Article

Carbon dioxide and oxygen exchange at the soil-atmosphere boundary as affected by various mulch materials

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Abstract

Mulching is a common soil management technique used in agricultural, nursery, and landscape settings. Despite multiple benefits, such as reducing weeds and evaporation, some mulches can also hinder gas exchange across the soil-atmosphere interface, and thus may have negative impacts on plant growth. The objective of this study was to determine to what degree commonly used landscape mulches will affect carbon dioxide and oxygen concentrations in the root zone and gas exchange across the soil-atmosphere interface in a controlled greenhouse environment. We used mesocosms filled with a soil-compost mix and covered the surface with different mulches. The experimental treatments included no mulch (control), arborist wood chip mulch, cardboard mulch, landscape fabric mulch, and polyethylene film mulch. The flux of CO2 across the soil-atmosphere boundary was measured with the dynamic closed chamber method. Concentrations of CO2 and O2 were measured in the mesocosms at two depths (6.5 and 13.5 cm) for a total of 16 days after covering the mesocosms with the mulches. Diffusion coefficients of CO2 through mulch materials were of the order of>10−3, 10−4, 10−5, and 10−6 cm2 s−1 for wood chips, cardboard, landscape fabric, and polyethylene film, respectively. Despite the different diffusion coefficients of the different mulches, CO2 and O2 concentrations in the soil under the various mulches were not significantly different as compared to the control, except for the polyethylene treatment. The orders of magnitude differences in diffusion coefficients among the mulch materials, however, could negatively impact a diverse soil environment such as those found in biologically rich landscapes with higher oxygen demands. Among the mulches tested, wood chips are a preferred method of mulching in terms of providing best gas permeability, particularly in landscape conditions.

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... Plastic film mulching (PFM) can effectively reduce field water consumption (Shahzad et al., 2019), increase soil temperature (Lee et al., 2020;Hwang et al., 2019), and shorten the growing period of crops (Steinmetz et al., 2016). Since 1970s, this technology has been widely applied in agriculture worldwide (Sintim et al., 2018). ...
... It is extremely useful to decrease soil evaporation (E) for the improvement of water use efficiency (WUE) (Wagle et al., 2020), as there are clear differences in E in various ecosystems, especially with different film mulching conditions. Different types of films have different water vapor permeability, disintegration rate, and coverage degree, which caused the marked differences in water vapor exchange between the soil surface and atmosphere (Briassoulis and Giannoulis, 2018;Shahzad et al., 2019). For example, with more water vapor permeability and more E, E under biodegradable film mulching (BFM) was 33.8% higher than with plastic film mulching (PFM) after disintegrating for the biodegradable film . ...
... Moreover, the leaf contact surface to absorb solar radiation increases quickly, so T is further increased causing SWCs in the corresponding root zone to decrease. Previously published research has indicated that PFM can effectively increase LAI and increase T (Shahzad et al., 2019;Sintim et al., 2018;Lamptey et al., 2020). A similar result was found in our study showing that T in the mulched field (BFM and PFM) was 23.0% higher than in NFM, whereas T under BFM was 6.6% lower than with PFM. ...
Article
Biodegradable film mulching (BFM) in various crops is a good alternative to plastic film mulching (PFM). However, the difference in field water consumption between BFM and PFM has not been fully investigated. A four-year experiment with an improved evapotranspiration (ET) model (BSW) was performed to systematically evaluate and compare the effects of BFM, PFM, and no film mulching (NFM) on ET dynamics. The experiments were done in the Hetao Irrigation District of China at the Baleng experimental station (B station) with sandy soil in 2016-2017 and the Jiuzhuang experimental station (J station) with sandy loam soil in 2018-2019. The results of multi-year verification illustrated that the model accuracy was well-supported during 2016-2019 with mean absolute error (MAE) of 9.0%-16.9% and 13.1%-19.1% for ET and evaporation (E), respectively. The average cumulative ET (CET) under FM (i.e., BFM and PFM) was 443.5 mm each year and decreased by 13.4% compared to NFM. However, there was an obvious difference in CET during the different hydrological years, especially in the early crop growth stages. In the wet years (2016 and 2018), the average CET under FM increased by 6.2%-7.0% compared to NFM but decreased by 7.1%-11.8% in the dry years (2017 and 2019). The transpiration (T) difference between FM and NFM primarily appeared in the early crop growth stages, and T/ET under FM was significantly higher than with NFM by 46.9%-50.2%. An obvious E difference between BFM and PFM was observed in the later crop growing stages due to a greater area of the disintegrated biodegradable film. Additionally , crop yield under PFM and BFM increased by 35.4% and 28.3% compared with NFM, respectively, and water use efficiency (WUE) increased by 47.1% and 35.8%, respectively. Thus, biodegradable film is recommended to replace plastic film to effectively promote the development of sustainable agriculture.
