Decomposition Of Crop Residues Research Articles

Evaluating the Impact of Integrated Nutrient Management Practices on Land Productivity, Crop Residue Decomposition and Abundance of Soil Organisms in a Banana Plantation in Sri Lanka

The fertilization practices heavily influence the decomposition rate of organic materials added to soil. Hence, the nutrient management strategies that aim to improve crop yields may not necessarily support organic carbon accumulation in soil and overall soil fertility. This study investigated how land productivity, crop residue decomposition and diversity of soil organisms were affected by the combined use of chemical fertilizers (CF) and poultry manure (PM) in a banana plantation in Buttala, Sri Lanka. Banana yield, soil properties and decomposition of crop residues were studied in six treatments as, CF1+PM1, CF1+PM2, CF1+PM3, CF2 +PM1, CF2+PM2, and CF2+PM3. CF1 and CF2 correspond with 75% and 100% of recommended CF application rate. PM1, PM2 and PM3 correspond with PM application rates of 0, 2.5 and 5 kg/plant. Crop residue decomposition was assessed using litter bags containing two litter materials as banana pseudo-stem pieces and banana leaves and placed at two depths (surface and at 7.5 cm depth). Litter bags were recovered at 17, 31 and 45 days after placement (DAP) and weight loss of crop residues was determined. The application of poultry manure significantly increased (P<0.01) banana yield at first harvest and decreased (P<0.1) bulk density. Type of material and time of exposure to decomposition had significant effects (P<0.05) on litter decomposition but depth of placement and nutrient management strategy had no significant effect (P>0.05) on decomposition. By 45 DAP pseudo-stems were degraded more than leaves (67.47±13.99 % and 46.90±5.76 %, respectively). The abundance of culturable bacteria and cellulose decomposers in soil and the abundance of soil fauna in decomposing litter were significantly (P<0.1) increased with the PM application to soil. In conclusion, in the studied banana plantation, incorporation of PM in nutrient management increased land productivity and had positive impact on some soil properties, which are important determinants of soil fertility but did not register any effects on crop residue decomposition during the study period.

Improvement of Saline–Alkali Soil and Straw Degradation Efficiency in Cold and Arid Areas Using Klebsiella sp. and Pseudomonas sp.

Corn straw is an important renewable resource, which could improve the quality of saline–alkali cultivated land. However, the slow decomposition of crop residues in cold, arid, and saline–alkali soils can lead to serious resource waste and ecological crises. The use of beneficial microorganisms with degradation functions could solve these problems. In this study, three types of saline–alkali soil with low, medium, and high salinity levels were used in the straw-returning experiment. The experiment was conducted with four treatments: GF2 (Klebsiella sp.), GF7 (Pseudomonas sp.), GF2+GF7, and CK (control without bacteria). Microbial characteristics, straw degradation efficiency, element release rate, and soil factors were compared, and random forest linear regression and partial least squares path modeling analysis methods were utilized. The results indicated that the degradation of bacterial metabolites, the efficiency of corn stover degradation, the efficiency of component degradation, and the release rates of elements (C, N, P, and K) initially increased and then decreased with the increase in salinity. At the maximum value of moderately saline–alkali soil, the effect of GF2+GF7 treatment was significantly better than that of other treatments (p < 0.05). Given the interactive effects of saline–alkali soil and microbial factors, the application of exogenous degrading bacteria could significantly increase soil enzyme activity and soil available nutrients, as well as regulate the salt–alkali ion balance in soil. The cation exchange capacity (9.13%, p < 0.01) was the primary driving force for the degradation rate of straw in saline–alkali soil with different degrees of salinization under the influence of exogenous degrading bacteria. Straw decomposition directly affected the soil chemical properties and indirectly affected soil enzyme activity. The results of this study would provide new strategies and insights into the utilization of microbial resources to promote straw degradation.

