Particulate organic carbon fraction was the most sensitive fraction upon application of the amendments. Carbon stabilized from GNS and FYM sources had a skewed distribution along soil profile with a ratio of 1.2:1.0:1.4 and 1.8:1.0:1.3 at 0–15, 15–30, 30–45 cm depth, respectively. A critical carbon input of 0.32 Mg ha⁻¹y⁻¹ was needed to maintain SOC level, and the rate of conversion of crop residue C into soil organic C was about 8.1% for the present study. Combined use of chemical fertilizers and organic manure was found to be the best for enhancing SOC sequestration in groundnut mono-cropping system under hot arid eco-regions in India.
... The C/N of the POM fraction has been reported as being greater than 20 in soils under cropland, forest and grassland (Baldock et al., 2003;Bimüller et al., 2014;Hassink, 1995;Meijboom et al., 1995;Warren & Whitehead, 1988). In addition, C/N ranging from 20 to 25 are generally accepted to be the thresholds for the shift of microbial N immobilisation to N mineralisation (Nicolardot et al., 2001;Robertson & Groffman, 2015) that stabilises the C/N by balancing C and N losses and further leading to a rapid mineralisation of POM. ...
Soil organic matter is composed of fractions with different functions and reactivity. Among these, particulate organic matter (POM) is the main educt of new inputs of organic matter in soils and its chemical fate corresponds to the first stages of the SOM decomposition cascade ultimately leading to the association of organic and mineral phases. We aimed at investigating the POM molecular changes during decomposition at a sub-millimetre scale by combining direct measurements of POM elemental and molecular composition with laboratory imaging VNIR spectroscopy. For this, we set up an incubation experiment to compare the molecular composition of straw and composted green manure, materials greatly differing in their C/N ratio, during their decomposition in reconstituted topsoil or subsoil of a Luvisol, and recorded hyperspectral images at high spatial and spectral resolutions of complete soil cores at the start and end of the incubation.
Hyperspectral imaging was successfully combined with machine learning ensembles to produce a precise mapping of POM alkyl/O-N alkyl ratio and C/N, revealing the spatial heterogeneity in the composition of both straw and green manure. We found that both types of organic amendment were more degraded in the reconstituted topsoil than in subsoil after the incubation. We also measured consistent trends in molecular changes undergone by straw, with the alkyl/O-N alkyl ratio slightly increasing from 0.06 to 0.07, and C/N dropping by about 40 units. The green manure material was very heterogeneous, with no clear molecular changes detected as a result of incubation.
The imaging VNIR spectroscopy approach presented here enables high-resolution mapping of the spatial distribution of the molecular characteristics of organic particles in soil cores, and offers opportunities to disentangle the roles of POM chemistry and morphology during the first steps of the decomposition cascade of organic matter in soils.
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... On the contrary, Drinkwater et al. (1998) demonstrated that manure addition from cattle grazing in a legume-grain crop rotation showed the highest increase of SOC accumulation in the soil after 15 years compared to a low-input legume-grain crop rotation and a conventional fertilizer-based system. They suggested a greater proportion of manure-derived SOC is retained in the soil compared to plant residues, as manure is more difficult to decompose (Hassink, 1992;Paustian et al., 1992). Integrating crops and livestock allows for a better coupling of nutrient demand and availability (Liebig et al., 2012 and citations therein;Russelle et al., 2007). ...
The introduction of cover crops as fallow replacement in the traditional cereal-based cropping system of the Northern Great Plains has the potential to decrease soil erosion, increase water infiltration, reduce weed pressure and improve soil health. However, there are concerns this might come at the cost of reduced production in the subsequent wheat crop due to soil water use by the cover crops. To determine this risk, a phased 2-year rotation of 15 different cover crop mixtures and winter wheat/spring wheat was established at the Northern Agricultural Research Center near Havre, MT from 2012 to 2020, or four rotation cycles. Controls included fallow–wheat and barley–wheat sequences. Cover crops and barley were terminated early July by haying, grazing or herbicide application. Yields were significantly decreased in wheat following cover crops in 3 out of 8 years, up to maximum of 1.4 t ha ⁻¹ (or 60%) for winter wheat following cool-season cover crop mixtures. However, cover crops also unexpectedly increased following wheat yields in 2018, possibly due in part to residual fertilizer. Within cool-, mid- and warm-season cover crop groups, individual mixtures did not show significant differences impact on following grain yields. Similarly, cover crop termination methods had no impact on spring or winter wheat grain yields in any of the 8 years considered. Wheat grain protein concentration was not affected by cover crop mixtures or termination treatments but was decreased in winter wheat following barley. Differences in soil water content across cover crop groups were only evident at the beginning of the third cycle in one field, but important reductions were observed below 15 cm in the last rotation cycle. In-season rainfall explained 43 and 13% of the variability in winter and spring wheat yields, respectively, compared to 2 and 1% for the previous year cover crop biomass. Further economic analyses are required to determine if the integration of livestock is necessary to mitigate the risks associated with the introduction of cover crops in replacement of fallow in the Northern Great Plains.
... However, cover crops including annual grasses, small grains and forage legumes following grain or fiber crops could provide a source of high-quality forage for livestock Stuedemann, 2007, 2008b). In addition, manure deposited from grazing cattle has been demonstrated to increase soil organic carbon accumulation compared to a legume-grain crop rotation and a conventional fertilizer-based system, presumably due to manure taking longer to decompose than plant residue (Hassink, 1992;Paustian et al., 1992;Drinkwater et al., 1998). Therefore, an integrated crop-livestock system that utilizes livestock grazing as a mechanism to terminate cover crops is proposed to better pair nutrient demand and availability compared to other termination methods, mutually benefiting both livestock and crop producers (Russelle et al., 2007;Franzluebbers and Stuedemann, 2008a;Liebig et al., 2012). ...