... Soil O 2 is obtained directly from the atmosphere mainly by diffusion (Li et al., 2016a). However, mulching materials can interfere with the gas exchange at the soil-atmosphere interface and change soil temperature, which affects soil nutrient transformation (Shahzad et al., 2019). In the present study, mulching significantly increased SOM content compared with the conditions in the CK treatment; the high organic material input associated with the mulching treatments could be responsible for the rapid SOM accumulation, the decomposition of the rice husks could bring a high amount of labile organic C into the soil (Agegnehu et al., 2016;Jiang et al., 2006). ...
... The TA1 and TA2 treatments showed higher nutrient content (SOM, TN, NH 4 + -N, NO 3 − -N, AP) than the T1 treatment, which could be explained in three ways. First, the superior aeration conditions in the TA1 and TA2 treatments promoted the transformation of organic materials, resulting in an increased release of C and N (Shahzad et al., 2019;Thilakarathna and Hernandez-Ramirez, 2021). The FAPROTAX results also confirmed that TA2 increased the relative abundance of bacterial community related to C-cycle and N-cycle (Fig. 7). ...
Article
Soil oxygen (O2) deficiency induced by organic mulching is easy to overlook. Aeration has been shown to potentially alleviate soil hypoxia stress. However, the responses of soil bacterial communities to such mulching-induced hypoxic conditions and aeration remain elusive. Therefore, a three-year field experiment, consisting of mulching (T1), mulching with aeration (TA1, poor aeration; TA2, strong aeration), and no-mulching (CK) treatments, was conducted in bamboo (Phyllostachys praecox) plantations. According to our results, the strong aeration treatment (TA2) alleviated soil acidification, increased soil nutrient availability, and significantly increased soil O2 content by 18.44% (P < 0.05) when compared with T1. In addition, TA2 significantly increased soil β-glucosidase, invertase, urease, and acid phosphatase activities compared with CK and T1 (P < 0.05). The alpha diversity indices with TA2 treatment were the highest, indicating that aeration increased the species richness and diversity of bacteria. The changes in bacterial community composition associated with TA2 treatment (i.e., an increase in Firmicutes, Verrucomicrobia, and Faecalibacterium abundance and a decrease in Chloroflexi and Bradyrhizobium abundance) were mainly related to nutrient and O2 content. Mantel Test results suggested that soil O2 content and temperature were the key factors shaping bacterial community composition. Structural equation modeling revealed that soil O2 content had a positive and direct influence on bacterial community diversity. Functional annotation of prokaryotic taxa predicted that TA2 significantly increased the relative abundance of bacterial communities associated with nitrification, nitrogen fixation, and ureolysis. Our results demonstrated that optimal soil aeration conditions (17.60% of O2 content) could enhance the diversity and function of soil bacterial communities. Overall, the findings of this study could serve as a benchmark for alleviating soil hypoxia caused by organic mulches, which is important for increasing the functionality of nutrient cycling bacterial communities in the soil.
... Besides, the coverage fraction decreased by 50% (CF 50 ), and the decline rate plateaued; however, the yield (2.37%), NUE (1.44%), and NO 3 -N uptake (1.13%) of CF 10 did not decrease remarkably compared to CF 50 (Fig. 7). The cum.NL increased with an increase in coverage fraction, but a 10% higher coverage fraction did not affect cum.NL, this was because the volatilization of N decreased and NO 3 -N uptake increased to reach a perfect balance (Shahzad et al., 2019;Yin et al., 2019;Xu et al., 2020;Mo et al., 2020). Therefore, the selection of biodegradable films with different degradation rates should consider the local climatic conditions. ...