Soil organic carbon pools as influenced by 21 years of conservation agriculture management practices in Saskatchewan

Soil organic carbon (SOC) content is a key metric of soil quality and limited work has been done to examine the effect of long-term conservation agriculture management practices (CAMP) on SOC pools within western Canadian soils. We assessed the nature and permanence of sequestered SOC within 90 diverse Saskatchewan surface (0–10 cm) agricultural soils before and after 21 years of CAMP. Comparisons were made of total SOC, labile and dynamic SOC fractions (light fraction, water-extractable, and microbial biomass), respirable CO2–C during a 6-week incubation, along with spectroscopic characterization using 13C/12C stable isotope ratio and ATR-FTIR. Among soil climatic zones, the SOC content increased in the semi-arid Brown and Dark Brown soils, ranging from 2.4 to 3.7 Mg C ha−1 (111.4–187.7 kg C ha−1 year−1), but did not change in the subhumid Black, Dark Gray, and Gray soils. Overall, soils having the smallest initial SOC level were most responsive to CAMP and accumulated more SOC. According to the δ13C data, CAMP appeared to reduce annual crop moisture stress, especially within the Brown soil zone. Decreased light fraction and water-extractable SOC contents in Black, Dark Gray, and Gray soils could reflect more intense decomposition and greater surface stratification of crop residues. Brown soils experienced the largest increase in microbial biomass-C content. The CO2–C emissions from the Brown, Dark Brown, and Gray soils under CAMP suggest greater SOC stability in 2018 compared with 1996. The ATR-FTIR data pointed to enhanced SOC persistence, via more stabilized SOC forms and mineral-associated organic C fractions.

Biopreparations for the decomposition of crop residues.

Recently, there has been growing interest in biopreparations that intensify the decomposition of crop residues. These preparations can promote nutrient cycling and soil fertility, ultimately supporting healthy plant growth and increasing agricultural productivity. However, the development and commercialization of biopreparations poses unique challenges. Producers of biopreparations struggle to develop highly effective preparations, which then face regulatory hurdles and must win market acceptance. This literature review provides up-to-date data on microbial preparations available commercially on the European market, along with information on current relevant regulations. Challenges for the development and commercialization of new biopreparations are also discussed. The development and commercialization of biopreparations require a comprehensive approach that addresses the complex interplay of microbial and environmental factors. The need for more specific regulations on biopreparations for decomposing crop residues, clearer instructions on their use, and further research on the overall impact of biopreparations on the soil metabolome and optimal conditions for their application were indicated. Moreover, manufacturers should prioritize the development of high-quality products that meet the needs of farmers and address concerns about environmental impact and public acceptance.

Greenhouse gas emissions during decomposition of cover crops and poultry litter with simulated tillage in 90‐day soil incubations

AbstractInvestigating the impact of cover crops and manure on soil greenhouse gas (GHG) emissions is crucial for advancing our understanding of the climate‐smart potential of organic management practices. This soil incubation experiment was conducted to investigate the combined effects of manure and cover crop residue decomposition on soil carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions under simulated tillage conditions. Undisturbed soil cores, collected from an organic cotton (Gossypium hirsutum L.) field experiment, were incubated for 90 days in a 2 × 4 factorial design for 2 consecutive years. Four combinations of cover crop and poultry litter (PL) residues were the primary treatment factor. The amount of residues added in the incubation study reflected the cover crop biomass produced under field conditions and the amount of PL applied in the field. Residue treatments included PL only at the full application rate (250 kg ha−1), PL with oat (Avena sativa L.), PL with turnip (Brassica rapa subsp. rapa), and half the rate of PL with Austrian winter pea (Pisum sativum) (AWP). The residues were either soil incorporated or surface applied to simulate disking and no‐till field conditions. On average, 3.5% of applied carbon escaped as CO2 during the 90‐day incubation period across treatments. Similarly, on average, 0.75% of applied nitrogen escaped as N2O. The proportion of nitrogen emitted as N2O under simulated no‐till was 81.2% higher in 2020 (P < 0.05) compared to conventional tillage. In 2021, N2O emission was 35.8% higher (P < 0.1). When normalized over the amount of carbon added, total CO2 equivalent GHG emissions were the highest in the legume AWP treatment for both years. However, neither residue types nor simulated tillage affected net soil CH4 uptake (P > 0.1). While no‐till practices may increase soil total carbon and nitrogen stocks during the cover crops and manure decomposition, the impact on GHG emissions depends on residue type and should be considered in estimating the climate‐smart potential of organic management practices.

Nitrous oxide emissions from soybean in response to drained and undrained soils and previous corn nitrogen management.

