Wheat-maize Cropping System Research Articles

Lowering carbon footprint of wheat-maize cropping system in North China Plain: Through microbial fertilizer application with adaptive tillage

Optimization of fertilizer and tillage management in agroecosystems can be an effective strategy to reduce greenhouse gas (GHG) emission and improve carbon sequestration. Using a system boundary that started at winter wheat seeding and ended at summer maize harvest, a field experiment was conducted in Shandong Province (North China) to determine the effect of microbial fertilization and tillage on the carbon footprint (CF). The climate-based ecosystem services were evaluated in wheat-maize cropping systems. Also the optimal microbial fertilization and tillage with the lowest CF, highest climate-based ecosystem services and highest crop yield were determined. The results showed that compared with microbial organic fertilization, the use of microbial decomposing agents increased soil organic carbon (SOC) sequestration (2582.1–2909.9 kg CO2-eq ha−1 yr−1) and reduced CF (0.11–0.12 kg CO2-eq kg−1 grain). Chemical fertilization was the largest contributor to total CF (27.5–56.7%), which decreased with decreasing chemical fertilization. Climate-based ecosystem services of microbial fertilization with rotary tillage (1689.9–1795.6 US$ ha−1 yr−1) were significantly higher than those of chemical fertilization. In the limited system boundary of wheat-maize cropping, microbial decomposing agent MA (of 30 L ha−1) with rotary tillage had the highest grain production, GHG emission mitigation and climate-based ecosystem services enhancement.

Crop yield and N2O emission affected by long-term organic manure substitution fertilizer under winter wheat-summer maize cropping system

Application of organic manure combined with synthetic fertilizer can maintain crop yield and improve soil fertility, but the long-term effects of substituting different proportions of synthetic fertilizers with organic manure on N2O emission remain unclear. In this study, field experiments and DNDC model simulations were used to study the long-term effects of substituting synthetic fertilizers with organic manure on crop yield and N2O emission. The field experiment was conducted at Guanzhong Plain, northern China, under a wheat-maize cropping system. Six treatments were included: no fertilization (CK); synthetic nitrogen (N), phosphorus (P) and potassium (K) fertilizers (NPK); and 25%, 50%, 75% and 100% of the synthetic N substituted by dairy manure (25%M, 50%M, 75%M, and 100%M), respectively. The DNDC model was calibrated using the field data from the NPK treatment from 2014 to 2017 and was validated for the other treatments. The results showed that the DNDC model can successfully simulate the crop yield (e.g. nRMSE < 5%) and annual N2O emission (nRMSE < 20%). In addition, a 30-year simulation found that organic manure substitution treatments could maintain wheat yield well, and the yield variation between different years was small. However, relative to the NPK treatment, the maize yields for the first 6 and 7 years were lower under 50%M and 75%M, and under 100%M maize yields were reduced for the first 15 years. The long-term simulation showed that N2O emission of fertilized treatment had an increasing trend over time, especially the 75%M treatment where the N2O emission was higher than that of NPK treatment after 25 years of fertilization. The annual mean N2O emission under different treatments was, in decreasing order, NPK > 25%M > 50%M > 75%M > 100%M > CK. The yield-scale N2O emission and emission factor were highest for the NPK treatment. Considering crop yield, yield stability and N2O emission, substitution of 25% synthetic fertilizer by organic manure can simultaneously ensure crop productivity and environmental protection under the tested environment.

Characteristics of carbon mineralization and accumulation under long-term conservation tillage