Article
The residual film and nitrate nitrogen (NO3-N) leaching are the main sources of non-point pollution in arid fields. To solve the above problems, the DNDC model was first calibrated and validated based on data obtained from plastic film mulching (PM), biodegradable film mulching (BM), and no film mulching (NM) studies performed during 2016 and 2017. The NO3-N content in 0–50 cm soil layer, leaching, uptake, balance and use efficiency (NUE) under PM, BM, and NM with topdressing nitrogen (N) amount of 280 kg ha⁻¹ (PM280, BM280, and NM280) were evaluated using observed and simulated data. Additionally, scenario simulation and prediction tests were carried out using the DNDC model to explore the critical topdressing N amount for BM, PM, and NM. These factors were compared for BM with topdressing N amount of 160 kg ha⁻¹ (BM160) and 220 kg ha⁻¹ (BM220). DNDC model showed remarkably high accuracy in simulating the NO3-N content, leaching, uptake, and yield, with R² and NSE (Nash-Sutcliffe efficiency) of 0.88–0.99 and 0.77–0.99, respectively, during validation studies. During the late growth stage, the corn yield, NO3-N uptake, content, cumulative NO3-N leaching (cum.NL), and NUE for BM280 showed an average decrease of 4%, 1.44%, 8.81%, 0.75%, and 2.04% than PM280, respectively. NO3-N content and cum.NL increased markedly with increasing concentration of topdressing N. NO3-N content and cum.NL was increased by 149.03% and 87.33% for BM280 and 46.71% and 40.7% for BM220, respectively, as compared to BM160. The NUE for BM280 decreased by 30.56% and 18.25% compared to BM160 and BM220, respectively. The scenario simulations showed that 200 kg ha⁻¹ is a critical topdressing N application amount for the arid cornfields, with corn yield of 11,132.1 kg ha⁻¹, cum.NL of 121.33 kg ha⁻¹, and NUE of 42.54%, respectively.
... Different T s fluctuations under different mulching treatments occurred mainly in the mulching area. The field with a larger mulching area can effectively decrease the near-ground wind speed, reduce water vapor losses (Shahzad et al., 2019), and regulate T s Hwang et al., 2019). On the other hand, the field with a small mulching area can produce increased soil surface temperature fluctuations due to high radiation reflection and intense near-ground wind speed (Kader et al., 2020). ...
Article
The use of plastic film mulching (PM) has steadily increased in the past few decades due to many advantages compared to no film mulching (NM). However, PM also has many drawbacks, such as producing plastic film residues and causing high temperatures at later crop growth stages. Thus, biodegradable film mulching (BM) has recently been used as an excellent alternative solution. In this study, the effects of three mulching types, including PM, BM, and NM, on soil temperatures (T s) are evaluated using field experiments. Three mulching types with an irrigation depth of 22.5 mm (i.e., PM 22.5 , BM 22.5 , and NM 22.5) and three irrigation depths of 15, 22.5, and 30 mm with BM (i.e., BM 15 , BM 22.5 , and BM 30 , respectively) were compared. Additionally, the T s fluctuations and distributions during different crop growth stages were simulated using HYDRUS (2D/3D). The results showed that HYDRUS (2D/3D) successfully simulated T s with RMSE of 2.11-4.00 • C, EF of 0.63− 0.85, and MRE of 8.1 %-11.6 % during the validation period. There were large differences in T s among PM 22.5 , BM 22.5 , and NM 22.5 in different crop growth stages. In the elongation and tasseling stages, T s under PM 22.5 and BM 22.5 was not significantly different but markedly improved compared with NM 22.5. In the filling and maturation stages, higher variability of T s was observed under BM 22.5 compared with PM 22.5. The standard deviation (SD), the deviation variance (DV), and the kurtosis coefficient (K) under BM 22.5 were by 6.7 %, 32.6 %, and 19.3 % higher than under PM 22.5 , while accumulated soil temperature (AT) and the ratio of effective accumulated soil temperature (AET, ≥10 • C) to AT (R T) decreased by 3.8 % and 4.0 %, respectively. Additionally, apparent differences in T s between BM 22.5 and PM 22.5 appeared mainly in the soil surface layer (0− 10 cm). The area with "optimal T s " (i.e., corn growth is optimal in the T s range of 20− 24 • C) in the 0− 30 cm soil layer increased by 33.5 % under BM 22.5 compared with PM 22.5. Moreover, T s decreased with an increase in the irrigation depth from BM 15 to BM 22.5 , and BM 30 , with the maximum size of the "optimal T s " area under BM 22.5. Generally, BM has more advantages in terms of heat preservation and preventing high temperatures compared with NM and PM, respectively. Therefore, the biodegradable film can be recommended as an alternative material to replace the traditional polyethylene film.