While corn (Zea mays L.)-soybean (Glycine max. Merr. L) is a predominant rotation system in the US Midwest the residual effect of nitrogen (N) fertilization to corn on the following year's soybean and N2O emissions under different soil drainage conditions has not been studied. Our objective was to quantify agronomic parameters and season-long N2O emissions from soybean as affected by N management (0-N and optimum N rate of 135kg N ha-1 as single or split application) during the previous corn crop under drained and undrained systems. Urea was applied to corn, and residual N effects were measured on soybean the following year in a poorly drained soil with and without subsurface tile drainage. Drainage reduced N2O emissions in one of three growing seasons but had no effect on soybean yield or N removal in grain. Nitrogen management in the previous corn crop had no effect on soybean grain yield, N removal, or N2O emissions during the soybean phase. Even though soybean symbiotically fixes N and removes more N in grain than corn, N2O emissions were more than two times greater during the corn phase (mean=1.83kg N ha-1) due to N fertilization than during the soybean phase (mean=0.80kg N ha-1). Also, N2O emissions in the corn years were increased possibly due to decomposition of the previous year's soybean crop residue compared to corn residue decomposition in the soybean years. Tile drainage, especially where wet soil conditions are prevalent, is a viable option to mitigate agricultural N2O emissions.

Cover crop residue decomposition triggered soil oxygen depletion and promoted nitrous oxide emissions

Cover cropping is a promising strategy to improve soil health, but it may also trigger greenhouse gas emissions, especially nitrous oxide (N2O). Beyond nitrogen (N) availability, cover crop residue decomposition may accelerate heterotrophic respiration to limit soil O2 availability, hence promote N2O emissions from denitrification under sub-optimal water-filled pore space (WFPS) conditions that are typically not conducive to large N2O production. We conducted a 21-day incubation experiment to examine the effects of contrasting cover crop residue (grass vs legume) decomposition on soil O2 and biogeochemical changes to influence N2O and CO2 emissions from 15N labeled fertilized soils under 50% and 80% WFPS levels. Irrespective of cover crop type, mixing cover crop residue with N fertilizer resulted in high cumulative N2O emissions under both WFPS conditions. In the absence of cover crop residues, the N fertilizer effect of N2O was only realized under 80% WFPS, whereas it was comparable to the control under 50% WFPS. The N2O peaks under 50% WFPS coincided with soil O2 depletion and concomitant high CO2 emissions when cover crop residues were mixed with N fertilizer. While N fertilizer largely contributed to the total N2O emissions from the cover crop treatments, soil organic matter and/or cover crop residue derived N2O had a greater contribution under 50% than 80% WFPS. Our results underscore the importance of N2O emissions from cover crop-based fertilized systems under relatively lower WFPS via a mechanism of respiration-induced anoxia and highlight potential risks of underestimating N2O emissions under sole reliance on WFPS.

Taxon-specific ability of saprophagous soil macrofauna to reintegrate carbon from agricultural waste into soil

Saprophagous soil macroinvertebrates may potentially degrade agricultural wastes. However, it is not known, to what extent and representatives of which taxa may help reintegrating carbon from crop residues back into soil without triggering massive carbon release into the atmosphere. To tackle this problem, we conducted a three-month-long microcosm experiment with 21 different species of macrofauna (each treatment replicated four times) belonging to 13 families to test their ability to degrade wheat straw. Simultaneously CO2 release from the microcosms was measured. Five species did not survive under experimental conditions. Among the remaining 16 species, three significantly increased wheat straw decomposition with Oryctes nasicornis larvae having inflicted the highest straw mass loss (64%) in comparison with the control, where no animals were added (29%). None of the tested species increased cumulative CO2 evolution from the microcosms, while two species significantly reduced it. The reduction of carbon loss with aerobic respiration was recorded for Cetonia aurata larvae and the earthworm Dendrobaena veneta (respectively 2.5 and 2-fold in relation to the control – 53.8±4.6 mg CO2-C g−1 soil dry weight during the entire experiment). The original integrative Carbon Sequestration Index by Macrofauna (CSIM) calculated for both of the measured parameters suggests that the woodlouse Armadillidium vulgare and to a smaller extent the earthworm D. veneta appear to be the most promising organisms for industrial climate-friendly organic waste recycling in terms of survival, straw processing and simultaneous reduction of CO2 emissions from soil. Our results proved that the engagement of saprophagous macrofauna in crop residue decomposition is a viable technique of carbon reincorporation into the soil. It is accompanied with CO2 release mitigation into the atmosphere.