Conservation tillage has been widely practiced to increase soil organic carbon (SOC), and reducing SOC mineralization has the potential to improve accumulation. To assess the effects of conservation tillage on characteristics of SOC mineralization and accumulation, as well as their relationship, a site experiment was established in 2008 using data from 2012 to 2019 under wheat-maize cropping system. Four treatments were investigated: no-till with straw retention (NTS, conservation tillage), no-till with straw removal (NT), conventional tillage with straw incorporation (CTS), conventional tillage with straw removal (CT). The results showed that NTS significantly improved SOC concentration than the other treatments at 0–10 cm soil depth (P < 0.05) by 5–18% in 2012 and 31–93% in 2019 (increasing increments over time). There was a negative correlation (R2 = -0.60) between SOC concentration and mineralizability. On average, the SOC mineralizability under NTS was 39.0 mg C kg−1 SOC at 0–10 cm depth, significantly lower than CTS and CT (P < 0.05). Furthermore, relative SOC mineralizability of NT/NTS, CTS/NTS, and CT/NTS was>1 and showed a linear relationship with time, indicating that NTS can increase SOC accumulation by reducing SOC mineralizability over time. A negative correlation was observed between SOC mineralizability and mean weight diameter (MWD) (R2 = -0.34), and the highest MWD under NTS, suggesting reduced mineralizability due to enhanced physical protection of soil macro-aggregates. Furthermore, the particulate organic carbon (POC) concentration was highly correlated with MWD (R2 = 0.76). Conclusively, results elucidated that higher POC under conservation tillage contributed to the macro-aggregate formation and aggregate stability at 0–10 cm depth, and thus protected SOC from mineralization, and additional SOC sequestration could be accelerated by improving the duration of conservation tillage.

Carbon Balance under Organic Amendments in the Wheat-Maize Cropping Systems of Sloppy Upland Soil

With an increasing interest in closing the nutrient loop in agroecosystems, organic amendments are highly recommended as a reliable resource for soil nutrient recycling. However, from a carbon sequestration perspective, not much has been reported on the contribution of different organic amendments to soil organic carbon (SOC), crop carbon (C) uptake, and soil carbon dioxide (CO2) emissions in wheat-maize cropping systems of sloppy upland soil. To fill the knowledge gap, a two-year lysimeter-field plots experiment was conducted in a sloppy upland purplish soil under wheat-maize cropping systems. The experiments were arranged in a complete random block design with five treatment plots, namely; fresh pig slurry as organic manure (OM), crop residues (CR), conventional mineral fertilizers (NPK) as the control, organic manure plus mineral fertilizers (OMNPK), and crop residues plus mineral fertilizers (CRNPK). Our results showed the leaf photosynthesis rate was not significantly increased by organic amendment application treatments compared to NPK treatment, and was within a range of 4.8 to 45.3 µmol m−2 s−1 for the wheat season and −20.1 to 40.4 µmol m−2 s−1 for the maize season across the five treatments and the measured growth stages. The soil CO2 emissions for the maize season (in the range of 203 to 362 g C m−2) were higher than for the wheat season (in the range of 118 to 252 g C m−2) on average across the different experimental treatments over the two-year experiment. The organic amendment application increased annual cumulative CO2 emissions from 30% to 51% compared to NPK treatment. Over the two years, the average crop C uptake ranged from 174 to 378 g C m−2 and from 287 to 488 g C m−2 for the wheat and maize seasons, respectively, and the organic amendment application increased the crop C uptake by 4% to 23% compared to NPK treatment. In the organic amendment treatments, the C balance ranged from −160 to 460 g C m−2 and from −301 to 334 g C m−2 for the wheat and the maize seasons, respectively, which were greater than those in the NPK treatment. Overall, the present study results suggest incorporation of organic amendments could be an effective strategy for increasing C sequestration and sustaining crop productivity in sloppy upland soil.

Conservation agriculture and nitrogen management in maize–wheat cropping system: effect on growth, productivity and economics of wheat

