Residue Retention Research Articles

Germination ecology of Chenopodium album L. and implications for weed management.

Chenopodium album L. is a troublesome annual species in various cropping systems, and a sound knowledge of the ecological response of C. album germination to environmental factors would suggest suitable management strategies for inhibiting its spread. Preliminary laboratory-based research was conducted to investigate germination and emergence requirements of C. album under various environmental conditions (e.g., photoperiods, constant temperature, salinity, moisture, soil pH, burial depth, and oat crop residue). Results showed C. album seeds were found to be photoblastic, with only 13% germination in darkness. The maximum germination (94%) of C. album occurred at an optimal temperature of 25°C, and the depressive effect of other temperatures on germination was more severe at lower rather than higher temperatures. Seed germination was suitably tolerant of salinity and osmotic potential, with germination observed at 200 mM NaCl (37.0%) and -0.8 MPa (20%), respectively. Germination was relatively uniform (88–92%) at pH levels ranging from 4 to 10. The maximum germination of C. album was observed on the soil surface, with no or rare emergence of seeds at a burial depth of 2 cm or under 7000 kg ha-1 oat straw cover, respectively. Information provided by this study will help to develop more sustainable and effective integrated weed management strategies for the control of C. album, including (i) a shallow-tillage procedures to bury weed seeds in conventional-tillage systems and (ii) oat residue retention or coverage on the soil surface in no-tillage systems.

Identifying effective agricultural management practices for climate change adaptation and mitigation: A win-win strategy in South-Eastern Australia

CONTEXTFarming systems face dual pressures of reducing greenhouse gas (GHG) emissions to mitigate climate change and safeguarding food security to adapt to climate change. Building soil organic carbon (SOC) is proposed as a key strategy for climate change mitigation and adaptation. However, practices that increase SOC may also increase nitrous oxide (N2O) emissions, and impact crop yields and on-farm income. A comprehensive assessment of the effects of different management practices on trade-offs between GHG emissions and agricultural systems profitability under climate change is needed. OBJECTIVEWe aimed to: (1) analyze the long-term trends of SOC and N2O emissions, and ascertain whether the croplands of the study region are net GHG sources or sinks under climate change; (2) quantify the GHG abatement on a gross margin basis; (3) identify effective management practices that could achieve a win-win strategy; and (4) investigate sources of uncertainty in estimates of GHG emissions and gross margins under climate change. METHODSAPSIM was used to simulate the effects of three crop residue retention rates (10%, 50% and 100%), and six representative crop rotations (wheat-canola, wheat-field pea-wheat-canola, wheat-field pea-wheat-oats, wheat-wheat-barley, wheat-wheat-canola, and wheat-wheat-oats) under two Shared Socio-economic Pathways scenarios (SSP245 and SSP585) using climate projections from 27 GCMs. GHG emissions and gross margins from 1961 to 2092 were assessed across 204 study sites in southeastern Australia. RESULTS AND CONCLUSIONSOur results showed that residue retention can turn the soil from a carbon source (10% retention, 304–450 kg CO2-eq ha−1 yr−1) to a carbon sink (100% retention, −269 ∼ −57 kg CO2-eq ha−1 yr−1), and the potential of carbon sequestration was partly offset by concomitantly increased N2O emissions. The wheat-wheat-canola rotation with full residue retention was shown to be a win-win solution with both large potential of GHG abatement and high gross margin compared with other rotations. Spatial analysis showed that the southeastern part of the study region, with higher rainfall, had higher gross margins, while the drier northwestern part had greater GHG emission reduction potentials. Although climate change led to increased GHG emissions and decreased yields for some crops, these adverse effects were overweighed by the higher SOC and yield advantages from full residue retention. SIGNIFICANCEThis study emphasizes the significant potential for agronomic management to maximize gross margin and reduce GHG emissions under climate change in southeast Australia. Results from this study could be used by farmers and policymakers to mitigate climate change without compromising agroecosystem profitability.

Impact of Cultivation Practices and Varieties on Productivity, Profitability, and Nutrient Uptake of Rice (Oryza sativa L.) and Wheat (Triticum aestivum L.) Cropping System in India