Residual Effects of Microbial Treated Paddy Residues Applied to Zero Till Maize on Growth and Yield of Summer Greengram

Background: Farmers’ conventional tillage and residue removal practices in rice-maize-greengram systems in India are input-intensive, costly and soil degradative. A number of soil quality issues have emerged due to continuous cropping and burning of residues threatening the sustainability of rice based cropping systems for the last more than four decades. Nevertheless, the in-situ or in-field decomposition of crop residue using microbial inoculum is rarely studied. This necessitated the use of microbial consortia developed by a combination of potent strains of fungi which can perform harmoniously for rapid decomposition of crop residues. Methods: A field experiment was conducted during 2020-21 and 2021-22 with eight residue-management treatments and three fertility levels to zero till maize at college farm, Rajendranagar, PJTSAU using strip plot design and the residual effect on the succeeding greengram was studied. Result: Greengram growth and yield were significantly higher under residual effect of incorporation of residues treated with microbial consortia consisting of Trichoderma viridae, Aspergillus awamori and Phanerocheate spp. along with 300:100:100 kg ha-1 of N, P2O5 and K2O (125% RDF) and P supplied in the form of single super phosphate (SSP) under zero tillage during summer, 2021 and 2022. Growth parameters like plant height, leaf area index, dry matter production and yield attributes like number of pods plant-1, pod length and number of seeds pod-1 in greengram were higher under residue incorporated plots compared to residue burning, removal and retention plots with 125% RDF.

Nitrogen Application and Rhizosphere Effect Exert Opposite Effects on Key Straw-Decomposing Microorganisms in Straw-Amended Soil.

Crop residue decomposition is an important part of the carbon cycle in agricultural ecosystems, and microorganisms are widely recognized as key drivers during this process. However, we still know little about how nitrogen (N) input and rhizosphere effects from the next planting season impact key straw-decomposing microbial communities. Here, we combined amplicon sequencing and DNA-Stable Isotope Probing (DNA-SIP) to explore these effects through a time-series wheat pot experiment with four treatments: 13C-labeled maize straw addition with or without N application (S1N1 and S1N0), and no straw addition with or without N application (S0N1 and S0N0). The results showed that straw addition significantly reduced soil microbial alpha diversity in the early stages. Straw addition changed microbial beta diversity and increased absolute abundance in all stages. Growing plants in straw-amended soil further reduced bacterial alpha diversity, weakened straw-induced changes in beta diversity, and reduced bacterial and fungal absolute abundance in later stages. In contrast, N application could only increase the absolute abundance of soil bacteria and fungi while having little effect on alpha and beta diversity. The SIP-based taxonomic analysis of key straw-decomposing bacteria further indicated that the dominant phyla were Actinobacteria and Proteobacteria, with overrepresented genera belonging to Vicinamibacteraceae and Streptomyces. Key straw-decomposing fungi were dominated by Ascomycota, with overrepresented genera belonging to Penicillium and Aspergillus. N application significantly increased the absolute abundance of key straw-decomposing microorganisms; however, this increase was reduced by the rhizosphere effect. Overall, our study identified key straw-decomposing microorganisms in straw-amended soil and demonstrated that they exhibited opposite responses to N application and the rhizosphere effect.

Spring applied phosphorus loss with cover crops in no-till terraced field

Cover crops (CC) can improve phosphorus (P) cycling by reducing water related P losses and contributing to P nutrition of a rotational crop. This is particularly important in claypan soils with freeze-thaw cycles in early spring in the Midwest U.S. This 4-year study (2019–2022) examined the impact of CC monoculture and mix of CC species on P losses from a fertilizer application, and determined the P balance in soil compared to no cover crop (noCC). The CC mix consisted of wheat (Triticum aestivum L.), radish (Raphanus raphanistrum subsp. Sativus), and turnip (Brassica rapa subsp. Rapa) (3xCCmix) in 2019 and 2021 before corn, and cereal rye (Secale cereale L.) was planted as monoculture before soybean in 2020 and 2022. The 3xCCmix had no effect on total phosphorus (TP) and dissolved reactive phosphorus (PO4–P) concentration or load in 2019 and 2021. Cereal rye reduced TP and PO4–P load 70% and 73%, respectively, compared to noCC. The variation in soil moisture, temperature, and net precipitation from fertilizer application until CC termination affected available soil P pools due to variability in CC species P uptake, residue decomposition, and P loss in surface water runoff. Overall, the P budget calculations showed cereal rye had 2.4 kg ha−1 greater P uptake compared to the 3xCCmix species which also reduced P loss in water and had greater differences in soil P status compared to noCC. This study highlights the benefit of CCs in reducing P loss in surface runoff and immobilizing P through plant uptake. However, these effects were minimal with 3xCCmix species and variability in crop residue decomposition from different CC species could affect overall P-soil balance.