A study was conducted at ICAR-Indian Agricultural Research Institute, New Delhi to assess the effect of six combinations of tillage and crop establishment techniques, i.e. conventional tillage-flat-bed (CT-F), CT-raised-bed (CT-B), zero tillage-flat-bed with crop-residue (ZT-F+R) and without crop-residue (ZT-F), ZT-raised-bed with crop residue (ZT-B+R) and without crop-residue (ZT-B) in combination of four levels of fertilizer-nitrogen (N; 0, 60, 120 and 180 kg N/ha) on growth, yield and economics of wheat (Triticum aestivum L. emend. Fiori & Paol) in conservation agriculture based maize (Zea mays L.)-wheat cropping system. The performance of the wheat in terms of growth, yield and net returns was observed statistically similar under different tillage and establishment techniques but it was differed significantly (p ≤ 0.05) due to different levels of N. Crop-residue applied treatments (ZT-F+R/ZT-B+R) improved the grain and straw yields over without crop-residue applied ZT (by 5.2 and 3.6% under flat-planting; and 7.7 and 4.1% under raised-bed planting systems, respectively) and CT practices (by 12.0 and 5.4% under flat-planting and 8.1 and 3.4% under raised-bed planting systems, respectively). The ZT technology reduced the cost of cultivation by 9.8% and improved the net profits by 9.0% over the CT practices. Further, recycling of crop residue under ZT practices (ZT-F+R/ZT-B+R) not only produced the maximum grain yield (8.0-12.0% higher) but also generated either equal or higher net profits over the CT practices. The growth, yield attributes, grain yield, straw yield and net returns were increased significantly up to 120 kg N/ha, though the maximum values of most of these parameters were recorded at 180 kg N/ha. Therefore, it can be concluded that ZT practices along with crop residues and 120 kg N/ha could be adopted to make the wheat cultivation more remunerative and sustainable.

Long term effect of chemical fertilizers and amendments on chemical pools of nitrogen in maize-wheat cropping system in an acid Alfisol

The present investigation was carried out in the ongoing long term fertilizer experiment at Department of soil science, CSKHPKV Palampur. The influence of thirty six years of cropping with different chemical fertilizers and amendments on the contents and total N, inorganic N and organic N fractions at 0-0.15 m and 0.15-0.30 m depths was investigated in an Acid Alfisol. Continuous combined use of chemical fertilizers and FYM and manual weeding in 100% NPK treated plots resulted in significant increase in the soil organic carbon content compared to rest of the treatments. However, higher organic carbon content was recorded under surface soils. Continuous application of chemical fertilizers either alone or in combination with FYM or lime influenced different organic and inorganic nitrogen fractions significantly except non hydrolysable-N at both the depths. Hydrolysable ammonical-N was found to be the most dominant organic nitrogen fraction. Different organic and inorganic –N fractions at surface and subsurface soils were significantly and positively correlated with available N.

Wheat‐derived soil organic carbon accumulates more than its maize counterpart in a wheat–maize cropping system after 21 years

AbstractFertilization is the most common way to supply nutrients to the soil and to maintain crop productivity in agricultural ecosystems, which may also influence soil organic carbon (SOC) accumulation rates. In 1996, we set up a long‐term field experiment to explore the effect of fertilization on soil properties in a winter wheat–summer maize cropping system in the North China Plain. Eight treatments included: no fertilization (Ct), nitrogen (N), phosphorus (P) and N combined with P (NP) fertilizer application with or without potassium (K). After 21 years of fertilization, N application did not increase soil total N content, but P application significantly increased soil total P contents by 33.9%. The single application of N or P did not significantly affect SOC content, whereas the NP combination significantly increased SOC contents by 22.1 and 29.6% compared to Ct in the no K and K treatments, respectively. The natural 13C abundance approach and the SOC contents suggested that the NP combination increased C3 wheat‐derived SOC by 37.5 and 49.8% in the no K and K treatments, respectively. However, fertilization had no impact on C4 maize‐derived SOC content. Wheat‐derived SOC was positively correlated with the wheat yield, whereas maize‐derived SOC was not correlated with the maize yield, which indicated that wheat‐derived SOC accumulated more than maize‐derived SOC in the wheat–maize cropping system. In addition, soil inorganic carbon (SIC) and its compositions were not affected by the long‐term fertilization. Our results indicate that N combined with P application is more beneficial than N or P alone to enlarge SOC sequestration in the North China Plain, especially for wheat‐derived SOC. Thus, in soil with nutrient limitations, nutrient resources should be supplied with priority to the wheat growing season in wheat–maize cropping systems, to maintain or enlarge SOC storage.Highlights Long‐term N combined with P application increased wheat‐derived SOC Wheat‐derived SOC accumulated more than maize‐derived SOC in the cropping system Wheat yield was lower than maize in the wheat–maize cropping system Long‐term N, P or NP fertilization did not influence soil inorganic carbon

Effect of conservation agriculture and nitrogen management on root architecture and soil properties in maize-wheat cropping system