... To the most part studies of soil oxygen have not performed high frequency measurement (see Friedman and Naftaliev, 2012 for example) in part due to the cost of setting permanent measuring devices. The few studies that have employed high frequency measurements of soil oxygen in field conditions, did not relate to the hourly changes in oxygen and how they are affected by edaphic conditions (Kallestad et al., 2008;Liptzin et al., 2011;Owens et al., 2017;Shahzad et al., 2019) . ...
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Alternative water sources for agriculture are in high demand in a world with diminishing fresh water (FW) availability. Treated wastewater (TWW) offers a reliable alternative, but increasing evidence is pointing to damage to TWW irrigated orchards planted in clay soils related to soil hypoxia. The mechanisms responsible for this hypoxia have not been extensively studied to date. The aim of this study was to elucidate meaningful insights into the mechanisms responsible for the hypoxia in TWW irrigated orchards planted in clay soils using a novel approach whereby parameters describing the soil oxygen and water temporal dynamics are analyzed. To that end, soil oxygen and soil water tension (SWT) measurements from a two year field experiment comparing TWW to FW irrigation in an avocado orchard planted in a clay soil (60 % clay) were used. The deterioration in oxygen levels occurred as the irrigation season progressed, and the oxygen availability decreased with depth (10–35 cm depth). During August-September, when the lowest oxygen concentrations were measured, the water content at which oxygen supply matched oxygen consumption at 35-cm depth did not differ between treatments (∼50 mbar), but the TWW irrigated soil experienced ∼47 % more time at wetter conditions. Lower oxygen decline rates were observed in the TWW irrigated plots which countered the previous concept that TWW leads to increased soil oxygen consumption. The findings point towards the rate of soil drying as the prime cause of differences – TWW irrigated plots dried in a rate which is nearly 4-times smaller than that in FW irrigated plots during the dark and light hours, reflecting slower drainage and water uptake respectively. It is suggested that soil hypoxia induced by the low soil drainage in TWW irrigated clay soils impairs tree water uptake, which further hinders the soil oxygen levels. Based on these results management tools are suggested to allow sustainable irrigation with TWW in the future. Furthermore, the work demonstrates how analysis of parameters describing the oxygen hourly changes can be utilized to gain mechanistic insights unto processes affecting the oxygen regime in the soil.
... Plastic mulch significantly increased the relative abundance of Planctomycetes and Latescibacteria, while decreasing the relative abundance of Gemmatimonadetes, Actinobacteria, and Nitrospirae, mainly due to the higher soil moisture and lower oxygen conditions under FM (Shahzad et al., 2019). Members of Planctomycetes were identified as anammox bacteria (Mohamed et al., 2010), and Latescibacteria can survive anoxic conditions (Youssef et al., 2015); changes in the abundance of these two phyla could strongly affect soil N cycling and organic matter (SOM) decomposition. ...
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Floodplain forests belong among the most productive, dynamic and diverse ecosystems on Earth. Only few studies have focused on the carbon dioxide fluxes of these ecosystems. Therefore, this study investigated the spatial heterogeneity in soil CO2 efflux in a floodplain forest located in the southeast of the Czech Republic. The study also examined which environmental parameters influence soil CO2 efflux. Moreover, using these obtained measurements a soil CO2 efflux model was applied. To achieve the aims of this study, soil CO2 efflux on 30 positions in 16 campaigns was measured from May to November during the growing season 2016. The efflux during the experiment period ranged from 1.59 to 8.54 mmolCO2 m �2 s �1. The highest soil CO2 effluxes were observed during the summer period while the lowest values were measured during the autumn. A strong relationship between soil CO2 efflux and soil temperature was found (R2 ¼ 0.79). The estimated mean Q10 for the whole 30 positions was of 2.23. We determined that the spatial heterogeneity of soil CO2 efflux was 20% during our study. The cumulative amount of carbon forest floor released from our experimental forest site calculated from our model was 7.4 (±1.1) tC ha �1 y �1 for 2016. Such data are important for developing our knowledge and understanding about carbon dynamics and to improve carbon models for these ecosystems types.