Crop-livestock integration has demonstrated that cover crops can be terminated using livestock grazing with minimal negative impacts on soil health, however, provides little information on system-level approaches that mutually benefit soil health and both crop and livestock production. Therefore, the objective of this research was to examine the effects of cover crop mixtures on biomass production, quality and the potential for nitrate toxicity on a dryland wheat-cover crop rotation. This research was conducted at the Montana State University Northern Agricultural Research Center near Havre, MT (48°29′ N, −109°48′
W) from 2012 to 2019. This experiment was conducted as a randomized-complete-block design, where 29 individual species were utilized in 15 different cover crop mixtures in a wheat-cover crop rotation. Cover crop mixtures were classified into four treatment groups, including (1) cool-season species, (2) warm-season species dominant, (3) cool and warm-season species mixture (midseason), and (4) a barley (Hordeum vulgare) control. All cover crop mixtures were terminated at anthesis of cool-season cereal species to avoid volunteer cereal grains in the following wheat crop. At the time of cover crop termination, dry matter forage production was estimated and analyzed for crude protein, total digestible nutrients and nitrates as indicators of forage quality. All mixtures containing oats (Avena sativa) had greater (P ⩽ 0.03) biomass production than other mixtures within their respective treatment groups (cool- and mid-season). Forage biomass was influenced by cover crop treatment group, with the barley producing the greatest (P < 0.01) amount of forage biomass when compared to cool-, mid- and warm-season cover crop treatments. Total digestible nutrients were greater (P < 0.01) in the barley control compared to the cool- and mid-season treatment groups. Crude protein was greatest in the warm-season treatment group (P < 0.01) compared to the barley control, cool- and midseason treatment groups. The barley control produced fewer nitrates (P ⩽ 0.05) than the cool-, mid- and warm-season treatment groups; however, all cover crop mixtures produced nitrates at levels unsafe for livestock consumption at least one year of the study. The relatively high and variable nitrate levels of all cover crop mixtures across years in this study suggest that forage should be tested for nitrates before grazing. In conclusion, our research suggests that in a dryland wheat-cover crop rotation that requires early-July termination, cool-season cover crop mixtures are the most suitable forage source for livestock grazing most years.
... The soil light fractions' (LF) and soil heavy fractions' (HF) associated organic carbon (LF-SOC and HF-SOC), was determined using the density fractionation method as described by Gregorich and Ellert (1993).They are useful to identify specific carbon pools and evaluate their responses to soil management strategies which involve controlling SOC [26] and characterizing soil quality for sustainable land use [27]. Heavy fractions (HF) are more stable and contain greater processed SOC [28,29], while high-density organo-mineral fractions have lower carbon concentrations [30]. HF is a major carbon sink [31] that can lead to poor soil respiration [32]. ...
Boreal forests with high carbon sequestration capacity play a crucial role in mitigating global climate change. Addressing dynamic changes of soil organic carbon (SOC) after wildfire helps in understanding carbon cycling. The objective of this study is to investigate changes in soil organic carbon after wildfires in a boreal forest. The post-fire soil chronosequence after 3 months, 17 years, and 25 years within a boreal forest was used to examine dynamic and stable SOC after wildfire at the decadal scale. Soils in genetic horizons were sampled and analyzed for dynamic and stable SOC, including water stable aggregates (WSA), WSA associated organic carbon (WSA-SOC), soil heavy fractions (HF) associated organic carbon (HF-SOC), and soil total organic carbon (TOC). The TOC and WSA-SOC content of the A horizon was the greatest in the control site. There was no significant difference for TOC between burned and unburned deep BC horizons. The TOC for the A and B horizons at the 17-year-old site was significantly lower compared to the other sites. TOC did not recover to the pre-fire levels (control site) in any of the burned areas. The lowest WSA was found in the A and B horizons of the 3-month-old site. The WSA at the 25-year-old site was higher compared to the 17-year-old site. WSA increased with time following fire, but the recovery rate differed among different sites. The lowest concentration of WSA-SOC for the A horizon occurred at the 17-year-old site, and no significant difference was observed between B and BC horizons. The HF content for the A horizon was the greatest at the 3-month-old site. There was no significant difference in HF-SOC between B and BC horizons in all sites. TOC and stable SOC (HF and WSA) increased over time in species-dominance relay stand areas, while self-replacement stands areas showed the opposite. The results indicate that overall, the ability of soil to sequester carbon decreased after wildfire disturbances. Stable SOC accumulated more in areas where species-dominance relay succession occurred compared to the self-replacement stands. These disturbances were more pronounced for surface soil horizons. This study provides a quantitative assessment of SOC changes after wildfires that are useful for forest management and modeling forecasts of SOC stocks, especially in boreal forests.
... The organic farm soils recorded lower acidity and higher fertility levels compared to conventional farms; which could be due to application of organic fertilizers and amendments that neutralize the low soil acidity and maintain beneficial soil microorganisms that maintain soil nutrient recycling. In organic farming, the application of animals' manure and compost promote the activity and diversity of soil microbes [42] that promote nutrient cycling and enhance soil properties [43]. Organic farm soils, which had a mean pH of 5.7, higher organic carbon content compared to conventional soils with low soil pH of 4.57, consistently supported the tripartite soybean-rhizobia-AMF symbiosis leading to higher averaged values of all the tested parameters. ...