Interest in conservation measures, including reduced tillage, zero tillage, and crop residue retention, is growing in major rice growing areas of the world; particularly in the Indo-Gangetic plains. Of late, research interest is increasing in India for a specialised method of cultivation known as natural farming, which aims at maintain the functional biodiversity of the farm with little or no use of external inputs. With the increasing water crisis at a global level, it became imperative to develop technologies that can reduce the water use, particularly in water-guzzling low land paddy, by developing alternate cultivation methods; direct seeded rice is one such technology. A two-year field experiment was carried out at two locations during 2019–2020 and 2020–2021 to find out the impact of different cultivation and varieties on the productivity and profitability of the rice–wheat cropping system. The experiments were conducted in split plot design, replicated thrice, with cultivation practices in the main plot and varieties of both wheat and rice in the sub plot. The results so obtained reveal that conventional tillage significantly out yielded other methods of cultivation in both the crops at both the locations, while significantly lower grain yield in both crops was observed from natural farming. Adoption of reduced tillage, zero tillage and natural farming reduced the grain yield of wheat by 4.6%, 10.9%, and 59.4% over conventional tillage, while the corresponding decline in grain yield of rice was 10.8%, 16.1%, and 34.0% with reduced tillage, zero tillage, and natural farming, respectively. Among the varieties tested, HPW 368 and Him Palam Lal Dhan 1 (HPR 2795) produced significantly higher grain yield of wheat and rice, respectively, at both the locations during both years. Conventional tillage among cultivation practices and HPW 368 and Him Palam Lal Dhan 1 (HPR 2795) among wheat and rice varieties also proved to be better in terms of various economic indicators, including gross return, net return, and ratio benefit cost ratio (B:C ratio).

Residue retention and nitrogen management of preceding crops influences the productivity, profitability and environmental footprints of summer mungbean in maize-based cropping systems under conservation agriculture

ABSTRACT A field study was carried out during 7th and 8th cycles in conservation agriculture to assess the influence of cropping system {(maize-mustard (MMu) and maize-wheat (MW)}, residue application {(with residue (WR) and without residue (WoR)} and precision nitrogen management options in preceding crop {recommended dose of N (RDN), 33%, 50% and 70% basal RDN + green seeker (GS) based N application} on succeeding summer mungbean. The WR enhanced 17.5% and 13.6% seed yield with 29.1% and 12.06% higher net returns of mungbean in MMu and MW, respectively. Residue mulching with 50+ GS significantly increased the seed protein content. The MMu with WR and 33+ GS produced higher environmental footprints (532.8 and 479.5 kg CO2-e Mg−1), respectively. Similarly, significantly higher gross energy was produced in WR (44.2 × 103 MJ ha−1) while, WoR produced higher net energy (11.7 × 103 MJ ha−1) under MMu compared to MW (43.1 and 8.31 MJ ha−1), respectively. Thus, growing of mungbean under maize-based cropping systems with residue and 50+ GS guided N fertilization to previous crops (maize-wheat/mustard) improved yield and net returns with lower environmentally footprints and energy consumption in Indo-Gangetic plains (IGP) and similar agro-ecologies.

Conservation tillage and residue management improve soil health and crop productivity—Evidence from a rice-maize cropping system in Bangladesh

The rice-maize (R-M) system is rapidly expanding in Bangladesh due to its greater suitability for diverse soil types and environments. The present conventional method of cultivating puddled transplanted rice and maize is input-intensive, decreases soil health through intense ploughing, and ultimately reduces farm profitability. There is a need to investigate alternatives. Accordingly, we conducted a replicated 2-year (2020–2021) field study to investigate the effects of conservation agriculture (CA) based tillage and crop establishment (TCE) techniques and residue management practices on the physical, chemical, and biological properties of soil along with crop productivity and the profitability of rice-maize systems in the sandy loam soil of Northwest Bangladesh. Two TCE techniques Puddled transplanted rice (PTR) followed by Conventional tillage maize (CTM) and strip tillage direct-seeded rice (STDSR) followed by strip-tilled maize (STM) were assigned to the main plots and different percentages of crop residue retention (0, 25, and 50% by height) were allocated to the subplots. Results showed that a reduction in bulk density (BD), soil penetration resistance (SPR), and increased soil porosity were associated with STDSR/STM-based scenarios (strip tillage coupled with 25 and 50% residue retention). The soil organic carbon (SOC) fractions, such as dissolved organic C (DOC), light and heavy particulate organic matter C (POM-C), MAOM, and microbial biomass C (MBC) levels in the 0–10 cm layer under ST based treatments were 95, 8, 6, 2 and 45% greater, respectively, compared to CT with no residue treatment. When compared to the CT treatment, the DOC, light POM-C, heavy POM-C, and MAOM in the 10–20 cm layer with ST treatment were 8, 34, 25, 4 and 37% higher, respectively. Residue retention in ST increased average rice, maize, and system yields by 9.2, 14.0, and 14.12%, respectively, when compared to CT. The system gross margin and benefit-cost ratio (BCR) were $1,515 ha−1 and 1.90 under conventional tillage to $1,696 ha−1 and 2.15 under strip-tillage practices. Thus, our study suggests that CA could be an appropriate practice for sustaining soil fertility and crop yield under R-M systems in light-textured soils or other similar soils in Bangladesh.