Unveiling the driving role of pH on community stability and function during lignocellulose degradation in paddy soil.

Crop straw, a major by-product of agricultural production, is pivotal in maintaining soil health and preserving the ecological environment. While straw incorporation is widely recognized as a sustainable practice, the incomplete decomposition of crop residues poses challenges to plant growth, increasing the risk of pests and diseases. This necessitates a comprehensive investigation. The current study employs a 28-day pot experiment to simulate the degradation of rice straw in paddy soils. The impacts of bioaugmentation and biostimulation on lignocellulose degradation are systematically evaluated. Results indicate a high lignocellulose degradation ability in paddy soil, with over 80% straw weight loss within 28 days. Bioaugmentation with a lignocellulolytic microbial consortium enhances straw degradation during the initial stage (0-14 days). In contrast, biostimulation with readily available nutrients leads to soil acidification, hindering straw degradation and reducing microbial diversity. Furthermore, pH emerges as a critical factor influencing microbial community stability and function during lignocellulose degradation. Microbial co-occurrence network analysis reveals that microorganisms occupy ecological niches associated with different cellulose components. Notably, Module M2, comprising Proteobacteria, Firmicutes, Gemmatimonadota, Actinobacteriota, Bacteroidota, Myxococcota, Halobacterota, and Acidobacteriota, positively correlates with pH and weight loss. This study significantly advances our understanding of microbial mechanisms in soil decomposition, emphasizing the pivotal role of pH in community stability and function in paddy soil. These findings can inform future strategies for managing rice straw while safeguarding soil ecosystem health.

Exploring the Impact of Tillage Methods on Crop Residue Decomposition and Nutrient Release: A Litter Bag Study

Background: Recycling of crop residues has gained attention over the past few decades due to its influence in sustaining the soil fertility and crop production. In this context, it is of crucial to study the effect of crop residue type, placement and tillage on decomposition and nutrient release in tropical agriculture. Methods: We conducted a litter bag decomposition experiment to evaluate the rate of mass loss, carbon (C), nitrogen (N) and phosphorus (P) mineralization from crops residues. We used residues of cotton, maize and cowpea. Result: Result indicated that cowpea and cotton residues decomposed more rapidly than maize residues, with mass loss of 50-65% occurring within 40 days of placement. Plough depth placement resulted in faster decomposition than deep placement, with 78% of initial mass and nutrient contents lost at the end of 120 days. Over 50% of nutrient mineralization occurred in the first 30 days of decomposition from cowpea residues. At the end of the 120th day, 0.28%, 0.19% and 0.30% of total nitrogen content remained out of 2.15%, 0.86% and 1.22% of the initial total nitrogen in cowpea, maize and cotton residues, respectively. More than 48% of residue breakdown and nutrient mineralization occurred in the first 40 days of decomposition, suggesting that farmers can boost crop growth by choosing crop residues with a low and medium C:N ratio and placing residues at a plough depth (0-15 cm) using reduced tillage practices.

Effects of coffee pericarp and litter mulsching on soil microbiomes diversity and functions in a tropical coffee plantation, South China.