Soil amendment with beneficial microorganisms is gaining popularity among farmers to alleviate the decline of soil fertility and to increase food production and maintain environmental quality. However, farm management greatly influence soil microbial abundance and function, which overly affects crop growth and development. In this work, greenhouse experiments involving soybeans were conducted to evaluate the effects of bradyrhizobia and arbuscular mycorrhizal fungi (AMF) dual inoculation on nodulation, AMF root colonization, growth and nutrient acquisition under contrasting farming systems. The experimental treatments were AMF and/or bradyrhizobia inoculation and dual inoculation on SC squire soybean variety. The exotic AMF inoculants used were Funneliformis mosseae (BEG 12) and Rhizophagus irregularis (BEG 44) while bacteria were commercial Bradyrhizobium japonicum (USDA110) and native bradyrhizobia isolates. Experiments with soil samples from organic and conventional farms were set out using a completely randomized design with three replicates. The results demonstrated that bradyrhizobia and AMF dual inoculation consistently and significantly enhanced soybean nodule dry weight (NDW), shoot dry weight (SDW) and AMF root colonization compared with individual bradyrhizobia, AMF and non-inoculated control. Moreover, organic soil significantly (p = 0.001) increased soybean SDW, NDW and AMF root colonization compared to conventional soil. Remarkably, shoot nutrients content differed in organic and conventional farming where, shoot nitrogen, phosphorus, potassium and organic carbon were higher in organic farming than the latter. Among individual inoculants, Rhizophagus irregularis out-performed Funneliformis mosseae, while commercial Bradyrhizobium japonicum showed higher performance than native bradyrhizobia. Our results demonstrated the importance of organic farming, AMF and bradyrhizobia dual inoculation in enhancing soybean growth and nutrient acquisition. However, field trials should be assessed to determine the good performance of bradyrhizobia and AMF dual inoculation in organic farming before being popularized and adopted by farmers as a sustainable agronomical management strategy to increase soil fertility and food productivity.
... The less acidic soil in organic farms may be due to application of organic fertilizers and amendments that neutralize the low soil acidity and maintain beneficial soil microorganisms that maintain soil nutrient recycling. The application of animals' manure and compost promote the bioactivity and diversity of soil microbes (Hassink, 1995) that promote nutrient cycling rate and hence enhancing soil properties and plant productivity (Gajda et al., 2000). Organic farming system that involves the application of organic fertilizer, obliterate the use of inorganic chemical fertilizers and other agrochemicals that leads to loss of biodiversity, decline in soil fertility, pollute the environment, costly and unaffordable to most resource constrained smallholder farmers. ...
Organic farming systems are gaining popularity as agronomically and environmentally sound soil management strategies with potential to enhance soil microbial diversity and fertility, environmental quality and sustainable crop production. This work aimed at understanding the effect of organic and conventional farming on the diversity of soybean nodulating bradyrhizobia species. Field trapping of indigenous soybean Bradyrhizobium was done by planting promiscuous soybeans varieties SB16 and SC squire as well as non-promiscuous Gazelle in three organic and three conventional farms in Tharaka-Nithi County of Kenya. After 45 days of growth, 108 nodule isolates were obtained from the soybean nodules and placed into 13 groups based on their morphological characteristics. Genetic diversity was done by polymerase chain reaction (PCR) targeting 16S rDNA gene using universal primers P5-R and P3-F and sequencing was carried out using the same primer. High morphological and genetic diversity of the nodule isolates was observed in organic farms as opposed to conventional farms. There was little or no genetic differentiation between the nodule isolates from the different farms with the highest molecular variation (91.12%) being partitioned within populations as opposed to among populations (8.88%). All the isolates were identified as bradyrhizobia with close evolutionary ties with Bradyrhizobium japonicum and Bradyrhizobium yuanminense. Organic farming systems favor the proliferation of bradyrhizobia species and therefore a suitable environmentally friendly alternative for enhancing soybean production.
... The photosynthetic process generally comprises of light-induced linear electron transport and the Calvin cycle for CO 2 fixation. Linear electron transport employs photosystem II (PSII) and photosystem I (PSI) to produce ATP and NADPH, two important chemical compounds used to fuel the Calvin cycle for CO 2 fixation [4]. The majority of previous research applies chlorophyll content, photosynthetic rate, leaf area index and other indicators to determine the effects of different planting densities on the photosynthetic characteristics of maize. ...
The mutual shading among individual field-grown maize plants resulting from high planting density inevitably reduces leaf photosynthesis, while regulating the photosynthetic transport chain has a strong impact on photosynthesis. However, the effect of high planting density on the photosynthetic electron transport chain in maize currently remains unclear. In this study, we simultaneously measured prompt chlorophyll a fluorescence (PF), modulated 820 nm reflection (MR) and delayed chlorophyll a fluorescence (DF) in order to investigate the effect of high planting density on the photosynthetic electron transport chain in two maize hybrids widely grown in China. PF transients demonstrated a gradual reduction in their signal amplitude with increasing planting density. In addition, high planting density induced positive J-step and G-bands of the PF transients, reduced the values of PF parameters PIABS, RC/CSO, TRO/ABS, ETO/TRO and REO/ETO, and enhanced ABS/RC and N. MR kinetics showed an increase of their lowest point with increasing high planting density, and thus the values of MR parameters VPSI and VPSII-PSI were reduced. The shapes of DF induction and decay curves were changed by high planting density. In addition, high planting density reduced the values of DF parameters I1, I2, L1 and L2, and enhanced I2/I1. These results suggested that high planting density caused harm on multiple components of maize photosynthetic electron transport chain, including an inactivation of PSII RCs, a blocked electron transfer between QA and QB, a reduction in PSI oxidation and re-reduction activities, and an impaired PSI acceptor side. Moreover, a comparison between PSII and PSI activities demonstrated the greater effect of plant density on the former.
... The LFOC was labile fractions that represent an intermediate organic carbon pool between humified organic matter and undecomposed residues (Janzen et al., 1992). The HFOC was a stable carbon pool that has slow decomposition rate and transformation rate Hassink, 1995;John et al., 2005). Oades (1984) and Elliott (1986) found that the roots and the fungal hyphae in LFOC can promote the formation of aggregates directly. ...