Improving Resource Utilization Efficiency and Productivity in Rice-wheat Cropping System through Cutting Edge Technologies: An Overview

Rice-wheat cropping system is one of the major cropping system practiced in South Asia on 13.5 m hectares area, 10.3 million hectares of which are in the Indo-Gangetic Plains (IGP). The Indian Rice-Wheat Cropping System (RWCS) accounts for more than 70% of the country’s total grain production which is essential for ensuring national food security. Widely used RCT known as Zero Tillage (ZT) in which wheat is directly sown into the undisturbed soil after rice harvested. The Adoption of Furrow Irrigated Raised Bed System (FIRBS) in wheat production saves 30-40% water, seed use by 25-30% and nutrients use by 25% without reducing yield. The RCTs involve residue management (mainly residue retention), crop diversification and no- or minimum tillage with direct seeding and bed planting. AWD in rice save water by 10 to 30% while reducing seepage and deep drainage losses and Brown manuring is highly beneficial for weed control, water and soil conservation and nutrient supplementation. The cultivation of aerobic rice is a new system of growing in non-flooded, non-puddled soils, with high external inputs using innovative technique of aerobic rice that require less water than transplanted rice. A simple and inexpensive diagnostic tool leaf colour chart can be used for monitoring the relative greenness as a measure of the plant N status. Thus, it can be concluded that RCT adoption improving soil health, water use efficiency and nutrient use efficiency with higher sustained yields which leads to sustainable improvements in RWCS. By saving on labour, time, diesel, fertilisers, pesticides, and farm power, resource conservation technologies lower the cost of farming and also lessen environmental pollution.

Effect of Integrated crop management and blackgram (Vigna mungo) intercropping in maize (Zea mays)

A 2 year field experiment was conducted during rainy (kharif) seasons of 2019 and 2020 to investigate the influence of integrated crop management (ICM) modules and blackgram (Vigna mungo L.) intercropping on crop growth, productivity and crop efficiencies in maize (Zea mays L.). The maize crop under ICM7 [zero-tillage (ZT) + permanent raised-beds (PRB) + crop residue retention (3 t/ha) + 100% RDF + glyphosate pre-planting (PP) followed by (fb) pendimethalin pre-emergence (PE) fb tembotrione post-emergence (POE) application + 3 irrigations + need-based integrated crop protection] module intercropped with blackgram showed significantly higher plant height, dry matter accumulation (174.2 g/plant), crop growth rate (20.8 g/m2/day), relative growth rate (115 mg/g/day), average grain (6.17 t/ha), and stover yield (8.2 t/ha) and average crop efficiencies like production (60.2 kg/ha/day), monetary-efficiency (795.5 `/ha/day) and irrigation water productivity (4 kg/m3) over conventional-till and organic module in both study years. Overall, conservation agriculture (CA)-based module involving zero-tillage on PRB, crop residue retention, 100% RDF, glyphosate-PP, pendimethalin-PE and tembotrione-POE with 3-irrigations and other need-based plant protection measures with blackgram intercropping improved growth, yield and crop efficiencies of maize under maize + blackgram-wheat cropping system.

Effects of Conservation Tillage and Weed Management On Soil Microbial Community and Enzymatic Activity

Conservation tillage and weed management practices were applied on maize-wheat cropping system to study the soil biological activities under Northern Himalayas region. The experiment included five tillage and three weed management treatments. Conservation agriculture (CA)-based management practices including residues incorporation (ZTR-ZTR), ZT-ZT, and ZT-ZTR showed higher soil microbial population (bacteria, fungi, and actinomycetes) and microbial activity during 2014-15 and 2015-16 in both maize and wheat crop as compared to conventional tillage (CT-CT). Among different weed management practices, IWM-IWM showed the highest microbial communities population and microbial activities as compared to the application of herbicides and weedy check. Results clearly exhibited that CA with all three proven principles (no-tillage, residue retention, and crop diversification) in the maize-wheat system along with intercrop resulted in higher microbial activities, and population compared to other conventional management systems. Bangladesh J. Bot. 51(3): 425-431, 2022 (September)

Long-term conservation agriculture increases nitrogen use efficiency by crops, land equivalent ratio and soil carbon stock in a subtropical rice-based cropping system

