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Biochar incorporation as a soil amendment has been shown to improve soil quality by sequestering carbon in soil for longer period of time. The two years field experiment was done at Agronomy research fields of Lovely Professional University, Phagwara, Punjab, India during 2018-19 and 2019-20 to probe the impact of biochar combined with organic and inorganic amendments on soil carbon pools of rice-wheat cropping system. The experiment was comprised with nine treatments viz., 100% Recommended Dose of Fertilizer (RDF), 50% RDF + Biochar, 50% RDF +25% FYM + Biochar, 50% RDF + 50% FYM + Biochar, 50% RDF +25% VC + Biochar, 50% RDF + 50% VC + Biochar, 50% RDF + 25% PM + Biochar, 50% RDF + 50% PM + Biochar, control (no fertilizer) and imposed in RBD design with three replications for each treatment. Pusa basmati 1121 and PBW550 varieties of rice and wheat was taken as a test crops. The results revealed that application of 50 % RDF + 50% PM + Biochar in rice and 50% RDF + 50% FYM + Biochar in wheat crop to soil significantly improved the soil carbon fractions i.e., Permanganate oxidizable carbon, Particulate organic carbon and Microbial biomass carbon at harvest of the crops during both years. This study has demonstrated that C pools in the soil can be enhanced by the biochar through stimulating soil microorganisms. Carbon storage in the soil is improved after biochar addition. By adding biochar with fertilizer and manures C sequestration can be enhanced. Based on the findings in this study, conventional fertilizer and manure application to soils could be associated with biochar through which multi-benefits (e.g., soil amendment, environment protection, and C sequestration) could be obtained simultaneously. Thus, converting rice straw to biochar for its application as soil amendment and C sequester decrease straw burning in open field in Northern India. [ABSTRACT FROM AUTHOR]

The performance of DNDC (DeNitrification-DeComposition) and RothC (Rothamsted Carbon model) in simulating soil organic carbon (SOC) storage in soils under rice (Oryza sativa L.) – wheat (Triticum aestivum L.), maize (Zea mays L.) – wheat and cotton (Gossypium hirsutum L.) – wheat cropping systems was evaluated on field and regional scale. Field experiments consisted of N, NP, NK, PK, NPK, FYM, N + FYM, NPK + FYM, and control (UF) treatments. DNDC and RothC over-estimated SOC storage by 0.35–1.16 Mg C ha−1 (6–21%) in surface layer with manure application, compared with inorganic fertilizer treatments by 1.01–1.16 Mg C ha−1 (14–18%). Although RothC only slightly over-estimated SOC stocks, DNDC provided a better match for measured versus simulated SOC stocks (R2 = 0.783*, DNDC; 0.669*, RothC, p <.05). Model validation on independent datasets from long-term studies on rice–wheat (R2 = 0.935**, DNDC; R2 = 0.920**, RothC, p <.01) and maize–wheat (R2 = 0.895** for DNDC and R2 = 0.967** for RothC, p <.01) systems showed excellent agreement between measured and simulated SOC stocks. On a regional scale, change in SOC storage under Scenario 1 (NPK) was significant up to 8 years of simulation, with no change thereafter. In Scenario 2 (NPK + FYM), DNDC simulated SOC storage after 10 years was 2.0, 0.4, and 1.4 Mg C ha−1 in three systems, respectively. Amount of C sequestered in silt + clay fraction varied between 0.31 and 0.97 kg C 10 years−1 (Mg silt + clay)−1 under Scenario 1, and between 0.78 and 2.67 kg C 10 years−1 (Mg silt + clay)−1 under Scenario 2. [ABSTRACT FROM AUTHOR]