A field experiment was conducted to evaluate the effect of conservation agricultural and nitrogen management practices on root architecture and soil physical, chemical and biological properties after 2years of continuous maize-wheat cropping system. The experiment was carried out in split plot design with six main plot treatments of tillage and crop establishment techniques, i.e. conventional tillage-flat bed (CT-F), CT-raised bed (CT-B), zero tillage-flat bed with crop residue (ZT-F+R) and without crop residue (ZT-F), ZT-raised bed with crop residue (ZT-B+R) and without crop residue (ZT-B) and four sub plot treatments of nitrogen (N), i.e. 0, 60, 120 and 180 kg N ha−1. Most of the soil physical, chemical and biological parameters were significantly improved with ZT-B+R as compared to other treatments. ZT-B+R recorded 7.7 and 9.1% higher organic carbon than CT-B and CT-F, respectively. Microbial biomass carbon, dehydrogenase activity and fluorescein diacetate hydrolysis were improved by 57.4, 47.0 and 55.4% with ZT-B+R over CT-F, respectively. ZT-B+R also registered significantly lower bulk density compared to ZT without residue and CT-F treatments. The same treatment also improved the aggregation, hydraulic conductivity, infiltration rate and available N, P and K in soil. Root length density (RLD), root surface area (RSA) and root volume density (RVD) of maize and wheat were also recorded higher with ZT-B+R which was at par with CT-B and ZT-B, but significantly higher than CT-F and ZT-F treatments. Nitrogen levels did not exert significant influence on most of the soil properties, however, organic carbon and biological activities in soil improved up to 60 kg N ha−1, while soil available N, RLD, RSA and RVD improved significantly up to 120 kg N ha−1. Thus, we concluded that permanent-bed with crop residue (ZT-B+R) and 120 kg N ha−1 was found to be beneficial for improving soil health and root growth of maize and wheat crops.

Effect of conservation agriculture and nutrient management options on soil phosphorus fractions under maize-wheat cropping system

Effect of conservation agriculture and nutrient management options on soil phosphorus fractions under maize-wheat cropping system

Productivity, nutrient uptake and soil properties as influenced by integrated nutrient management in maize- wheat cropping system under rainfed conditions of sub- montane Punjab

In the present study, an attempt was made to assess the effect of integrated nutrient management in rainfed maize-wheat cropping system on productivity, nutrient uptake and soil properties. Field experiments were conducted for three years during 2014 to 2017 in a sandy loam soil at Regional Research Station, Punjab Agricultural University, Ballowal Saunkhri with nine treatments. Among different treatments, the treatment comprising 100% NPK through DAP + FYM @10 t ha−1 gave highest average grain yield (29.5 q ha−1 in maize and 26.1 q ha−1 in wheat), nitrogen uptake (31.3 kg ha−1 in maize grain and 24.8 kg ha−1 in wheat grain), phosphorus uptake (10.5 kg ha−1 in maize grain and 9.9 kg ha−1 in wheat grain) and potassium uptake (26.7 q ha−1 in maize grain and 22.3 q ha−1 in wheat grain), respectively. However, the net return (Rs 30,683 ha−1 year−1) and B:C ratio (1.55) was highest in the treatment 125%NPK followed by 100% NPK + ZnSO4 treatment (net return-Rs 29,966 ha−1 year1 and B:C ratio-1.55). In soil properties, the values of organic carbon (5.5 g kg−1), available phosphorus (37.2 kg ha−1), available potassium (205 kg ha−1) and microbial counts were highest in the treatment comprising of 100% NPK + FYM @10 t ha−1. Considering the positive effects on crop productivity and soil health, it can be concluded that integrated use of recommended 100%NPK through DAP with farmyard manure (10 t ha−1) is better nutrient management option under rainfed conditions of sub-montane Punjab.