Aggregate disintegration is a critical process in soil splash erosion. However, the effect of soil organic carbon (SOC) and its fractions on soil aggregates disintegration is still not clear. In this study, five soils with similar clay contents and different contents of SOC have been used. The effects of slaking and mechanical striking on splash erosion were distinguished by using deionized water and 95% ethanol as raindrops. The simulated rainfall experiments were carried out in four heights (0.5, 1.0, 1.5, and 2.0 m). The result indicated that the soil aggregate stability increased with the increases of SOC and light fraction organic carbon (LFOC). The relative slaking and the mechanical striking index increased with the decreases of SOC and LFOC. The reduction of macroaggregates in eroded soil gradually decreased with the increase of SOC and LFOC, especially in alcohol test. The amount of macroaggregates (>0.25mm) in deionized water tests were significantly less than that in alcohol tests under the same rainfall heights. The contribution of slaking to splash erosion increased with the decrease of heavy fractions organic carbon (HFOC). The contribution of mechanical striking was dominant when the rainfall kinetic energy increased to a range of threshold between 9 J m‐2 mm‐1 and 12 m‐2 mm‐1. This study could provide the scientific basis for deeply understanding the mechanism of soil aggregates disintegration and splash erosion.
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... A recently developed method for fractionation of soil samples in suspended silica solutions of various physical densities, in combination with sieving (Meijboom et al. , 1995;Hassink, 1995) has a similar objective. Fresh plant material has a physical density of about 1 mg cm· 3 ; if organic material gets more and more associated with mineral soil particles (e.g. by faunal activity) it enters heavier fractions. ...
... Furthermore, the assimilation of organic N by microorganisms is critical to determine the pool size of soil N . In particular, the activity and biomass of microorganisms indigenous to soils can immediately affect organic N metabolism (Hassink, 1995;Mcmillan et al., 2007;Verhoef and Brussaard, 1990). Conservation tillage soils increased the stability and diversity of the microbial community structure, which might have caused an increase in the soil N pool. ...
Conservation tillage has been recommended as one of the effective soil management practices for mitigating the negative environmental effects of synthetic ammonia application and achieving cleaner agricultural production. However, information about how long-term conservation tillage affects agroecosystem nitrogen balance in dryland winter wheat-summer maize cropping is limited. Based on a long-term (>9 yr) field tillage experiment and in-situ observation, we assessed the effects of different tillage practices, including two conservation tillage methods (i.e., chisel plough tillage (CPT) and zero tillage (ZT)) and conventional ploughing tillage (PT) as the control, on soil nitrogen balance and crop productivity in the 2016–2017 and 2017–2018 growing seasons. Each tillage practice was exposed to a local widely adopted N application rate (240 kg ha⁻¹ yr⁻¹) in both seasons. Our results indicated that, compared with PT, CPT and ZT significantly (P < 0.05) reduced N2O emissions by 39.7 % (2.8 kg N ha⁻¹ yr⁻¹) and 55.3% (3.9 kg N ha⁻¹ yr⁻¹), and N leaching by 52.3% (11.8 kg N ha⁻¹ yr ⁻¹) and 147.7 % (33.3 kg N ha⁻¹ yr⁻¹) across the two growing seasons, respectively. CPT significantly enhanced crop aboveground N uptake by 4.0%, and eventually led to an increase in the annual crop yield by 5.9∼8.1% (0.8∼1.2 t ha⁻¹ yr⁻¹). Although CPT and ZT enhanced NH3 volatilization by 46.7% (14.6 kg N ha⁻¹ yr⁻¹) and 84.3% (26.3 kg N ha⁻¹ yr⁻¹), the total N losses under CPT and ZT were decreased on an average by 7.4% and 22.4%, respectively. Overall, CPT and ZT significantly increased the accumulation of soil total nitrogen in the 0–100 cm layer by 34.8 and 54.1 kg N ha⁻¹ yr⁻¹, respectively. Taking N inputs and outputs together, CPT achieved a lower N surplus mainly due to increased crop N harvest and reduced N losses including gaseous emissions and hydrological leaching. Our findings suggest that long-term chisel plough tillage in dryland agroecosystems could serve as a promising soil management practice in increasing crop productivity and maintaining sustainability by enhancing N removal from crop biomass and decreasing N losses via N2O emission and nitrate-N leaching.
... Microbial biomass carbon (MBC) can be determined by measuring the flush of carbon released from soil, in response to chloroform fumigation, and it corresponds to the entirety of microorganisms therein [2]. Soil microbial biomass can immobilize and mineralize nutrients [3,4]. Although MBC corresponds to only 1-3% [5] of soil organic carbon (SOC), microbes play a central role in aggregate formation during soil structural development [6]. ...
Soil microbes are key to nutrient cycling and soil formation, yet the impact of soil properties on microbe biomass remains unclear. Using 240 soil cores of 0–15 cm depth, taken at random points across six cattle-grazed pastures on an undulating landscape, we evaluated the biomass of microbes in soil as affected by naturally occurring variation in soil organic carbon (SOC), clay content, and local topography. The study pastures varied in historic land-use for crops or forage seeding. SOC was found to be greater in topographically low areas. In contrast, clay content was not related to topography, and clay deposition possibly varies with glaciation legacy. Microbial biomass carbon (MBC) was correlated positively with SOC, increasing from 700 mg kg−1 MBC at 25 g kg−1 SOC to 2240 mg kg−1 MBC at 90 g kg−1 SOC. Most likely, SOC promotes MBC through the release of water-soluble organic carbon. However, the response of MBC to clay content was negative, decreasing from 1340 mg kg−1 MBC at 5% clay to 880 mg kg−1 MBC at 30% clay. Small voids in association with clay particles likely restrict the access of microbes to SOC. The relationship between SOC and MBC illustrates the important role of SOC for soil function, in terms of nutrient availability and development of soil structure via the contribution of microbes. Lastly, there was considerable spatial variability in MBC across the 65 ha site, highlighting the importance of land-use histories and gradients in environmental variables, to determine the biomass of microbes in soil.