Decline in soil organic carbon (SOC) due to intensive tillage and removal or burning of crop residues is considered a major threat to maintaining soil quality and meeting future challenges of food production at national and global scales. Adoption of conservation-agriculture practices (no till and residue retention) is necessary to promote soil structural stability and increases in SOC content and enzyme activities. We evaluated the impact of tillage and residue-management practices on yield, soil labile-C pools, aggregate stability and soil enzyme activities after seven cycles of a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system on the Indo-Gangetic Plain of India. Treatments included four combinations of tillage and crop establishment in rice (main plots), and three combinations of tillage and residue management in wheat (subplots). Irrespective of rice-establishment method, mean grain yield of no-till wheat with rice-residue mulch (NTW+RR) was 9% and 22% higher, respectively, than of conventional-till (CTW) or no-till wheat with no rice-residue mulch. Soil C pools (very labile, labile, less-labile and non-labile) were significantly higher under a no-till dry-seeded rice (NTDSR)–NTW+RR cycle than conventional-till puddled transplanted rice–CTW. Macro-aggregates (>0.25 mm) had higher labile C pools, glomalin content and enzyme activities than micro-aggregates. NTW+RR significantly increased soil C pools within both macro- and micro-aggregates. Compared with CTW, NTW+RR increased soil dehydrogenase, cellulase and alkaline phosphatase activities by 23%, 34% and 14%, and water-soluble organic C by 31%, and increased water-stable aggregates and mean-weight-diameter. NTDSR–NTW+RR increased SOC, enzyme activity, aggregate stability and wheat grain yield. Results indicated that soil labile-C pools across aggregate fractions were the most sensitive indicators of soil quality when determining the effects of changes in management practices. Furthermore, adoption of no till and residue retention may improve sustainability in rice–wheat systems of the Indo-Gangetic Plain. This 7-year study examined soil carbon pools, aggregate stability, enzyme activities and wheat yield under conservation and conventional tillage and residue-management practices in a rice–wheat system on the Indo-Gangetic Plain. Macro-aggregates (>0.25 mm) had higher labile C pools, glomalin content and enzyme activities than micro-aggregates. The combination of no-till direct-seeded rice with no-till wheat + rice residue increased SOC, soil enzyme activities, aggregate stability and wheat grain yield, indicating that adoption of no till and residue retention may improve sustainability in these rice–wheat systems. [ABSTRACT FROM AUTHOR]

Carbon (C) mineralization of crop residues is an important process occurring in soil which is helpful in predicting CO2 emission to the atmosphere and nutrient availability to plants. A laboratory experiment was conducted in which C mineralization of residues of rice (Oryza sativa), wheat (Triticum aestivum), maize (Zea mays), mungbean (Vigna radiata) and their mixtures was applied to the soil surface or incorporated into an Alfisols from Northwest India. C mineralization was significantly affected by residue placement and type and their interactions. Rice residue had a higher decomposition rate (k = 0.121 and 0.076 day−1) than wheat (0.073 and 0.042 day−1) and maize residues (0.041 day−1) irrespective of placements. Higher decomposition rates of rice and wheat were observed when placed on soil surface than incorporated in the soils. Additive effects of the contribution of each residue type to C mineralization of the residue mixture were observed. When mungbean residue was added to the rice/wheat or maize/wheat mixture, decomposition of the residue mixture was enhanced. Crop residues with low N and high C/N ratio such as maize, wheat, rice and their mixtures can be applied on the soil surface for faster C and N mineralization, thereby helping to manage high volumes of residues under conservation agriculture-based practices in northwest India. [ABSTRACT FROM AUTHOR]