Conservation Agriculture (CA) is still a relatively new approach for intensively cultivated (3 crops yr -1 ) rice-based cropping systems that produce high crop yield and amounts of residues annually. With the recent development of transplanting of rice into tilled strips on non-puddled soil, CA could become feasible for rice-based cropping patterns. However, the effect of increased retention of crop residues on crop response to nitrogen (N) fertilization rate in strip tilled systems with the transplanted rice and other crops grown in the annual rotation is yet to be determined. For nine years, we have examined the effects of soil disturbance levels - strip tillage (ST) and conventional tillage (CT), two residue retention levels –15% residue by height (low residue, LR) and 30% residue (high residue, HR) and five N rates (60%, 80%, 100%, 120%, and 140% of the recommended N fertilizer doses (RFD)) for a rice-wheat-mungbean cropping sequence. The 100% RFD was 75, 100 and 20 kg N ha -1 for rice, wheat, and mungbean, respectively. Rice yields were comparable between the two tillage systems for up to year-6, wheat for up to year-3 but mungbean yield markedly increased in ST from year-1; however, the land equivalent ratio increased from year-1, principally because of higher mungbean yield. Introduction of ST increased land equivalent ratio by 26% relative to CT, N use efficiency and partial factor productivity. Nitrogen fertilizer demand for maximum yield in ST was increased by about 10% for rice and 5% for mungbean but decreased by 5% for wheat. Although fertilizer N demand had increased in ST system due to higher yield than CT, the N requirement declined by50–90% when the same yield goal is considered for ST as for CT. The soil organic carbon stock (0–15 cm) after 8 years increased from 21.5 to 30.5 t ha -1 due to the effect of ST plus high crop residue retention. Annual gross margin increased by 57% in ST over CT practice and 26% in HR over LR retention. In conclusion, after 9 years practicing CA with increased residue retention under strip tillage, the crops had higher N use efficiency, grain yield, land equivalent ratio and annual gross margin in the rice-wheat-mungbean cropping system while the N fertilizer requirement increased minimally. • Strip tillage (ST) with residue retention increased crop profitability. • Adoption of ST practice increased N use efficiency. • The ST practice required about 10% more N but produced higher rice crop yield. • Strip tillage plus residue retention increased SOC stock by 9 t ha -1 over 8 years.

Interpretable machine learning methods to explain on-farm yield variability of high productivity wheat in Northwest India

The increasing availability of complex, geo-referenced on-farm data demands analytical frameworks that can guide crop management recommendations. Recent developments in interpretable machine learning techniques offer opportunities to use these methods in agronomic studies. Our objectives were two-fold: (1) to assess the performance of different machine learning methods to explain on-farm wheat yield variability in the Northwestern Indo-Gangetic Plains of India, and (2) to identify the most important drivers and interactions explaining wheat yield variability. A suite of fine-tuned machine learning models (ridge and lasso regression, classification and regression trees, k-nearest neighbor, support vector machines, gradient boosting, extreme gradient boosting, and random forest) were statistically compared using the R 2 , root mean square error (RMSE), and mean absolute error (MAE). The best performing model was again fine-tuned using a grid search approach for the bias-variance trade-off. Three post-hoc model agnostic techniques were used to interpret the best performing model: variable importance (a variable was considered “important” if shuffling its values increased or decreased the model error considerably), interaction strength (based on Friedman’s H-statistic), and two-way interaction (i.e., how much of the total variability in wheat yield was explained by a particular two-way interaction). Model outputs were compared against empirical data to contextualize results and provide a blueprint for future analysis in other production systems. Tree-based and decision boundary-based methods outperformed regression-based methods in explaining wheat yield variability. Random forest was the best performing method in terms of goodness-of-fit and model precision and accuracy with RMSE, MAE, and R 2 ranging between 367 and 470 kg ha −1 , 276–345 kg ha −1 , and 0.44–0.63, respectively. Random forest was then used for selection of important variables and interactions. The most important management variables explaining wheat yield variability were nitrogen application rate and crop residue management, whereas the average of monthly cumulative solar radiation during February and March (coinciding with reproductive phase of wheat) was the most important biophysical variable. The effect size of these variables on wheat yield ranged between 227 kg ha −1 for nitrogen application rate to 372 kg ha −1 for cumulative solar radiation during February and March. The effect of important interactions on wheat yield was detected in the data namely the interaction between crop residue management and disease management and, nitrogen application rate and seeding rate. For instance, farmers’ fields with moderate disease incidence yielded 750 kg ha −1 less when crop residues were removed than when crop residues were retained. Similarly, wheat yield response to residue retention was higher under low seed and N application rates. As an inductive research approach, the appropriate application of interpretable machine learning methods can be used to extract agronomically actionable information from large-scale farmer field data. • Data-driven agronomic research requires new analytical and methodological approaches. • Machine learning methods were used to disentangle complex relationships in farmer field data. • Model-agnostic tools were used to derive agronomic interpretations. • Residue management and N application rate were important management variables for wheat yield. • Residue management interacted with other practices to explain wheat yield variability.

Land management and crop cover effect on soil erosion in the humid lowlands of Beles River Sub-Basin, North-Western Ethiopia