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Assessment of nitrous oxide (N2O) emission factor (EF) for N2O emission inventory from arable crops fertilized with different nitrogen sources are under increased scrutiny because of discrepancies between the default IPCC EFs and low EFs reported by many researchers. Mixing ratio of leguminous and non-leguminous cover crop residues incorporation and plastic film mulching (PFM) in upland soil has been recommended as a vital agronomic practice to enhance yield and soil quality. However, how these practices together affect N2O emissions, yield-scaled emissions and the EFs remain uncertain. Field experiments spanning two consecutive years were conducted to evaluate the effects of PFM on N2O emissions, yield-scaled emissions and the seasonal EFs in cover crop residues amended soil during maize cultivation. The mixture of barley (Hordeum vulgare) and hairy vetch (Vicia villosa) seeds with 75% recommended dose (RD 140 kg ha⁻¹) and 25% recommended dose (RD 90 kg ha⁻¹), respectively, were broadcasted during the fallow period and 0, 25, 50 and 100% of the total aboveground harvested biomass that correspond to 0, 76, 152 and 304 kg N ha⁻¹ were incorporated before maize transplanting. It was found that the mean seasonal EFs from cover crop residues amended soil under No-mulching (NM) and PFM were 1.13% (ranging from 0.81 to 1.23%) and 1.49% (ranging from 1.02 to 1.63%), respectively, which are comparable to the IPCC (2006) default EF (1%) for emission inventories of N2O from crop residues. The emission fluxes were greatly influenced by NH4⁺N, NO3⁻-N, DOC and DON contents of soil. The cumulative N2O emissions markedly increased with the increase in cover crop residues application rates and it was more prominent under PFM than under NM. However, the yield-scaled emissions markedly decreased under PFM compared to NM due to the improved yield. With relatively low yield-scaled N2O emissions, 25% biomass mixing ratio of barley and hairy vetch (76 kg N ha⁻¹) under PFM could be recommended to enhance yield and to mitigate N2O emissions in an upland maize cropping system.
Article
Ginger (Zingiber officinale Roscoe) is grown in tropical and subtropical regions of the world for its spice and medicinal values. The emergence and early growth of ginger is inherently slow and weed growth can impact on yield. A field experiment comprising different organic mulch viz., paddy straw, coir pith compost, dried coconut leaves, Glycosmis pentaphylla leaves (farmer’s practice), Lantana camara leaves, cowpea plants and plastic mulch black, ash and white colour were compared with non mulched ginger grown under rainfed condition. The experiment was conducted to identify an alternative to suppress weeds, enhance yield and income of small-holder ginger farmer. Maximum height (43.2 cm) and weed control efficiency (72%) was recorded by the treatment application of one season old paddy straw along with green leaf mulch followed by application of Lanthana camara leaves. Application of dried coconut leaves alone at the time of planting recorded maximum benefit cost (B: C) ratio (2.04) followed by the application of one season old paddy straw. White coloured polythene mulch recorded maximum yield (7.52 t ha−1) that was similar with ash coloured polythene mulch and income obtained was less compared to other organic mulches. Application of dried coconut leaves as a mulch for suppressing weeds in ginger is a viable technology which can be practiced in places where coconut is being grown in India. Monocot weeds were less in number and among dicots most predominant weed species were Spermacoce latifolia, Ageratum conyzoides, Oldenlandia auricularia, Cleome rutidosperma and Oxalis corniculata.
Article
Plastic mulching has become a globally applied agricultural practice for its instant economic benefits such as higher yields, earlier harvests, improved fruit quality and increased water-use efficiency. However, knowledge of the sustainability of plastic mulching remains vague in terms of both an environmental and agronomic perspective. This review critically discusses the current understanding of the environmental impact of plastic mulch use by linking knowledge of agricultural benefits and research on the life cycle of plastic mulches with direct and indirect implications for long-term soil quality and ecosystem services. Adverse effects may arise from plastic additives, enhanced pesticide runoff and plastic residues likely to fragment into microplastics but remaining chemically intact and accumulating in soil where they can successively sorb agrochemicals. The quantification of microplastics in soil remains challenging due to the lack of appropriate analytical techniques. The cost and effort of recovering and recycling used mulching films may offset the aforementioned benefits in the long term. However, comparative and long-term agronomic assessments have not yet been conducted. Furthermore, plastic mulches have the potential to alter soil quality by shifting the edaphic biocoenosis (e.g. towards mycotoxigenic fungi), accelerate C/N metabolism eventually depleting soil organic matter stocks, increase soil water repellency and favour the release of greenhouse gases. A substantial process understanding of the interactions between the soil microclimate, water supply and biological activity under plastic mulches is still lacking but required to estimate potential risks for long-term soil quality. Currently, farmers mostly base their decision to apply plastic mulches rather on expected short-term benefits than on the consideration of long-term consequences. Future interdisciplinary research should therefore gain a deeper understanding of the incentives for farmers and public perception from both a psychological and economic perspective in order to develop new support strategies for the transition into a more environment-friendly food production.