The status of available macronutrients [phosphorus (P) and potassium (K)] and soil organic carbon (SOC) of the surface soil under a rice–wheat cropping system was studied in 40 districts of the Indo-Gangetic Plains (IGP) of India. The soil samples were collected from the farmers' fields in four transects (Trans-, Upper, Middle, and Lower Gangetic Plains) of the IGP. The selection of farmers, villages, blocks, and districts within an agro-climatic zone (ACZ) was done on the basis of a multistage statistical approach. The available macronutrients were characterized as low, medium, and high. In Trans-Gangetic Plains, SOC, available P, and available K were in the ranges of 0.06–0.86%, 6.7–85.1 kg ha−1, and 50–347 kg ha−1, respectively. In Upper Gangetic Plains, the respective values were in the ranges of 0.05–2.55%, 4.5–155.0 kg ha−1, and 45 to 560 kg ha−1. Similarly, in Middle Gangetic Plains, these values were in the ranges of 0.04–2.01%, 4.7–183.7 kg ha−1, and 72–554 kg ha−1, respectively. In Lower Gangetic Plains, respective values were 0.12–1.78%, 2.2–112.0 kg ha−1, and 83–553 kg ha−1. In Trans-Gangetic plains, the majority of the soils in the midplains ACZ representing intensively cultivated rice–wheat system area were low to medium in SOC and available P, whereas available K status was medium to high. Irrespective of the agroclimatic variations, more than 90% of the soils were low to medium in SOC and available P with a marginal deficiency of K. The majority of the coarse-textured soils in Shiwaliks were found to have low to medium SOC and available P, whereas less intensively cultivated arid zone soils were high in SOC, available P, and available K. In Upper and Middle Gangetic Plains, the majority of the soils tested medium for SOC and medium to high in available P and K. The dominance of medium status of available P in these soils could be due to mining of soil P by the rice–wheat cropping system practiced in these regions for more than 300 years. In Lower Gangetic Plains, the SOC was medium to high in most of the soils, whereas available P and K were high. Recent introduction of the rice–wheat system on intensive scale in these traditionally rice-growing areas resulted in less mining of SOC, P, and K. [ABSTRACT FROM PUBLISHER]

We describe a summary model for the dynamics of carbon and nitrogen under varying weather, crop and soil conditions to investigate the role of soil organic carbon and nitrogen in yield formation in rice-based cropping systems of the Indo-Gangetic Plains (IGP). The model consists of three modules: soil organic matter (SOM), soil (SOIL), and crop growth (CROP). The SOM module consists of three pools: fresh, labile and stable. Carbon and nitrogen dynamics in the model are described in terms of carbon turnover, assimilation and dissimilation, with nitrogen linked through distinct C/N ratios. The SOIL module has two soil layers of variable depth (often 15cm each), and the labile and stable pools are replicated for these two layers. Water, crop and soil management practices and aeration characteristics of these layers affect the C and N dynamics of their respective pools. The CROP module calculates potential and actual biomass, leaf area index (LAI), evapotranspiration, total N demand, actual N uptake and N stress. Actual biomass is first partitioned between above (leaves, stem and storage organs) and below ground (roots and rhizodeposition), and a harvest index (HI) is applied to the aboveground biomass to calculate the yield. Independent data sets of 9 long-term experiments (LTEs) from the IGP of India were used for calibration and validation of the model. After calibration and validation, the model was used to explore the impact of various crop and soil management practices in rice-based cropping systems on different sites of the IGP. Overall, the model satisfactorily reproduced observed crop yields, SOC dynamics and total soil N dynamics for various cropping systems at different sites. Nitrogen mineralized from soil organic nitrogen contributed 5–75% to total N uptake in fertilized and non-fertilized treatments. With a recommended NPK application, a trend of significant decrease in simulated rice yield was found only at Ludhiana-3, and Pantnagar. Similarly, the simulated wheat yield also showed a significant trend of decline at Ludhina-3, Pantnagar and Barrackpore. Simulated SOC had a significant decline at Pantnagar, whereas at Ludhiana-3, it showed a significant increase. An increase in SOM is not always associated with an increase in yield, as the factor(s) improved by an increase in SOM may not be the limiting factor for crop growth. Depletion of many major macro (NPK) and micro (Zn, Fe, Mn, etc.) nutrients, essential for plant growth even with a balanced NPK fertilizer application and a maintained SOC, can lead to a decline in productivity. [Copyright &y& Elsevier]