<p>Soil erosion is the most devastating environmental crisis in Ethiopia where the loss of soil from cultivated land is almost seven times the tolerable limit; specifically, Nitisol is very susceptible to erosion. To investigate the response of land management and cropping practices on sediment loss, a field experiment was conducted under natural environment on Nitisol of Pawi area. Nine treatments combining two tillage methods (zero and conventional), four crop covers (continuous maize, continuous soya bean, rotated maize, and maize soya bean intercrop), and continuous bare fallow as control were laid out in a randomized complete block design (RCBD) with three replications. The result showed that land management and crop cover significantly affect soil loss. Cultivation of crops without soil disturbance with full residue retention reduced soil loss by 6%, 36%, 36%, and 44% under soya bean, rotated maize, maize soya bean intercropping, and maize, respectively. Similarly, maize crop reduces soil loss by 34% under zero tillage management. Compared with conventionally managed maize crops, sediment concentration was also reduced by 14%, 17%, and 31%, maize with zero tillage, rotated maize with zero tillage, and maize soya bean intercropping with zero tillage, respectively. Except for zero-tilled maize soya bean intercropping and rotated maize, the seasonal soil loss was above the tolerable soil loss level of Ethiopia (2-10 t ha<sup>-</sup><sup>1</sup>). This indicates there is a need for other management practices like physical and agronomic soil conservation methods to lower soil loss rates below the tolerable limit. Generally, zero tillage with greater crop cover is an appropriate approach to reduce soil loss by improving soil hydrological properties without negatively affecting grain yield. To understand and quantify the long-term impact of tillage and crop cover on soil health and productivity in Ethiopia long-term study is needed as this study was based on one-year data from four years of permanent plots.</p>

Evaluation of aggregate stability methods for soil health

Aggregate stability is a commonly used indicator of soil health because improvements in aggregate stability are related to reduced erodibility and improved soil–water dynamics. During the past 80 to 90 years, numerous methods have been developed to assess aggregate stability. Limited comparisons among the methods have resulted in varied magnitudes of response to soil health management practices and varied influences of inherent soil properties and climate. It is not clear whether selection of a specific method creates any advantage to the investigator. This study assessed four commonly used methods of measuring aggregate stability using data collected as part of the North American Project to Evaluate Soil Health Measurements. The methods included water stable aggregates using the Cornell Rainfall Simulator (WSACASH), wet sieved water stable aggregates (WSAARS), slaking captured and adapted from SLAKES smart-phone image recognition software (STAB10), andthemean weight diameter of water stable aggregates (MWD).Influence of climate and inherent soil properties at the continental scale were analyzed in addition to method responses to rotation diversity, cash crop count, residue management, organic nutrient amendments, cover crops, and tillage. The four methods were moderately correlated with each other. All methods were sensitive to differences in climate and inherent soil properties between sites, although to different degrees. None measured significant effects from rotation diversity or crop count, but all methods detected significant increases in aggregate stability resulting from reduced tillage. Significant increases or positive trends were observed for all methods in relation to cover cropping, increased residue retention, and organic amendments, except for STAB10, which expressed a slightly negative response to organic amendments. Considering these results, no single method was clearly superior and all four are viable options for measuring aggregate stability. Therefore, secondary considerations (e.g., cost, method availability, increased sensitivity to a specific management practice, or minimal within-treatment variability) driven by the needs of the investigator, should determine the most suitable method.

Double zero-tillage and foliar-P nutrition coupled with bio-inoculants enhance physiological photosynthetic characteristics and resilience to nutritional and environmental stresses in maize-wheat rotation.

Conventionally tilled maize–wheat cropping system (MWCS) is an emerging cereal production system in semi-arid region of south-Asia. This system involves excessive tillage operations that result in numerous resource- and production-vulnerabilities besides impeding environmental-stresses. Likewise, phosphorus is a vital nutrient that limits crop growth and development. It’s a matter of great concern when ∼80% of Indian soils are low to medium in available-P due to its sparing solubility, resulting in crop stress and low yields. Hence, crop productivity, photosynthetic parameters and resilience to nutritional and environmental stresses were assessed in a MWCS using four crop-establishment and tillage management (CETM) practices [FBCT-FBCT (Flat bed-conventional tillage both in maize and wheat); RBCT-RBZT (Raised bed-CT in maize and raised bed-zero tillage in wheat); FBZT-FBZT (FBZT both in maize and wheat); PRBZT-PRBZT (Permanent raised bed-ZT both in maize and wheat)], and five P-fertilization practices [P100 (100% soil applied-P); P50+2FSP (50% soil applied-P + 2 foliar-sprays of P through 2% DAP both in maize and wheat); P50+PSB+AM-fungi; P50+PSB+AMF+2FSP; and P0 (100% NK with no-P)] in split-plot design replicated-thrice. The results indicated that double zero-tilled PRBZT–PRBZT system significantly enhanced the grain yield (6.1; 5.4 t ha–1), net photosynthetic rate (Pn) (41.68; 23.33 μ mol CO2 m–2 s–1), stomatal conductance (SC) (0.44; 0.26 mol H2O m–2 s–1), relative water content (RWC) (83.3; 77.8%), and radiation-use efficiency (RUE) (2.9; 2.36 g MJ–1) by 12.8–15.8 and 8.5–44.4% in maize and wheat crops, respectively over conventional tilled FBCT–FBCT. P50+PSB+AMF+2FSP conjugating soil applied-P, microbial-inoculants and foliar-P, had significantly higher Pn, SC, RUE and RWC over P100 besides saving ∼34.7% fertilizer-P under MWCS. P50+PSB+AMF+2FSP practice also had higher NDVI, PAR, transpiration efficiency and PHI over P100. Whereas lower stomatal limitation index (Ls) was observed under PRBZT–PRBZT system as compared to the conventional FBCT–FBCT system indicating that P is the limiting factor but not stomata. Hence, optimum P supply through foliar P-fertilization along with other sources resulted in higher grain yield by 21.4% over control. Overall, double zero-tilled PRBZT–PRBZT with crop residue retention at 6 t/ha per year, as well as P50+PSB+AMF+2FSP in MWCS, may prove beneficial in enhancing the crop productivity and, thereby, bolstering food security in semi-arid south-Asia region.