Article
Solarization is a method of heating moist soil by covering it with plastic sheets to trap solar radiation. In field experiments in Israel during the summer, maximum soil temperature under plastic cover at the 5-cm depth averaged 46 to 49C. No weeds emerged under the plastic cover during solarization and weed emergence was reduced after its removal. The heating effect from solarization decreased with soil depth. Concentration of O 2 in soil under plastic was similar to that in uncovered controls, but the concentration of CO 2 was markedly higher than in control soil, rising up to 2.4%. Higher temperatures and better residual weed control were produced by transparent than by black plastic, with best results from thin (0.03 mm), transparent polyethylene. Under Israeli summer conditions, 2 to 4 weeks of solarization produced effective control of annual weeds that was still appreciable after 1 yr. Narrow sheets of 20 to 50 cm produced effective weed control in bands. on soil irrigated once before placing the plastic sheets, there was no need to irrigate during solarization. The response of weed species to solarization differed. Many annual weeds, both summer species such as pigweed ( Amaranthus spp.) and common purslane ( Portulaca oleracea L.) and winter species as henbit ( Lamium amplexicaule L.) were well controlled by solarization. Broomrape ( Orobanche crenata Forsk.) was controlled in one experiment. on the other hand, horseweed [ Conyza canadensis (L.) Cronq.] and bull mallow ( Malva niceaensis All.) were relatively resistant, and established perennials escaped the treatment.
Article
Soil respiration is an important component of the net carbon dioxide exchange between agricultural ecosystems and the atmosphere, and reliable estimates of soil respiration are required in carbon balance studies. Most of the field measurements of soil respiration reported in the literature have been made using alkali traps. The use of portable CO 2 analysers in dynamic closed chamber systems is recent. The introduction of this new technique requires its evaluation against existing methods in order to compare new information with older data. Nine intercomparisons between dynamic systems and alkali traps were made. Measurements of F c,s obtained by both chambers showed a good agreement in all but two comparisons in which alkali trap measurements were lower than the dynamic chamber by about 22%. This first report of agreement between both techniques suggests that many measurements made in the past using alkali traps may be comparable to the measurements made more recently using the dynamic chambers. Analysis of the soil temperature and CO 2 concentration inside the alkali traps failed to explain why the alkali traps occasionally underestimated the fluxes. Soil respiration measured with a dynamic closed chamber were also compared to eddy-correlation measurements. The results did not reveal any consistent bias between techniques but the scattering was large. This dispersion is likely the result of the difference between the areas measured by the two techniques. Key words: Carbon dioxide, greenhouse gases, CO 2 flux, soil carbon
Article
The upward flux of carbon dioxide at the soil surface was calculated from the weight increase of soda lime granules exposed inside a glass tank covering 400 cm2 soil. Over bare soil, the flux varied annually with a summer maximum of about 7 g CO2 m-2 day-1, a winter minimum of 1 g m-2 day-1, and a Q10 of 3. The contribution of root respiration, calculated from the difference between the fluxes over fallow and cropped soil, was usually about 1-3 g m-2 day-1. From dry matter determinations, the amount of soil carbon assimilated by crops was about 6% of the net carbon uptake for rapidly growing grass in spring and about 20% for other crops during the summer. The top 46 cm of the soil profile contained 12 kg carbon m-2 and lost 0.4 kg m-2 annually by respiration. The corresponding half-life of soil organic matter is 22 years. The variation of carbon dioxide concentration and rate of photosynthesis with soil flux depends on wind speed and atmospheric stability. In most weather, atmospheric mixing is so vigorous that the concentrations in the canopy and in the free atmosphere are very similar (c. 300 ppm), and photosynthesis is independent of soil flux. In glass-houses, where mixing is less, the concentration may be much less than 300 ppm. In chosen conditions gross photosynthesis increased by 30% when the upward flux of carbon dioxide below the canopy increased by 10 g m-2 day-1.