Successive straw biochar amendments reduce nitrous oxide emissions but do not improve the net ecosystem economic benefit in an alkaline sandy loam under a wheat–maize cropping system

AbstractCrop straw is converted to biochar with subsequent applications to soils as a multi‐benefit strategy for greenhouse gas (GHG) emission mitigation, carbon sequestration, and straw disposal and utilization in intensive agriculture. However, tradeoffs between agronomic, economic, and environmental performance of long‐term agricultural biochar use remain unclear. Using a case study of biochar‐amended alkaline sandy loamy soil, we investigated the effects of field application of straw biochar at 0, 2.25, 6.75, and 11.25 Mg ha−1 to 10 successive wheat and maize crop seasons over five rotation years on crop yield, nitrous oxide (N2O) emissions, soil total organic carbon (TOC), and soil carbon pool (SCP). The net global warming potential (net GWP) and net ecosystem economic benefit (NEEB) were assessed to examine the tension between balancing economic returns and environmental benefits. Results indicated that biochar treatments slightly increased total crop grain yields and greatly reduced the total N2O emissions over five rotation years. The soil total organic carbon content was enhanced while the CO2 emissions during biochar production almost offset the increase in the soil carbon pool. Economic assessment showed that the net ecosystem economic benefit was lowered with enhanced costs of the increasing biochar use under the current low C trade market. These results highlight the promotion of the use of straw biochar in successive applications as a strategy to effectively offset greenhouse gas emissions from agriculture requires optimization of the straw pyrolysis system to reduce the energy consumption and overall biochar costs, and price enhancement of C trade.

Changes in soil organic carbon fractions and bacterial community composition under different tillage and organic fertiliser application in a maize−wheat rotation system

ABSTRACT The objective of this study was to assess the impact of different tillage and organic fertiliser regimes on soil carbon fractions and bacterial community composition within a maize–wheat cropping system. We conducted a six-year experiment on the Huang-Huai-Hai Plain of China. Six treatments were established: deep tillage (DT), shallow tillage (ST), no-tillage (NT), deep tillage with organic fertiliser (DTF), shallow tillage with organic fertiliser (STF), and no-tillage with organic fertiliser (NTF). Results indicated that during the winter wheat growing season, the highest contents of soil organic carbon (SOC) and easily-oxidised organic carbon (EOC) were in the STF treatment. During the summer maizegrowing season, the DTF treatment had the highest SOC and EOC contents. Compared with the other treatments, the NTF treatment had higher Chao1 and Shannon indices for bacteria; however, the relative abundance of Proteobacteria is highest in all treatments. A redundancy analysis (RDA) revealed that bacterial community composition was correlated with variation of the SOC, DOC, EOC, and microbial biomass carbon (MBC). Our results showed that combining the two components of the SOC fractions and bacterial community composition, STF practice in a maize–wheat rotation was a sustainable approach to optimising soil structure and improving soil quality.

Modeling the temporal distribution of water, ammonium-N, and nitrate-N in the root zone of wheat using HYDRUS-2D under conservation agriculture.

In the current study, the temporal distribution of both soil water and soil NO3-N under several conservation agriculture (CA) practices during the wheat crop growth were characterized by HYDRUS-2D model. Treatments comprised of conventional tillage (CT), permanent broad beds (PBB), zero tillage (ZT), PBB with residue (PBB+R) and ZT with residue (ZT+R). Hydraulic inputs of the model, comprising the measured value of Kfs, α and n, obtained as the output of Rosetta Lite model were optimized through inverse modeling. Model predicted the daily change in soil water content (SWC) of the profile during the simulated period (62-91 DAS) with good accuracy (R2 = 0.75; root mean squared error (RMSE) = 0.038). In general, soil water balance simulated from the model showed 50% lower cumulative drainage, 50% higher cumulative transpiration along with higher soil water retention, in PBB+R than CT. Reported values of the first-order rate constants, signify nitrification of urea to NH4-N (μa) (day-1) nitrification of NH4-N to NO3-N (μn) (day-1) and the distribution coefficient of urea (Kd-in cm3 mg-1) were optimized through inverse modeling. Later they were used as solute transport reaction input parameters of the model, to predict the daily change in NO3-N of the profile with better accuracy (R2 = 0.83; RMSE = 4.62). Since NH4-N disappears fast, it could not be measured frequently. Therefore, not enough data could be generated for their use in the calibration and validation of the model. Results of simulation of daily NO3-N concentration indicated a higher concentration of NO3-N in the surface layer and its leaching losses beyond the root zone were relatively lesser in PBB+R, than CT, which resulted in less contamination of the belowground water. Thus, the study clearly recommended PBB+R to be adopted for wheat cultivation in maize-wheat cropping system, as it enhances the water and nitrogen availability in the root zone and reduce their losses beyond the root zone.