Soil Autotrophic Bacterial Community Structure and Carbon Utilization Are Regulated by Soil Disturbance—The Case of a 19-Year Field Study

The roles of bacterial communities in the health of soil microenvironments can be more adequately defined through longer-term soil management options. Carbon dioxide (CO2) fixation by autotrophic bacteria is a principal factor in soil carbon cycles. However, the information is limited to how conservation tillage practices alter soil physiochemical properties, autotrophic bacterial communities, and microbial catabolic diversity. In this study, we determined the changes in autotrophic bacterial communities and carbon substrate utilization in response to different soil management practices. A replicated field study was established in 2001, with the following soil treatments arranged in a randomized complete block: conventional tillage with crop residue removed (T), conventional tillage with residue incorporated into the soil (TS), no tillage with crop residue removed (NT), and no tillage with residue remaining on the soil surface (NTS). Soils were sampled in 2019 and microbial DNA was analyzed using high-throughput sequencing. After the 19-year (2001–2019) treatments, the soils with conservation tillage (NTS and NT) increased the soil’s microbial biomass carbon by 13%, organic carbon by 5%, and total nitrogen by 16% compared to conventional tillage (T and TS). The NTS treatment increased the abundance of the cbbL gene by 53% in the soil compared with the other soil treatments. The cbbL-carrying bacterial community was mainly affiliated with the phylum Proteobacteria and Actinobacteria, accounting for 56–85% of the community. Retaining crop residue in the field (NTS and TS) enhanced community-level physiological profiles by 31% and carbon substrate utilization by 32% compared to those without residue retention (T and NT). The 19 years of soil management lead to the conclusion that minimal soil disturbance, coupled with crop residue retention, shaped autotrophic bacterial phylogenetics, modified soil physicochemical properties, and created a microenvironment that favored CO2-fixing activity and increased soil productivity.

Soil quality restoration and yield stabilization in acidic soils of northeastern Himalayas: Five years impact of green manuring and crop residue management

Soil quality restoration and crop productivity maximization are the global challenge to feed the galloping population. The task is much more daunting in a risk-prone, fragile, and low productive hilly region due to the depletion of supporting and regulating ecosystem services. A five-year long-term (2012–2017) field experiment was conducted to stabilize the yield and soil quality through legume green manuring and crop residue recycling in intensified cropping systems in the Eastern Himalayan region of India. Four treatments involving three green manures [green gram (Vigna radiata); cowpea (Vigna unguiculata);Sesbania(Sesbania aculeata) along with control (no-green manure)], three cropping systems [groundnut (Arachis hypogaea)—pea (Pisum sativum); maize (Zea mays)—pea, and maize + groundnut–pea] and two levels of residue management practices [residue removal and residue retention] were evaluated in three times replicated split–split plot design. Among the green manure options,Sesbaniaexerted a significant positive impact on the soil organic carbon (SOC) stock, available micro- (Fe, Mn, Zn, and Cu), and macronutrients (N, P and K) in surface (0–0.15 m) and subsurface (0.15–0.45 m) soils. The improvement in soil enzymatic activities (acid phosphatase, alkaline phosphatase, dehydrogenase, beta-glucosidase, and aryl sulfatase activity) (p< 0.05) inSesbania-treated soil was +28.1% to +38.9% in surface and +18.3% to +27.3% in subsurface soils over non-green manure.Sesbania-treated soils also exhibited higher soil quality index (SQI) and stratification ratio (SR) of available soil nutrients and enzymes over non-green manured soils. Among the cropping systems, groundnut intercropped with maize followed by peas (MGP) within situresidue retention increased (p< 0.05) the available soil macro- and micronutrients, SOC stock, soil enzymes, SR, and SQI in comparison to other cropping systems.Sesbaniagreen manuring and residue retention improved the yield sustainability by +19% and +11% in the MGP system over non-green manuring and residue removal, respectively. Therefore,Sesbaniagreen manuring in the MGP cropping system along with residue retention is recommended for stabilizing the soil quality through enhancing supporting and regulating ecosystem services and maintaining long-term productivity in the fragile Eastern Himalayan ecosystem of India.