In recent decades, ecological cyclic cultivation models have attracted increasing attention, primarily because the decomposition of crop residues and litter enhances soil organic matter content, thereby altering the soil microenvironment and regulating the diversity and functions of soil microbial communities. However, the effects of different coffee waste mulching on the diversity of soil microbial communities and their functions are still unclear. Therefore, this study set up four kinds of covering treatments: uncovered coffee waste (C), covered coffee litter (L), covered coffee pericarp (P), and both covered coffee litter and pericarp (PL). The results showed that compared to the control, coffee pericarp mulching significantly increased the soil available potassium (SAK) content by 18.45% and alkali hydrolyzed N (SAN) content by 17.29%. Furthermore, coffee pericarp mulching significantly increased bacterial richness and diversity by 7.75 and 2.79%, respectively, while litter mulching had little effect on bacterial abundance and diversity was smaller. The pericarp mulching significantly increased the abundance of Proteus by 22.35% and the abundance of Chlamydomonas by 80.04%, but significantly decreased the abundance of Cyanobacteria by 68.38%, while the coffee litter mulching significantly increased the abundance of Chlamydomonas by 48.28%, but significantly decreased the abundance of Cyanobacteria by 73.98%. The increase in soil SAK promoted bacterial Anoxygenic_photoautotrophy, Nitrogen_respiration, Nitrate_respiration, Nitrite_respiration, and Denitrification functions. The above results indicate that the increase in available soil potassium and alkali hydrolyzed N content under coffee pericarp cover is the main reason for promoting the diversity and richness of bacterial community and promoting the changes in bacterial community structure and function. The use of coffee pericarps in coffee plantations for ecological recycling helps to improve the diversity of the soil microbial community and maintain the relative stability of the microbial community structure and function, promoting soil health conservation and the sustainable development of related industries.

Regenerative agriculture through indigenous practice of using remains of livestock feed residues as a manure to boost groundnut productivity

Cow represents Mother Earth, as it is a source of goodness, its milk nourishes all creatures and dung is store house of millions of microorganisms’ acts as source of organic manure and her urine aids in decomposition of crop residues. It’s in practice for millennium but recently due to introduction of chemical fertilizer found to be disappearing in the farming community coupled with reduction in the livestock population. Application of manure prepared from livestock feed for four years resulted in mean groundnut pod yield of 1665 kg/ha as against application of FYM i.e., 1108 and control 818 kg/ha.

Soil carbon mineralization, enzyme activities, and crop residue decomposition under varying soil moisture regimes

AbstractIn the Lower Mississippi River Basin, farmlands are flooded in late fall and winter by impeding drainage to provide a habitat for migratory birds stopover. A laboratory incubation study was conducted to study the influence of temporary wetting of these soils on carbon (C) and nitrogen (N) mineralization from residue decomposition. Surface soils (0–15 cm) were collected from fields with clay and silty clay loam soils. Both soils were incubated with five crop residues—corn (Zea mays), soybean (Glycine max), cotton (Gossypium hirsutum), sorghum (Sorghum bicolor), and sweet potato (Ipomea batatus)—at 50% and 100% water holding capacity (WHC). Soil carbon dioxide (CO2) efflux was measured during 74 days of incubation. Soil moisture had the largest effect on soil CO2 efflux and most of the enzyme activities followed by residue and soil type. Cumulative soil CO2 efflux was reduced by 46% at 100% WHC compared to 50% WHC. Clay soil had higher cumulative CO2 efflux, aryl sulfatase, aryl phosphatase, and β‐N‐acetyl glucose aminidase activities than silty clay loam soil. Residue type had the largest effect on post‐incubation soil inorganic‐N, remaining biomass, and residue C and residue N. Sweet potato residue had the lowest remaining biomass, significantly lower than cotton, corn, and sorghum, but statistically similar to soybean. After incubation, residue N concentration had a positive association with cumulative CO2 efflux and a negative association with remaining residue biomass percentage. Winter flooding might limit the loss of soil C as CO2 depending on the crops grown and soil type.

Responses of carbon and microbial community structure to soil nitrogen status vary between maize and potato residue decomposition

Plant residue decomposition is a core process in the soil carbon (C) cycle. Soil nitrogen (N) status regulates organic C chemical structure during crop residue decomposition and subsequent C sequestration significantly. Therefore, understanding how soil N status influences changes in organic C chemical structure during residue decomposition is crucial for effective C management in croplands. In this study, maize (M) and potato-monoculture (P) soils with two N statuses (N0, unfertilized; and N2, 250 and 125 kg N ha−1 for M and P, respectively) were used as decomposition environments to conduct 6-month decomposition of maize and potato residue. According to the results, soil N status had no significant effect on mass loss but changed the organic C chemical structure for both residues. Alkyl C and aliphaticity increased in maize residue but decreased in potato residue under N2 relative to under N0. High N availability increased bacterial-fungi interactions, abundance of cellulose and chitin degradation genes (exoglucanase and chitinase), and enzyme activity (chitinase and sucrase) in maize residue. However, the response of potato residue to N status was opposite to that of maize residue. The structural equation model indicated that the increase in soil NO3−-N reduced residue C/N, changed microbial community structure and keystone species in residues, and increased enzyme activities, in turn altering recalcitrant C contents in the decomposed residues. Our results highlight the differential impact of soil N status on organic C chemical structure in different residues, and the coupling relationship between microbial communities and organic C structure during residue decomposition in farmland soil.