Abstract: Soil organic carbon sequestration rates over 20 years based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to determine the potential for soil C sequestration in wheat-based production systems on the Indo-Gangetic Plain (IGP). The C sequestration potential of rice–wheat systems of India on conversion to no-tillage is estimated to be 44.1MtC over 20 years. Implementing no-tillage practices in maize–wheat and cotton–wheat production systems would yield an additional 6.6MtC. This offset is equivalent to 9.6% of India''s annual greenhouse gas emissions (519MtC) from all sectors (excluding land use change and forestry), or less than one percent per annum. The economic analysis was summarized as carbon supply curves expressing the total additional C accumulated over 20 year for a price per tonne of carbon sequestered ranging from zero to USD 200. At a carbon price of USD 25MgC−1, 3MtC (7% of the soil C sequestration potential) could be sequestered over 20 years through the implementation of no-till cropping practices in rice–wheat systems of the Indian States of the IGP, increasing to 7.3MtC (17% of the soil C sequestration potential) at USD 50MgC−1. Maximum levels of sequestration could be attained with carbon prices approaching USD 200MgC−1 for the States of Bihar and Punjab. At this carbon price, a total of 34.7MtC (79% of the estimated C sequestration potential) could be sequestered over 20 years across the rice–wheat region of India, with Uttar Pradesh contributing 13.9MtC. [Copyright &y& Elsevier]

Different integrated crop management (ICM) modules have been developed to enhance the productivity and profitability of the rice-wheat rotation (RWR) of the upper Indo-Gangetic Plains (IGPs). As the available options are used quite often singly or with the few combinations, hence in the present study, eight ICM modules have been evaluated; wherein, ICM 1&2 - conventional transplanted rice fb flatbed wheat, ICM 3&4 - conventional direct seeded rice (DSR) fb furrow irrigated raised bed wheat without residues, ICM 5&6 - conservation agriculture (CA)-based modules [zero tilled (ZT) DSR and ZT wheat] with the wheat and rice residues, and ICM 7&8- CA-based modules (ZTDSR and ZT wheat) with the wheat, mungbean and rice residues. Results revealed that ICM 8 produced the highest mean rice grain yield, which was statistically similar to ICM 1&7 , however it was 10.1–20.7% greater than the ICM 2–6 modules. Similarly, the ICM 7 recorded 14–16% greater wheat grain yield than the ICM 1–6 (five years' mean), but it was at par to the ICM 8. Furthermore, the ICM 7&8 produced 10–13% (5 years av.) higher system yields in terms of rice equivalents over the ICM 1&2. Water use (WU) was the highest in ICM 1&2 and was 8–12% higher than the ICM 3–8. In contrast, the highest water productivity (WP) was recorded with the ICM 7&8 , wherein it was14–16% greater than the ICM 1&2. The ICM 1&2 had incurred the highest variable production costs (US$ 912–1105 ha−1 yr−1), followed by ICM 7&8 (US$ 856–1021 ha−1 yr−1). Nevertheless, on an average, the ICM 7&8 gave 19–22% additional returns than the ICM 1&2. Also, the ICM modules had a significant (p < 0.05) and positive impact on the soil carbon (0.0–0.45 m). The CA-based (ICM 5–8) residue retained modules registered a 10–25% greater total OC stock than the ICM 1–4 in 0.0–0.45 m soil layer. The current study thus up-holds the importance of adequate inputs integration, and hence, adoption of the CA-based ICM in the RWR improved the soil carbon dynamics, crop yields, farm profits, besides water savings of the upper Indo-Gangetic Plains (IGPs) of north-west India. • ZTDSR-ZT wheat (ICM 7&8) had a positive impact on the system yields (10–13%) and farm economics (19–22%) than CT modules (ICM 1&2). • Residue retained ZTDSR-ZT wheat (ICM 5–8) contributed 12–17% greater total OC stock than the CT practices (ICM 1–4). • Modules ICM 5–8 saved 8–12% water and increased the system water productivity by14-16% than the CT rice and wheat (ICM 1&2). • Synergistic effects of ICM components reflected in complimenting the supply of nutrients besides conserving soil fertility. [ABSTRACT FROM AUTHOR]