... There was a positive relation between cPOC and fPOC with SOC (R 2 =0.37 & 0.81) (Fig. 5.7). Similar results were also reported by Hassink (1995) and Rudrappa et al. (2005). ...
Improving soil organic carbon (SOC) stocks is of a vital important for enhancing soil productivity of different land use systems, particularly, in arid and semi-arid regions of the country. The study was carried out to evaluate the SOC fractions and their relationships with soil properties as influenced by different cropping systems and management practices. Thirteen sites under different land use systems were selected for soil sampling from the States of Rajasthan and Haryana. Soil samples were analysed for various soil properties and SOC fractions, and their relationships were established. The soils at different sampling sites were alkaline in reaction and non-saline. Higher bulk density was observed in coarse textured fallow soils and in soils under rice-wheat system. Significantly lower bulk density observed under plantation forest and agro forestry than field crops was attributed to greater inputs of plant biomass and/or application of manures and fertilizers. Among different cropping systems, sugarcane and rice-wheat systems found to have higher SOC content due to their potential for higher biomass production. At all sited, the SOC content found to be decreased with depth due to reduced amount of organic matter. Aggregation, CEC and nutrients status of soils were higher under agro-forestry, sugarcane, horticulture and cotton-wheat than other systems due to higher SOC status and clay contents. Similarly, the oxidizable fractions of carbon (very labile, labile, less labile and non-labile) were also significantly higher under plantation forest, sugarcane, agro-forestry and rice-wheat land use systems because of higher biomass input. Upon differentiating the SOC into active (AC) and passive carbon (PC), the AC was found variable under different cropping systems, and significantly higher under plantation forest, sugarcane and agro-forestry land use systems. Therefore, the AC and their proportion to total SOC could be use as sensitive indicator of soil health. As per physical classification of SOC, coarse particulate organic carbon (POC) was significantly higher under plantation forest, horticulture, agro-forestry and mung bean-mustard land use systems due to heavier texture of soil and/or introduction of legume in crop rotation. For the surface layers, the largest differences in POC content were observed for the aggregate associated POC, which was apparent in soils with more effective native vegetation. Significantly higher microbial biomass carbon (MBC)content under plantation forest, horticulture and agro-forestry land use systems was attributed to the production of high quantity of litter fall (substrate) for microbial decomposition every year. Among the different cropping systems, sugarcane and rice-wheat systems had significantly higher MBC content probably due to higher accumulation of SOC and relatively higher inputs of manures and fertilizers included in management practices. Significantly higher SOC stock under plantation forest and agro-forestry systems obtained were attributed to relatively more litter biomass production, stubble and rhizo deposits and slower decomposition of soil organic matter in the undisturbed soil. Variation in texture of soils and management practices in different land use systems were found responsible for organic carbon storage in soils. Use of poor quality irrigation water in sugarcane, rice-wheat and guar-wheat cropping systems adversely affected the SOC pools and soil properties. The Carbon Management Index found effective in assessing C sequestration potential of soils under different cropping systems. Very labile carbon was significantly correlated with SOC (r = 0.98), CEC (r = 0.82), aggregation (r = 0.63) available N (r = 0.94), available P (r = 0.81), available K (r = 0.64).The higher value of correlation coefficient between labile carbon pools with total SOC indicated that these pools were most affected by changes in land use and management practices. The MBC was correlated with total SOC (r = 0.85), coarse (r = 0.85) and fine (r = 0.91) POC, AC (r = 0.85) and PC (r = 0.85). There was a dynamic relationship between different pools of SOC and their relative proportion was greatly influenced by land use systems. It was concluded that the changes in labile fraction of SOC may be considered as a sensitive indicator for assessing the quality of SOC being added in soils under different land use systems in arid and semi-arid regions of North-Western India.
... The method as described by Cambaredella and Elliott (1992) and Hassink (1995) was used to estimate particulate organic C (POC). A 50 g portion of the soil was dispersed with 150 ml of 0.5% sodium hexametaphosphate solution and shaken for 15 h on a reciprocal shaker. ...
A study was conducted to assess the impact of different land use systems on soil organic carbon (SOC), its fractions and soil organic carbon stocks under different land use systems in a mixed watershed in the submontane region of north-west India. Soil samples were collected up to a depth of 120 cm from three locations each from maize-wheat, agro-horticulture and agroforestry (3 and 6-year plantation) land use systems. The results revealed that the surface soils (0–15 cm) under agroforestry had significantly higher SOC (5.3 mg g− 1) than in soils under other cropping systems and varied from 4.3 to 5.3 mg g− 1. The labile carbon (LC), aggregate associated carbon (AAC), particulate organic carbon (POC) and mineralizable carbon (MC) were also significantly higher in surface soils under agroforestry 6-year plantation than other three cropping systems and thereafter exhibited significantly lower content of SOC and its fractions in each of the depth as compared to the surface soil in all the cropping systems except maize-wheat system where LC increased significantly in the second depth and decreased gradually in the subsequent lower depths. The proportion of these fractions in relation to the soil organic carbon was lowest in soils under maize-wheat (10–70%) than the tree-based cropping systems (20–100%). The typical decrease of SOC content in the 3rd depth (30–60 cm) was the sharpest and thereafter it stabilized in lower depths in maize-wheat system. The SOC stock followed the trend: agroforestry 6-year (38 Mg ha− 1) > agroforestry 3-year (30.5 Mg ha− 1) > agrohorticulture or maize-wheat system (27.5 Mg ha− 1). Up to 33% lower SOC stocks were recorded in maize-wheat or agrohorticulture cropping systems than under the agroforestry land use system, thereby suggesting that conversion of forest land to agroecosystems can contribute to losses of up to 10.5 Mg ha− 1 SOC over time. Overall conclusion from this investigation is that SOC levels are strongly influenced by the prevailing land use systems.