Cover crop residue quality regulates litter decomposition dynamics and soil carbon mineralization kinetics in semi-arid cropping systems

Cover crop residue addition provides several soil health benefits and serves as a precursor for storing soil organic carbon (SOC). However, information on residue decomposition dynamics and its contribution to soil carbon (C) and nitrogen (N) cycling in arid and semi-arid environments is limited. This study evaluated cover crop residue decomposition in field conditions and C mineralization kinetics in laboratory conditions. For the field experiment, approximately 20 g of Austrian winter pea (Pisum sativum subsp. arvense L.), turnip (Brassica rapa subsp. rapa L.), and triticale (×Triticosecale Wittmack) cover crop residues were kept in litter bags and placed on the soil surface before subsequent forage sorghum (Sorghum bicolor L. Moench) planting in ongoing cover crops study plots. Litter bags were collected every other week (12 destructive samplings) to evaluate the remaining dry matter and C and N contents. The decomposition data were plotted with first order kinetics and exponential models to describe the model fit. To study C mineralization kinetics, a 10-week incubation was set up in a laboratory with Austrian winter pea, turnip, and triticale cover crops and native grass, wheat, and sorghum residues. Carbon mineralization rates were evaluated with three statistical models (first order kinetics and single and double exponential). The exponential model best described the cover crop residue decomposition kinetics in the field. After 98 days, the residue decomposition was higher with Austrian winter pea (47 %), followed by turnip and triticale with ∼40 % biomass decomposition. Residue types and quality both affected the decomposition rates. The C mineralization rate correlated with initial N content (r = 0.87, P < 0.05), C: N ratio (r = −0.88, P < 0.05), and lignin: N (r = −0.87, P < 0.05). While the single exponential model explained field decomposition dynamics, the double exponential decay model best fitted the observed C mineralization trend among the three models. The decay models from our study can be applied to estimate the decomposition dynamics of other winter cover crop residues in similar agroecosystems. This study demonstrated that selecting suitable cover crops and mixtures is critical for maximizing soil C sequestration and N availability in subsequent crops in cover crop-integrated semi-arid cropping systems.

Isotopic evidence for the effects of earthworm and straw amendment on root carbon uptake of upland rice and maize

The role of earthworms in the direct transfer of dissolved soil organic carbon to plants is poorly understood. We quantified this effect by examining the root uptake of carbon from 13C-labeled rice straw in a greenhouse experiment with three non-flooded Philippine soils that greatly differed in texture (from light sandy to loam). Measurements of carbon stable isotope signatures of aerobic rice and maize over a two-month period revealed that earthworms positively affected 13C transfer from rice straw to rice plants but not to maize plants. However, this effect was significant only in loamy and not in sandy soils. Although the direct uptake of dissolved carbon from soil had no impact on rice production, it indicated a widely ignored option to mitigate carbon loss from crop residue decomposition and associated climate risks. Its enhancement by earthworms confirms the important role of this taxon as soil engineers.

Integrated systems improve the sustainability of soybean cultivation in the tropical region

Inter-cropping between annual crops with tropical forages through integration crop-livestock systems (ICL) is considered a sustainable option to increase crop diversity and soybean productivity. In this study, we evaluated (1) the biomass production, desiccation efficiency, nutrient accumulation, and biomass decomposition of soil crop residues produced by Panicum maximum plants intercropped with maize in two different sowing methods during the second harvest and (2) investigated how soil crop residues impact the productivity of soybean. The experiment was conducted in a complete block design with three replicates. We compared conventional soybean cultivation with soybean cultivated over soil crop residues produced by a previous integration between maize and two Panicum maximum cultivars: Tamani and Zuri guinea grass, within and between rows of maize plants. Our results showed that Tamani guinea grass showed the highest desiccation efficiency. Zuri and Tamani guinea grass cultivated within and between maize plants resulted in higher biomass production and nutrient cycling potential, resulting in an increase of 28.4% in soybean productivity, compared to soybean grown without soil crop residues. We concluded that ICL system is an efficient method to increase the sustainability of soybean cultivation.