Sustainable options for reducing carbon inputs and improving the eco-efficiency of smallholder wheat-maize cropping systems in the Huanghuaihai Farming Region of China

The large inputs to the winter wheat-summer maize cropping systems (WMSs) in the Huanghuaihai Farming Region (HFR) of China have increased resource consumption and pollution risk. The purposes of the current study were to seek effective ways to reduce the negative impacts of smallholder systems on the environment by using the life cycle assessment (LCA) method and data from field investigations and high-yield demonstration fields with WMSs in four representative counties across the HFR. High-yield demonstration fields with optimized fertilizer management had a higher carbon balance (CB), lower carbon intensity and higher fertilizer use efficiency than smallholder fields. The CB and carbon emissions differed among counties due to differences in input and output levels. Fertilizer application contributed the most to carbon emissions from WMSs in the HFR, accounting for 34.5% of the total carbon emissions. Thus, an efficient way to reduce the carbon footprint is to reduce the difference in nitrogen application between farmers’ and high-yield fields. The dominant WMS production unit in the HFR is smallholding, which requires large resource inputs and high carbon consumption for high yield. Therefore, optimizing the carbon input management of farmers’ fields, especially the management of fertilizers, is crucial for promoting high-yield, low-carbon production and improving ecological benefits for WMS smallholders in the HFR, which will further promote clean and sustainable agricultural production in this region.

Effect of long-term fertilization in maize-wheat cropping system on carbon mineralization in soil

Quantitative information on mineralization of soil organic carbon (SOC) under different long-term nutrient management practices is essential for better assessment of carbon (C) loss from soil. With an aim to evaluate long-term nutrient management effects on C mineralization kinetics in soils, a laboratory incubation study was conducted with soils collected from different depths (0–15, 15–30, 30–60, and 60–100 cm) of a 46-year old maize-wheat experiment. The treatments in the field involved long-term application of 100% N, 100% NP, 100% NPK, 150% NPK, 100% NPK + FYM (farmyard manure), and an unfertilized control. Long-term application of fertilizers significantly (p < 0.05) influenced organic C concentration and C mineralization kinetics in soil. Integrated application of inorganic fertilizers and organic manure (100% NPK + FYM) resulted in greater SOC accumulation and higher potentially mineralizable C in soil compared to other treatments. The microbial biomass carbon (MBC), basal soil respiration (BSR), carbon mineralization (Cmin), and microbial quotient (qMic) values were significantly higher under integrated application of NPK and FYM in maize-wheat system. The results showed that long-term application of FYM along with inorganic fertilizer enhanced SOC pool compared to solitary application of mineral fertilizers.

No-tillage did not increase organic carbon storage but stimulated N2O emissions in an intensively cultivated sandy loam soil: A negative climate effect