Article
Understanding plant-soil relationships may help maximize crop productivity while maintaining and improving soil quality. Field experiments were conducted in 2006 and 2007 at the Dryland Agricultural Experimental Station of the Loess Plateau, Lanzhou University, China, to determine the effects of various ridge-furrow and plastic-mulching techniques on the growth and yield of maize (Zea mays L) and soil biochemical properties. Five treatments were designed: (1) flat-plot sowing without ridge-furrow mulching (CK), (2) large (80 cm) and small (40 cm) ridges alternated and fully mulched with plastic (DRM), (3) on-furrow sowing with plastic mulch applied only on the ridge at a row spacing of 60 cm and 40 cm alternatively (RM), (4) flat-plot sowing with plastic mulch at a row spacing of 60 cm and 40 cm alternatively (NM), and (5) flat-plot sowing with plastic mulch at a row spacing of 80 cm and 40 cm alternatively (WM). The results showed that film mulching enhanced soil microbial biomass: where microbial biomass carbon (MBC) in the DRM treatment reached 633 mg kg(-1) at harvest in 2007, three times the MBC of the CK. The MBC:SOC ratios were 8.8%, 7.1%, 5.7% and 5.4% in DRM, RM, NM and WM, respectively. The ridge-furrow with plastic-mulching increased soil light fraction carbon (LFOC) in both years, averaging up to 1.04g kg(-1) at harvest. Underground plant biomass increased substantially in the mulching treatments, especially in DRM. Positive correlations were found between total biomass and LFOC. between MBC and LFOC, and between MBC and available phosphorus (AP), but a negative correlation between SOC and soil mineral nitrogen (MN). The carbon to phosphorus (C/P) ratio was highest in DRM among treatments, but the content of SOC. MN, and C/N ratio in DRM was lowest, suggesting that the DRM treatment strengthened the interactions between maize and soil, and that the increased content of LFOC with time provides a basis for increasing productivity in future years. In conclusion, the ridge-furrow and plastic-mulching technique brought about a challenge in maintaining soil fertility, but this technology provides a potential opportunity of substantially increasing crop yields in semiarid rainfed regions.
Article
The flux of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) from brown lowland soils in a satsuma mandarin (Citrus unshiu Marcow, 'Silverhill', 31 years old) orchard located in Okitsu, central Japan facing the North Pacific Ocean, was measured once a week from March 2001 to February 2002 using the closed chamber method. Two categories of treatment, mulching and non-mulching, were used in the experimental field by covering the soil surface with a moisture-permeable and waterproof sheet in the latter half of fruit growing season from mid-September to mid-December in 2001. The annual N2O emission and the amount of total nitrogen fertilized were 93 mg N/m(2)/year and 27.0 g N/m(2)/year for the non-mulching treatment and 55 mg N/m(2)/year and 18.9 g N/m2/year for the mulching treatment, respectively. No significant difference was found in the N2O emission factor between mulching (0.34%) and non-mulching (0.29%) treatment. These emission factors were much lower than the average value (0.62%) for upland fields in Japan and the IPCC default value of 1.25%. On the other hand, a small amount of atmospheric methane was absorbed into the surface soils throughout the year. The annual uptake of CH4 was 24 and 17 mg CH4/m(2)/year for the non-mulching and mulching treatment, respectively, with no significant difference between the two treatments. Annual CO2 emission with the non-mulching and mulching treatment was 1.45 and 0.89 kg CO2/m(2)/year, respectively. The difference in the amount of each gas emission between the two treatments was discussed with respect to the soil temperature, water-filled pore space (WFPS), the timing and amount of nitrogen fertilized, and the effect of mulching.
Article
A simple method for measuring oxygen level in the root zone of plants growing in non-saturated humidity conditions is presented. The oxygen concentration of soil air under layers of compost mulch was measured using galvanic oxygen sensors mounted in diffusion chambers and the results were compared with infrared gas analyses of soil air samples. Two trials showed that a moderate (5–10 cm) layer of compost mulch has no major effect on the oxygen level in soil under dry conditions, while a 15-cm mulch layer results in an oxygen depletion of short duration. In wet conditions, oxygen depletion under even a 5-cm layer of compost mulch results in a significant lowering of the oxygen level in soil and lasts for days in conditions of much precipitation. Root functions can be negatively affected at <10% oxygen concentration of the soil air. Compost mulch can decrease oxygen concentrations to well below this critical level in wet or poorly drained soils and thereby contribute to the stress load of urban trees. The use of galvanic oxygen sensors proved to be a simple and low-cost method for measuring soil-air oxygen.
Article
The effect of the obstruction of solid on the permeability of porous media is examined. From this it is concluded that, in Penman's equation for diffusion of gases through porous media, the constant 0.66 should be replaced by at where a is the porosity.