... Nevertheless, the light fraction also correlates well with the rate of N mineralization [47]. However, heavy fraction C has low C concentrations and is more stable at a high density [48,49]. Heavy fraction C can be a major problem for soil fertility because it contains mineralizable C [50]. ...
Fulvic acids (FAs) improve the structure and fertility of soils with varying textures and also play a crucial role in increasing crop production. The pot experiment was carried out using wheat grown on three soils with a silty clay, sandy loam, and clay loam texture, respectively. The soils were treated with FAs derived from plant and mineral materials. Plant-derived solid (PSFA), mineral-derived liquid (NLFA), and plant-derived liquid (PLFA) were applied at a rate of 2.5, 5, and 5 g kg −1 and control applied at 0 g kg −1. The results showed that in treated soils, the heavy fraction C was higher by 10%-60%, and the light fraction C increased by 30%-60%. Similarly, the available N content significantly increased in treated soils by 30%-70% and the available K content increased by 20%-45%, while P content significantly increased by 80%-90% in Aridisols and Vertisols and decreased by 60%-70% in Mollisols. In contrast, for P, the organic-inorganic compounds were greater in Aridisols and Vertisols and lower in Mollisols. However, organic-inorganic composites decreased in Vertisols relative to the other two soils. Further results showed that PSFA and NLFA accelerated the plant growth parameters in Mollisols and Aridisols, respectively. Our study demonstrates that the application of PSFA and NLFA had a positive effect on the physical and chemical properties and plant growth characteristics of Mollisol and Vertisol soils. Moreover, the application of solid-state FA yields better results in Mollisols. However, liquid FA increases the nutrient availability and the effects on the chemical, biological, and physical properties of Aridisol and Vertisol soils.
Revegetation is an effective measure to enhance soil organic carbon (OC) and nitrogen (N) storage in drylands, but the underlying processes remain poorly understood. Based on density fractionation, the free light fraction (fLF), the occluded light fraction (oLF), and a heavy fraction (HF) were extracted from a chronosequence of revegetated sites aged 10, 22, 34, 48, and 65 years. A mobile sand dune (MSD) was used as the reference site (aged 0 years). The OC and N contents of different fractions and the bulk soils were determined to evaluate the impacts of revegetation and clarify post‐revegetation stabilization mechanisms for the OC and N. The results showed that the dry mass of fLF and oLF in established shrublands were 17.16–31.30 and 17.68–44.87 times greater than those in the MSD, respectively, while the amount of HF decreased by 1.09%–2.51% in 65 years. The contents and stocks of OC and N and C:N ratio in each fraction significantly increased over time but decreased with soil depth, and these three variables decreased sequentially from fLF to oLF to HF. The OC and N contents and their ratios in each fraction were positively and linearly correlated with their corresponding values in the bulk soil. The OC and N percentages contained in the fLF and oLF increased significantly, but those in the HF decreased with increasing site age. Despite this, more than 55.08% of OC and 80.59% of N were remained in the HF across all the sites, indicating that the enhancement of OC and N stocks in SOM following revegetation were mainly derived from an increase in OC and N in protected fractions. Biological and physicochemical factors including microbial biomass C and N, the availability of N, P, and K, bulk density, and clay and silt contents, were the key factors regulating the OC and N dynamics in the density fractions. The initial OC and N accumulation after revegetation occurs mainly in the HF, while vegetation development shifts the OC and N from stable to labile pools. The OC and N accumulation in revegetated soils is attributed to the changes in both the LF and HF whereas OC and N in the light fraction become increasingly important over time. Stabilization by forming aggregates and mineral associations may dominate the long‐term OC and N sequestration in restored ecosystems.
Abstract
To understand the soil health under continuous cultivation after using organic and chemical inputs, a survey was conducted under Uttarakhand, Navdanya farm areas, where farmers were selected who were practicing both chemical and organic inputs under different crops at least more than 5 years. The effect of most important crops growing under Uttarakhand i.e. wheat, potato, garlic, mustard, chick pea, chilli, and pumpkin was taken into consideration. The results clearly suggested that a significant decline in most important soil enzyme activities like dehydrogenase, esterase, acid and alkaline phosphatase under chemical farming as compared to organic farming. The microbial population especially fungi, bacteria, actinomycetes, azotobacter and Nitrosomonas was significantly higher under organic farming areas than chemical farming. The results clearly showed that organic farming has a great role to maintain excellent microbial and enzyme activities resulted better soil health status.
Keywords: soil health, organic input, chemical input, conventional farming, enzyme.
Organic manure application has its significant impact on the soil health. Low organic matter in tropical soils is a major factor contributing to their poor productivity. Soil properties have been continuously influenced by the management practices and land uses, in which latter one has been, identified as profound influence on soil properties especially on soil organic carbon. A thirteen year experiment on soybean based cropping system in a vertisol of central india under organic farming was used for this investigation An investigation was carried out on “Soil organic carbon dynamics under long-term nutrient management in soybean based cropping system” at the Indian Institute of Soil Science, Bhopal on an on-going research project on organic farming. The effect of organic, integrated and inorganic nutrient management was assessed in three cropping systems viz. soybean (JS 335)-wheat (Malwa Shakti), soybean-mustard (Pusa Bold) and soybean-gram (JG 130) on aggregate size fractions, carbon content in aggregate as well as soil organic carbon pools dynamics on a split plot experimental design with three replications. The study relevant to dynamics of soil organic carbon pools revealed higher content of soil organic carbon, labile carbon, water soluble carbon, SMBC as well as dehydrogenase activity that varied between 1.04 and 0.86 percent; 440 and 538 mg kg-1, 52.97 and 70.43; 288 and 375 mg kg-1, 88 and 137 µg TPF g-1 soil d-1, respectively in surface 0-15 cm soil under organic nutrient management.