Although numerous studies have been conducted on the effects of no-tillage on carbon (C) sequestration in agricultural systems, there is still no consensus on the balance between the potential of C sequestration and nitrous oxide (N2O) or nitric oxide (NO) emissions. A no-tillage field experiment in the North China Plain was established in 2006 and the influence of no-tillage on N2O and NO emissions was monitored under an annual wheat-maize cropping system. The study included four treatments: no-tillage (NT) and conventional tillage (CT) soils amended with N fertilizer at a rate of 225 kg N ha–1 for wheat and 195 kg N ha–1 for maize (NTN and CTN) and without N fertilizer (NT0 and CT0). Three years of no-tillage significantly (p < 0.05) increased soil organic C (SOC) content by 12.2% in the 0–5 cm soil layer, possibly due to the surface aggregation of organic C derived from crop roots and exudates, but did not alter SOC pool in the 0–30 cm profile. Annual N2O emissions in the NT0 and CT0 treatments were 0.53 and 0.57 kg N2O-N ha–1, respectively, and were significantly (p < 0.05) increased to 0.96 kg N2O-N ha–1 in CTN and to 1.23 kg N2O-N ha–1 in NTN. Remarkable differences in N2O emissions between CTN and NTN were observed during the maize growing season. In contrast, NO emissions were not affected by the tillage regimes regardless of N fertilization. The mean ratios of NO/N2O fluxes in N-unfertilized plots were 0.26–0.29 and 1.79–2.11 for the maize and wheat season, respectively, indicating that both NO and N2O were primarily derived from denitrification during the maize growing season and from nitrification under wheat cultivation. Under N-fertilized plots, the ratios increased to 1.44–2.02 and 5.00–6.03 for the maize and wheat season, respectively, with significantly (p < 0.05) lower values in NTN plots than in CTN plots. The N2O emission factors for N applied in the wheat-maize rotation system were 0.16% and 0.09% for NTN and CTN, respectively, which was far lower than the IPCC Tier 1 default value (1.0%), primarily due to the absence of irrigation after fertilization in maize season and low temperature in wheat season. The results suggest that the 3-year no-tillage regime with residue removal did not substantially increase C storage in the 0–30 cm profile, but stimulated N2O emissions primarily by increasing denitrification.

Managing Tillage Operation and Manure to Restore Soil Carbon Stocks in Wheat–Maize Cropping System

Increasing soil organic matter (SOM) contents improve the resilience of productive soil for future sustainability particularly in poor soil (&lt;1% SOM). This study sought to elucidate how tillage and N fertilizer sources affect soil bulk density, soil organic carbon (SOC) and soil total N (TN) in 0‐ to 20‐cm soil depth. Treatments included minimum till (MT), conventional till (CT), deep till (DT), and twelve N treatments (60 and 120 kg urea N ha−1, 10 and 20 Mg farmyard manure [FYM] ha−1, 10 Mg soybean residue [SR] ha−1and their combinations along with a control). The experiment was designed in randomized complete block design with split plot arrangement. Soil bulk density increased for DT toward the end of the experiment than CT or MT. The sequestration rates of SOC of MT was 22% higher than DT. The FYM retuned more SOC than SR, however SR returned more TN than FYM. Application of FYM as well as SR sequestered more C than urea or control. Conclusively, SOC returned was increased with 10 Mg FYM ha−1along with 30 kg urea N ha−1but TN with 10 Mg SR ha−1in CT plots. This practice can therefore increase soil quality and productivity, and thus is considered a sustainable approach for soils deficient in organic matter.Core IdeasMinimum tillage improved C stock than shallow or deep tillage.The addition of urea increased SOC contents in SR plots than FYM.C Stocks in FYM and SR fertilized plots was about 3‐ to 4‐fold greater than control.Soybean residue build N stock principally in less plowed plots.

Simulation‐based Maize–Wheat Cropping System Optimization in the Midhills of Nepal

Rainfed maize (Zea mays L.)–wheat (Triticum aestivum L.) production in the midhill region of Nepal is limited in the winter season by cool temperatures, low rainfall, and low fertility. Here, we use the Decision Support System for Agricultural Transfer Cropping System Model (DSSAT‐CSM) to simulate potential productivity for conservation agriculture (CA) and conventional practice (CP), contrasting N application rates, and wheat planting dates ranging from 1 September to 15 December under six different weather scenarios in the midhills of Nepal. Total maize plus wheat aboveground biomass increased up to 56% with longer vs. shorter duration maize varieties, but the subsequent dry‐season wheat failed 71% of the time after late‐planted, long‐season maize in areas where mean seasonal temperature was below 14°C. The optimal wheat planting date increased from August to December as seasonal rainfall amount increased. Increasing N application rate in wheat from 50 to 150 kg ha–1 resulted in significant yield and net profit gains for all weather scenarios given current grain and fertilizer prices in the midhills, especially where conditions were cool and rainfall exceeded 400 mm. Principal component analysis of soil and climate parameters indicated that CA benefits most from higher N application rates when conditions are cool and wet due to increased residue retention coupled with slow soil organic matter decomposition.Core Ideas Conservation agriculture out‐yields conventional practice in wheat for weather scenarios with high seasonal rainfall. Insufficient growing degree days may force earlier than optimal wheat planting in cooler midhill weather scenarios. Optimal wheat planting date occurs before October in warmer and drier midhill weather conditions.