Sustainable Intensification of Rice Fallows with Oilseeds and Pulses: Effects on Soil Aggregation, Organic Carbon Dynamics, and Crop Productivity in Eastern Indo-Gangetic Plains

Climate-smart agriculture (CSA) practices are becoming increasingly important due to their better adaptability to harsh climatic conditions (in general) and the unpredictability of monsoons in India (in particular). Conventional rice cultivation (e.g., PTR) involves intensive tilling followed by intensive puddling in standing water that destroys the soil aggregation and depletes carbon pools. Therefore, alternative crop establishment methods need to be devised for the sustainability of system productivity, and the suitabilities of potential oilseeds and pulses need to be tested for cropping intensification in rice-fallow regions. Hence, an ongoing experiment (implemented in 2016) was evaluated to identify the appropriate CSA management practices in restoring soil C and physical health under diversified cropping systems in the rice-fallow system of eastern India. Six tillage and crop establishment methods along with residue management were kept as the main plots [zero-till-direct-seeded rice (ZTDSR), conventional-till-DSR (CT-DSR), puddled transplanted rice (PTR), ZTDSR with rice residue retentions (ZTDSRR+), CTDSR with rice residue retention (CTDSRR+), PTR with rice residue retention (PTRR+)] while five winter/post-rainy crops (oilseeds and pulses) were raised in a subplot. In the ZTDSRR+ production system, soil macro-aggregate (%), macro-aggregate-associated C, MWD, and GMD of aggregates increased by 60.1, 71.3, 42.1, and 17.1%, respectively, in comparison to conventional tillage practices (PTR). The carbon management index (CMI) was 58% more in the ZTDSRR+ production system compared to PTR. Among the winter crops, chickpeas recorded higher values of soil structural indices and C content. In the PTR production system, system productivity, in terms of rice equivalent yield, was comparable to ZTDSRR+. ZT with residue retention in rice followed by post-rainy/winter pulses led to higher C content and structural stability of the soil. Thus, CSA management practices can improve the crop productivity as well as soil health of rice-fallow production systems of eastern India and comparable agroecotypes of South Asia.

Impact of Long-Term Conservation Agriculture Practices on Phosphorus Dynamics under Maize-Based Cropping Systems in a Sub-Tropical Soil

Over the past decade, scientific studies have increasingly concentrated on the effects of global phosphorus (P) scarcity on food security. A comprehensive strategy that considers demand reduction and recycling possibilities is needed to address the global P scarcity. Reduced tillage along with crop residue retention could decrease fixation of P in soil, improve labile P content and enhance organic-P (Po) buildup and its mineralization by phosphatases; this could be an extra benefit of conservation agriculture (CA) in soils. To study the impact of long-term CA on soil organic and inorganic P fractions and their distribution, a long-term field trial was conducted under a maize-based cropping system with different tillage (zero tillage (ZT), permanent bed (PB) and conventional till (CT) and cropping system (maize–wheat–mungbean (MWMb), maize–chickpea–sesbania (MCS), maize–mustard–mungbean (MMuMb) and maize–maize–sesbania (MMS)). Phosphorus dynamics were studied through sequential fractionation (organic and inorganic P) at 0–5 and 5–15 cm soil depth. The findings showed that a higher amount of soluble and loosely bound P (SL-P) was detected in ZT among the inorganic P fractions, whereas iron-bound P (Fe-P), aluminum-bound P (Al-P), reductant soluble P (RES-P) and calcium-bound P (Ca-P) were found higher in CT in both soil depths. Among Organic-P fractions, moderately labile and non-labile Po was found higher in PB and ZT but, in the case of labile Po, it was found insignificant with respect to tillage operations. Significant synergistic effects of winter legume (chickpea) with summer legumes (sesbania and mungbean) in crop rotation were observed on SL-P, Labile Po, Humic acid-Po, Alkaline phosphatase and MBP at 0–5 and 5–15 cm soil depths. Given the potential relevance of understanding P dynamics for efficient P management in long-term conservation agriculture practices, our findings offers critical new insight for the P management for sustainable development.

Long‐term no‐tillage and rye cover crops affect soil biological indicators on Andosols in a humid, subtropical climate