The objective of the study was to elucidate the relationship between soil management and carbon (C) stocks, and to identify the factors that intervene in the processes that favor C sequestration. The study was carried out on a farm in the Argentinean semiarid pampas with four land management practices (2019-2021): natural grassland (NG), crop-pasture rotation (RO), soybean monoculture (S-S) and with cover crop (S-CC). Aerial and root biomass were quantified at cover crop termination and soybean flowering. In addition, residues on soil surface were determined two times a year. In all cases, C and N contents were quantified. On composite soil samples, soil organic C (SOC), particulate C (POC), microbial biomass C and N (MBC, MBN), and soluble C and N were determined at 0-0.1 m depth. Results showed that NG had the highest and the most stable aboveground (3807.1 kg residue-C ha-1) and belowground inputs between years (4965.8 kg root-C ha-1). Similar results were observed in RO treatment during the first year (4221.0 kg root-C ha-1) diminishing by 67% after plowing for the annual crop in the second year reaching similar root-C values than S-CC and S-S (721.7 kg ha-1). S-S presented the lowest aboveground (49%) and belowground inputs (77%) compared to NG. Cover crops (S-CC) contributed with 31% and 14% of extra residue-C and root-C, respectively, compared to S-S. MBC showed a non-linear response with increases in root-C, reaching maximum carrying capacity of 110.6 ± 4.3 kg MBC ha-1 with root-C inputs ≥ 2200 kg ha-1. Our results showed significant relationships between root-C and POC and SOC, while no relationships were found for aboveground residues. Increases in soluble N explained 86% of SOC variability. Both RO and S-CC reached the "4 per Mille" goal with an average annual SOC storage rate (ΔC) of 0.24 and 0.16 Mg ha-1 y-1 , respectively, while S-S had SOC losses of 0.04 Mg ha-1 yr-1 .
In the modern era, urban freshwater bodies play a significant role in global carbon (C) budgeting, therefore, impacting climate change under rising global mean temperature. However, the trend, magnitude, and drivers of Greenhouse gas (GHG) emissions in these urban freshwater bodies of China remain uncertain. Present study investigated temporal changes in GHG emissions in urban water bodies, including artificial lakes, reservoirs, aquaculture ponds, and rivers, within a year in Nanjing city in the areas of the Yangtze River delta of China. In addition, meteorological and hydrochemical parameters were measured to elucidate the key drivers of GHG emissions. The results showed that the average annual flux of carbon dioxide (CO2) and methane (CH4) in aquaculture ponds was estimated to be 1355.6 mg CO2 m‐2 day‐1 and 116.6 mg CH4 m‐2 day‐1, followed by that of artificial lakes were 1172.2 mg CO2 m‐2 day‐1 and 44.1 mg CH4 m‐2 day‐1, rivers reached 775.9 mg CO2 m‐2 day‐1 and 23.9 mg CH4 m‐2 day‐1 and reservoirs were 170.1 mg CO2 m‐2 day‐1 and 7.2 mg CH4 m‐2 day‐1, respectively. The results further suggest that although artificial lakes and aquaculture ponds occupied only 23% of the cumulative area under lakes and ponds in the Yangtze River delta, contribute approximately 43%, about 27.5 Gg C, of total fluxes. Furthermore, high concentrations of dissolved organic carbon (DOC) and low dissolved oxygen (DO) coincided with the high GHG emissions. The study suggests that DO, DOC, temperature, and wind speed are the key factors impacting the potential of GHG emissions in urban freshwater ecosystems. Strategic mitigation measures in the vicinity of the urban freshwater bodies could efficiently reduce carbon emissions in the future.
Crop residue incorporation as general cropland management practice notably improves soil organic carbon (SOC) stock. However, the effects of crop residue input rate incorporation on SOC stability remain uncertain. Here, we conducted a 12-year field experiment to evaluate the long-term effects of crop residue incorporation on SOC stocks, stabilities, and their abiotic and biotic controls in subtropical calcareous soil under a maize-wheat rotation. Four experimental treatments, including no crop residue incorporation (control), 30% of harvested crop residue incorporation (CR30), 50% of harvested crop residue incorporation (CR50), and 100% of harvested crop residue incorporation (CR100), were implemented. Our results showed that the CR100 treatment significantly increased SOC stock by 25.6%, as compared with the control. Soil dissolved organic carbon (DOC) and particulate organic carbon (POC) contents for CR100 treatment were also significantly greater than those for the control, while no significant difference in soil microbial biomass carbon (MBC) content across different experimental treatments were found. POC content for CR50 was significantly lower than the other treatments. It is noteworthy that the relative abundance of Thaumarchaeota related to microbial SOC decompositions for CR100 was significantly lower than other experimental treatments. The temperature sensitivity (Q10) of SOC mineralization for CR50 treatment was significantly higher, as compared with other treatments. Nevertheless, the partial least squares path modeling analysis (PLS-PM) illustrated that soil aggregation and DOC content were the main regulators of Q10 for SOC mineralization thereby regulating the stability of SOC. Our results suggest that the practice of 100% of harvested crop residue incorporation is effective to increase the magnitude and the stability of SOC stocks in subtropical calcareous agricultural soils, in particular on a long-term basis.
In recent time, concerns are rising related to climate change, and mitigation measure such as soil has caught attention for the research community as a reservoir for storage of atmospheric carbon dioxide (CO2). The soil organic carbon (SOC) stabilization mechanisms have recently received a lot of focus because of its significance in governing the global carbon (C) cycle. The aim of the present chapter lies in reviewing the existing understanding on soil organic matter (SOM) dynamics with particular mention toward the contribution of clay mineralogy in retention as well as the stabilization of organic C in the soil. Thorough knowledge of the SOC stabilization mechanisms would assist in implementing optimal management practices for storage of SOC, enhancing the soil structure, and lastly mitigating the emissions of greenhouse gases. In this chapter, the relationships existing between SOC dynamics with its sources as well as sinks, aspects controlling SOC sequestration, and several mechanisms involved in the process of SOC stabilization are discussed. The studies related to soil examination, management, and environmental factors that affect the SOC stabilization with a particular mention to the clay mineralogy are provided.