Effect of fertilizer application based on soil test crop response approach on active and passive pools of soil organic matter in maize–wheat cropping system

ABSTRACTA long-term fertilizer experiment was initiated in kharif 2007 in a maize–wheat sequence at the Experimental Farm of Department of Soil Science, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur under the network of All India Coordinated Research Project on Soil Test Crop Response (STCR) Correlation Studies. The experiment consisted of eight treatments (control, general recommended dose, soil test based, farmers’ practice, target yield of 25 (rabi)/30 (kharif) and 35 (rabi)/40 (kharif) q ha−1 either with or without 5 t ha−1 farm yard manure) replicated thrice in a randomized block design. All the passive and active pools of soil organic matter (SOM) were highest under STCR treatments for target yield 35 q ha−1 + farmyard manure (FYM). The highest value of both humic and fulvic acids under STCR treatment for target yield 35 q ha−1 with FYM was statistically at par with treatment for target yield 25 q ha−1 with FYM. The R2 value indicated that about 96% to 98% of the total variation in grain yield was attributable to SOM fractions. The contribution of all fractions of SOM towards the total variation in straw yield was 96% to 97%.

Diversification of maize-wheat cropping system with legumes and integrated nutrient management increases soil aggregation and carbon sequestration

Retention of carbon in arable soils has been recommended as an important mechanism to mitigate the climate change and sustainability of the agro-ecosystems. We reasoned that legume-inclusive crop rotations and integrated nutrient management would promote higher soil aggregation and carbon sequestration compared with continuous cereal-cereal [maize (Zea mays L.) – wheat (Triticum aestivum L.)] rotation and chemical fertilization. To test the hypothesis, we used a long-term field experiment (13 years) in Typic Ustochrept soil of Kanpur, India. The field experiment was undertaken in split-plot design comprised of four crop rotations: maize–wheat (MW), maize–wheat–mungbean (Vigna radiata L.) (MWMb), maize–wheat–maize–chickpea (Cicer arietinum L.) (MWMC) (2 years rotation), pigeonpea (Cajanus cajan L.)-wheat (PW) in main plot, and three nutrient management treatments: without fertilization (CT), recommended dose of inorganic fertilizers in the region (NPKSZnB), and integrated nutrient management (INM) in sub-plot. Water stable macroaggregates (>0.25 mm), aggregate ratio, mean weight diameter, and geometric mean diameter followed the order of PW > MWMb > MWMC > MW (p < 0.05) for crop rotations, and INM > NPKSZnB > CT (p < 0.05) for nutrient management practices. The PW rotation and INM practice retained higher coarse macroaggregated- and ‘silt + clay’-carbon compared with MW and NPKSZnB treatments. The PW and MWMb rotations allocated 69.7 and 65.7% carbon in macroaggregates, respectively. While, MW rotation allocated higher carbon in microaggregates (55%). The PW and MWMb rotations significantly enhanced the active (very labile + labile) and passive (less labile + non labile) carbon pools compared with that of MW rotation. The PW stabilized 15% higher carbon in less labile fraction (Cfrac3) over the MW (p < 0.05). It indicated that higher passive carbon pool and its stabilization in PW and MWMb rotations could promote the carbon sequestration. Therefore, MWMb and PW systems had 14.7 and 3.9% higher carbon management index than that of MW rotation (p < 0.05). Among nutrient management treatments, INM resulted in higher active (26%) and passive (8%) carbon pools compared with that of NPKSZnB. Further, INM increased carbon management index by 29 and 16% (p < 0.05) compared with those of CT and NPKSZnB, respectively. Principal component analysis indicated that PW(INM) and MWMb(INM) distinctly situated from MW(CT) and MW(NPKSZnB) in coordinates. Thus, PW and MWMb rotations with INM practice can enhance the soil aggregation and carbon sequestration in long-run. The research findings can be extrapolated in the South Asian and other countries, where continuous cereal-cereal induced soil health issues are a pervasive problem.