AbstractThe effects of tillage and cover crop management on the physical and chemical properties of soil are well‐documented. However, the responses of soil microbes to long‐term tillage and crop rotation schemes still need clarification. The objective of this study was to determine the effects of different tillage and cover crop systems on soil biological indicators and their interactions in Andosols in a humid subtropical climate in Japan. This study was conducted during a field trial established in 2002. The main factors were tillage systems (no‐tillage [NT] and mouldboard ploughing [MP]); the subplot was winter cover crop treatments (bare fallow [FA] and rye [RY]) succeeding summer soya bean. Soil microbial biomass, community and structure, and soil organic carbon (SOC) stock were assessed, as well as soil respiration in the past 2.5 years. Overall, the NT and RY systems increased the soil respiration and SOC stocks relative to those detected in the MP and FA systems. After being differentiated for 18 years, the tillage systems showed a greater influence on the soil microbial community and biomass than cover crop treatments. These tillage systems significantly altered the bacterial alpha diversity (NT > MP) and soil microbial biomasses (NT > MP) based on soil Adenosine 5′‐triphosphate content, substrate‐induced respiration and ergosterol content. The NT and RY treatments stimulated soil respiration by positively affecting plant residue retention, SOC stocks, bacterial alpha diversity, soil microbial biomass in summer, and the relative abundance of organic matter decomposers, such as Bacteroidetes‐, Basidiomycota‐ and Ascomycota‐related species. These results suggest that the NT and RY systems helped improve the soil microbial properties of Andosols in a humid subtropical climate in Japan. However, their potential vulnerability to SOC sequestration due to elevated soil respiration needs further clarification, especially in the context of global warming.Highlights Soil microbe responses to agricultural measures on Andosols were studied. No‐tillage and rye cover crops stimulated soil respiration. No‐tillage shifted the soil microbial community more than cover crops. No‐tillage improved the soil organic carbon stock and bacterial alpha diversity.

Effect of vegetable residues incorporation on soil fertility, rhizosphere microbial community structure, and plant growth of continuously cropped cucumber in a solar greenhouse

PurposeIncorporating crop residues into the soil is considered a sustainable and valuable method to alleviate soil deterioration caused by continuous monoculture in greenhouse production. However, the effect of vegetable residues retention on soil amendments is poorly understood. In the present study, we investigated the impacts of sweet pepper, tomato, and cucumber plant residues on soil microbial communities and plant growth of continuously cropped cucumber in a solar greenhouse.MethodsThe 16S rRNA and ITS1 rRNA genes were amplified, and high-throughput sequencing was performed to explore the impacts of vegetable residues incorporation on soil microbial communities. Additionally, soil chemical properties, cucumber root vigor, and fruit yield were measured to assess the impacts of vegetable residues incorporation on continuously cropped soil and cucumber growth.ResultsThe results showed that incorporating vegetable residues could improve soil buffering capacity, increase the content of soil organic matter and available nutrients, and increased the diversity of soil microorganisms and improved community structure; vegetable residues increased the abundance of beneficial bacteria such as Actinobacteria, Firmicutes, Proteobacteria, and Chloroflexi, while reducing the quantity of soil-borne pathogens such as Bacillariophyta and Acidobacteria. Similar results were observed for the fungal communities: the relative abundance of Ascomycota was decreased to varying degrees, while the relative abundance of Rozellomycota and Basidiomycota was raised. The results demonstrated that vegetable residues incorporation significantly increased cucumber root vigor and enhanced fruit yield. The effects of different types of residues on improving soil properties were ordered sweet pepper plant residues > cucumber plant residues > tomato plant residues, and 20% of sweet pepper plant residues incorporation had the most significant effect on crop yield.ConclusionIn summary, returning vegetable residues alleviated soil continuous cropping obstacles by improving the soil fertility and the diversity and community structure of soil microorganisms, and consequently promoting the growth and yield of greenhouse-grown cucumbers. The findings demonstrated that returning vegetable residues was an effective and sustainable measure for soil amendment during continuous cropping in greenhouse production.

Contribution of wheat and maize to soil organic carbon in a wheat‐maize cropping system: A field and laboratory study

Abstract Retention of crop biomass is widely recommended to improve soil organic carbon (SOC). However, the magnitude of contribution of above‐ground residues and below‐ground roots from C3 and C4 crops to SOC is unclear. Data from a 10‐year field experiment and a 60‐day laboratory incubation were synthesized to identify the respective contribution of C3 (e.g., wheat) and C4 (e.g., maize) residues and roots to SOC, as well as its underlying mechanisms under no‐till (NT) using 13C labelling trace in wheat‐maize rotations. The field experiment showed that residue retention significantly increased SOC accumulation, and SOC derived from wheat was 126.0% higher than that from maize. Conversion to NT promoted SOC derived from wheat and thus accumulated 17.6% higher SOC stock compared with plough tillage (PT) under residue returning at 0–20 cm soil depth (p < 0.05). The data from laboratory incubation revealed the mechanisms that lower priming effects at 0–10 cm depth decreased total mineralization by 91.8% after inputs of wheat residues and roots compared with that of maize residues and roots, especially under NT compared with PT. Priming effects were negatively correlated with enzyme activities associated with the C recycle, SOC, and total nitrogen (TN) contents (p < 0.01). NT increased enzyme activities, SOC, and TN contents and thus reduced priming effects and improved residual carbon. Synthesis and applications. These results suggested that wheat may contribute more to SOC accumulation than maize, and carbon increment efficiency in farmland could be enhanced by considering the crucial roles of C3 crops in SOC accumulation. NT practice sustains the benefits of C3 crops to SOC sequestration in the upper soil depths.