The global greenhouse gas emission rapidly rises every year, and its impact on climate change is evident with no doubt. Soil being a major sink of atmospheric carbon dioxide (CO2) has attracted much attention to researchers studying ways it can be well managed to mitigate the issue of climate change. Several studies are undertaken with the aim to reveal the mechanisms through which soil minerals interact and hence adsorb organic carbon (OC). As a result, it is well established that soil plays a significant role in the control of the global carbon cycle through sorption of OC and stabilizing it. However, when soil is not well-managed, mineralization causes the release of OC, resulting in an increase of the CO2 to the atmosphere. This calls for the need to understand the mechanisms through which OC-soil mineral associations can be maintained.
Particulate organic matter (POM) plays important role in soil organic carbon (SOC) retention and soil aggregation. This paper assesses how quality (chemical composition) of four different‐quality organic residues applied annually to a tropical sandy loam soil for 10 years has affected POM pools and the development of soil aggregates. Water‐stable aggregate size distribution (>2, 0·25–2, 0·106–0·25 mm) was determined through wet sieving. Density fractionation was employed to determine POM (light—LF, and heavy—HF fractions, 0·05–1 mm). Tamarind leaf litter showed the highest SOC (<1 mm) accumulation, while rice straw showed the lowest. LF‐C contents had positive correlations with high contents of C and recalcitrant constituents, (i.e. lignin and polyphenols) of the residues. Dipterocarp, a resistant residue, showed the highest LF‐C, followed by the intermediate residues, tamarind, and groundnut, whereas HF was higher in groundnut and tamarind than dipterocarp residues. Rice straw had the lowest LF‐ and HF‐C contents. Tamarind had the highest quantity (51 per cent) of small macroaggregates (0·25–2 mm), while dipterocarp had the most (2·1 per cent) large macroaggregates (>2 mm). Rice straw had the lowest quantities of both macroaggregates. Similar to small‐sized HF (0·05–0·25 mm), small macroaggregates had positive correlation with N and negative correlation with C/N ratios, while large macroaggregates had positive correlations with C and recalcitrant constituents of the residues. Tamarind, with intermediate contents of N and recalcitrant compounds, appears to best promote small macroaggregate formation. Carbon stabilized in small macroaggregates accounted for the tamarind treatment showing the largest SOC accumulation. Copyright © 2010 John Wiley & Sons, Ltd.
The theoretical and experimental basis for current physical methods for fractioning soil in order to study organic matter and the products of its interaction with the mineral phase are examined. The method described, based on a combination of particle-size and densimetric fractionation, makes it possible to isolate five fractions that differ clearly in the nature of the organic and mineral components, their proportions and bond types. This method separates the humus fractions which are closely related to field management practices. -Journal summary
The objective of the study was to determine the influence of agronomic variables on soil light-fraction (LF) organic matter content. Soils from three long-term crop rotation studies in Saskatchewan, Canada, were analyzed for LF content and composition. The experiments, established at Indian Head, Melfort and Scott included wheatbased rotations. Within each site, the LF content was generally highest in treatments with continuous cropping or perennial forages and lowest in those with a high frequency of summer fallow. Fertilizer application generally favored LF accumulation. Differences in LF content were attributed to variable residue inputs and rates of substrate decomposition. The LF content is a sensitive indicator of the effects of cropping but, because of its transient nature, probably reflects primarily short-term effects. -from Authors
Soils from grass-arable cropping sequences and from an experiment where grassland had been treated with slurry were dispersed by shaking as a soil-water mixture, followed by ultrasonic treatment. Organo-mineral particle size fractions were separated by sieving and by sedimentation.
Generally, concentration of C and N in the fractions decreased with increasing particle size. However, when expressed as weight of C per fraction maximum contents were in the 2–10 μm range. With N, maximum contents occurred about 2 μm. Largest differences in C and N contents between soils were found in the 0·2–20 μm size range.
Identification of the source of the materials in the various fractions was attempted by interpretation of the C/N ratios, but was generally inconclusive.
A new method for the determination of biomass in soil is described. Soil is fumigated with CHCl3 vapour, the CHCl3 removed and the soil then incubated. The biomass is calculated from the difference between the amounts of CO2 evolved during incubation by fumigated and unfumigated soil. The method was tested on a set of nine soils from long-term field experiments. The amounts of biomass C ha−1 in the top 23 cm of soil from plots on the Broadbalk continuous wheat experiment were 530 kg (unmanured plot), 590 (plot receiving inorganic fertilizers) and 1160 (plot receiving farmyard manure). Soils that had been fallowed for 1 year contained less biomass than soils carrying a crop. A calcareous woodland soil contained 1960 kg biomass C ha−1, and an unmanured soil under permanent grass 2020. The arable soils contained about 2% of their organic C in the biomass; uncultivated soils a little more—about 3%.
A method is described for the rapid and objective estimation of the amount of carbon in the living, non-resting microbial biomass of soils. The method, which is based on the initial respiratory response of microbial populations to amendment with an excess of a carbon and energy source, was quantified using an expanded version of Jenkinson's technique.The simultaneous application of the two methods to 50 soil samples showed a highly significant correlation (r = 0.96) between both. From this correlation it could be deduced that at 22°C, a substrate-induced maximal respiratory rate of 1 ml CO2· h−1 corresponds to c. 40 mg microbial biomass C. Evidence supporting these results was obtained from pure culture studies. The various soil types investigated were collected from agricultural as well as forest sites and they contained between 15 and 240 mg microbial C·100g dry soil−1. The respiratory method provides reproducible estimates of biomass size within 1–3 h after soil amendment. It can be combined without difficulty with a selective inhibition method for determination of bacterial and fungal contributions to soil metabolism.