Article
In northwestern China, there has been a change from traditional cultivation system (TC) with no mulching and flood irrigation to a more modern cultivation system (MC) using plastic film mulching with drip irrigation. A field study was conducted to compare soil CO2 concentrations and soil surface CO2 fluxes between TC and MC systems during a cotton growing season. CO2 concentrations in the soil profile were higher in the MC system (3107-9212 μL L−1) than in the TC system (1275-8994 μL L−1) but the rate of CO2 flux was lower in the MC system. Possible reasons for this included decreased gas diffusion and higher soil moisture due to the mulching cover in the MC system, and the consumption of soil CO2 by weathering reactions. Over the whole cotton growing season, accumulated rates of CO2 flux were 300 and 394 g C m−2 for the MC and TC systems, respectively. When agricultural practices were converted from traditional cultivation to a plastic film mulching system, soil CO2 emissions could be reduced by approximately 100 g C m−2 year−1 in agricultural lands in arid and/or semi-arid areas of northern and northwestern China.
Article
Microbial biomass C (MBC) is one of the soil properties used as an indicator for the fertility status of a soil. A study was conducted on a semi-arid Loess Plateau in China. The field was planted with spring wheat and mulched with plastic film for various lengths of time. Our primary objectives were to (i) explore the influence of film mulching on soil MBC and soil fertility, and (ii) seek an effective approach of maintaining and improving sustainability of cropland mulched with plastic film in two growing seasons. Four treatments were tested, non-mulching (M0), mulching for 30 days after sowing (M30), mulching for 60 DAS (M60) and mulching for the whole growing period (Mw). An increasing air temperature with time within the growing season promoted soil MBC in the two growing seasons, but a severe drought led to a lower MBC in 2000 compared with the wet year of 1999. Film mulching promoted MBC significantly in the 2 years, but decreased soil organic carbon (SOC). SOC is very low in the experimental soil, accounting for the higher MBC/SOC ratio compared with ratios reported by others. The SOC is greatly reduced in the non-mulched and the Mw treatments compared to the M30 and M60 treatments. In conclusion, the benefits of film mulching in semi-arid agricultural systems are enormous but realizing their full potential depends on how long the mulching material is maintained during the growing season. In the system tested, it is desirable to mulch the plots for 30–60 DAS in order to enhance microbial biomass and cycling of nutrients and also to provide a more stable soil micro-environment that generates more residues in the rhizosphere.
Article
The impact of tillage systems on soil CO2 emission is a complex issue as different soil types are managed in various ways, from no-till to intensive land preparation. In southern Brazil, the adoption of a new management option has arisen most recently, with no-tillage as well as no burning of crops residues left on soil surface after harvesting, especially in sugar cane areas. Although such practice has helped to restore soil carbon, the tillage impact on soil carbon loss in such areas has not been widely investigated. This study evaluated the effect of moldboard plowing followed by offset disk harrow and chisel plowing on clay oxisol CO2 emission in a sugar cane field treated with no-tillage and high crop residues input in the last 6 years. Emissions after tillage were compared to undisturbed soil CO2 emissions during a 4-week period by using an LI-6400 system coupled to a portable soil chamber. Conventional tillage caused the highest emission during almost the whole period studied, except for the efflux immediately following tillage, when the reduced plot produced the highest peak. The lowest emissions were recorded 7 days after tillage, at the end of a dry period, when soil moisture reached its lowest rate. A linear regression between soil CO2 effluxes and soil moisture in the no-till and conventional plots corroborate the fact that moisture, and not soil temperature, was a controlling factor. Total soil CO2 loss was huge and indicates that the adoption of reduced tillage would considerably decrease soil carbon dioxide emission in our region, particularly during the summer season and when growers leave large amounts of crop residues on the soil surface. Although it is known that crop residues are important for restoring soil carbon, our result indicates that an amount equivalent to approximately 30% of annual crop carbon residues could be transferred to the atmosphere, in a period of 4 weeks only, when conventional tillage is applied on no-tilled soils.
Soil air regime and soil structure of the fields under plastic mulching
  • Y Chen
  • L Xiaoyi
  • L Mingguo
Chen, Y., Xiaoyi, L., Mingguo, L., 1995. Soil air regime and soil structure of the fields under plastic mulching. J. Shengyang Agric. Univ. 261, 146-151.
Measuring Small Volumes of CO 2 with the Li-7000. Application Note IRG4-107
  • Li-Cor
LI-COR, 2007. Measuring Small Volumes of CO 2 with the Li-7000. Application Note IRG4-107. Li-COR Biosciences, Lincoln, NE.
Soil air regime and soil structure of the fields under plastic mulching
  • Chen