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Studies of rice-based systems in the Indo-Gangetic Plain (IGP) have demonstrated the beneficial effects of Conservation Agriculture on soil organic carbon (SOC) status, along with increased soil health and crop productivity. However, it remains unclear as to the time for such treatments to have a positive effect. In this study of lentil-mung bean-rice and wheat-mung-rice rotations in Bangladesh positive effects of strip planting or bed planting, along with residue return, on SOC pools were apparent after 1.5 years, compared with intensive conventional tillage and limited residue return. Conventional tillage resulted in higher CO2 emission compared with strip planting or bed planting as did high residue return. In the cereal-dominated rotation, the strip planting system sequestered carbon at a rate of 0.24–0.53 Mg C ha−1 year−1 (at 0–0.15 m depth) while conventional tillage was associated with a carbon loss of 0.52–0.82 Mg C ha−1 year−1. In the legume-dominated rotation, neither practice sequestered SOC. Under strip planting, a minimum annual crop residue input of 1.7 Mg C ha−1 for the cereal-dominated system and 5.2 Mg C ha−1 for the legume-dominated system was required to maintain SOC at equilibrium. We conclude that strip planting with high levels of crop residue return can be an effective and quick strategy in either slowing the loss of SOC or improving C sequestration in the intensive rice-based systems of the Eastern IGP.

Conservation Agriculture (CA), which delivers multiple benefits for crop cultivation, is becoming increasingly popular worldwide. However, CA is not a single, ready-made or simple technology that can be adopted everywhere without necessary farm-level refinement. The CA practitioners may need to incorporate changes in practices and each needs a few years of experience to fully learn how to optimize the technology on a particular crop on each farm. Implementation of CA is challenging in resource-limited, intensively cropped and rice-based smallholder farms. This chapter is a reflection on lessons learned during the last two decades of research, farmers’ adoption and service providers’ (LSP) feedback on CA practice in rainfed and irrigated systems where farmers grow three crops per year including at least one transplanted rice crop. We review smallholder farmers and LSP affordable and preferred CA planters, and the performance of CA in crop establishment and management, weed management, role and involvement of farmers’ groups, farm level benefits, rice and upland crops. Case studies are also presented on the benefits of CA practice including resources optimization, long-term trends of crop yield and profit margin, soil organic carbon sequestration and greenhouse gas (GHG) implications. These lessons may be useful for new practitioners, extensionists, researchers, teachers, students and policy planners to implement CA in smallholder regions considering food security, soil health and livelihoods and their contribution to mitigation of global warming.

Sustaining productivity of the rice-based cropping systems in the Eastern Indo-Gangetic Plain (EIGP) requires practices to reverse declining soil fertility resulting from excessive tillage and crop residue removal, while decreasing production costs and increasing farm profits. We hypothesize that the adoption of conservation agriculture (CA), involving minimum tillage, crop residue retention and crop rotation, can address most of these challenges. Therefore, the effects of crop establishment methods – strip planting (SP), bed planting (BP) and conventional tillage (CT); and levels of crop residue retention – high residue (HR) and low residue (LR) on individual crop yield, system yield and profitability were evaluated in a split-plot design over three cropping seasons in two field experiments (Alipur and Digram sites) with contrasting crops and soil types in the EIGP. The SP and BP of non-rice crops were rotated with non-puddled rice establishment; CT of non-rice crops was rotated with puddled transplanted rice. In the legume-dominated system (rice-lentil-mung bean), lentil yields were similar in SP and CT, while lower in BP in crop season 1. A positive effect of high residue over low residue was apparent by crop season 2 and persisted in crop season 3. In crop season 3, the lentil yield increased by 18–23% in SP and BP compared to CT. In the cereal-dominated system (rice-wheat-mung bean), significant yield increases of wheat in SP and BP (7–10%) over CT, and of HR (1–3%) over LR, were detected by crop season 3 but not before. Rice yields under CA practices (non-puddled and HR) were comparable with CT (puddled and LR) in both systems. Improved yield of lentil and wheat with CA was correlated with higher soil water content. The net income of SP increased by 25–28% for dry season crops as compared to CT and was equal with CT for rice cropping systems. Conservation agriculture practices provide opportunities for enhancing crop yield and profitability in intensive rice-b

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-1for 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

Wetland rice cultivation contributes significantly to global warming potential (GWP), an effect which is largely attributed to emissions of methane (CH4). Emerging technologies for wetland rice production such as conservation agriculture (CA) may mitigate greenhouse gas (GHG) emissions, but the effects are not well defined. Investigations were carried out in an irrigated rice (Boro rice) field in the fifth crop after conversion of conventional tillage (CT) to strip tillage (ST). Two crop residue levels (low versus high, LR versus HR) and three nitrogen (N) application rates (N1 = 108, N2 = 144, and N3 = 180 kg N ha−1) were laid out in a split-plot experiment with three replicates. Yield-scaled GHG emissions and GWP were estimated to evaluate the impacts of CA on mitigating CH4 and N2O emissions in the rice paddy field. There was a 55% higher N2O emission in ST with HR coupled with N3 than that in CT with LR coupled with N1. The N2O emission factors ranged from 0.43 to 0.75% in ST and 0.45 to 0.59% in CT, irrespective of the residue level and N rate. By contrast, CH4 emissions were significantly lower in CA than in the conventional practices (CT plus LR). The ST with LR in N2 reduced the GWP by 39% over the GWP in CT with HR in N1 and 16% over the conventional practices. Based on our investigation of the combination of tillage, residue, and N rate treatments, the adoption of CA with high and low residue levels reduced the GWP by 10 and 16%, respectively, because of lower CH4 and N2O emissions than the current management practices. The relatively high N2O emission factors suggest that mitigation of this GHG in wetland rice systems needs greater attention.

Subtropical recent alluvial soils are low in organic carbon (C). Thus, increasing organic C is a major challenge to sustain soil fertility. Biochar amendment could be an option as biochar is a C-rich pyrolyzed material, which is slowly decomposed in soil. We investigated C mineralization (CO2-C evolution) in two types of soils (recent and old alluvial soils) amended with two feedstocks (sugarcane bagasse and rice husk) (1%, weight/weight), as well as their biochars and aged biochars under a controlled environment (25 ± 2 °C) over 85 d. For the recent alluvial soil (charland soil), the highest absolute cumulative CO2-C evolution was observed in the sugarcane bagasse treatment (1 140 mg CO2-C kg-1 soil) followed by the rice husk treatment (1 090 mg CO2-C kg-1 soil); the lowest amount (150 mg CO2-C kg-1 soil) was observed in the aged rice husk biochar treatment. Similarly, for the old alluvial soil (farmland soil), the highest absolute cumulative CO2-C evolution (1 290 mg CO2-C kg-1 soil) was observed in the sugarcane bagasse treatment and then in the rice husk treatment (1 270 mg CO2-C kg-1 soil); the lowest amount (200 mg CO2-C kg-1 soil) was in the aged rice husk biochar treatment. Aged sugarcane bagasse and rice husk biochar treatments reduced absolute cumulative CO2-C evolution by 10% and 36%, respectively, compared with unamended recent alluvial soil, and by 10% and 18%, respectively, compared with unamended old alluvial soil. Both absolute and normalized C mineralization were similar between the sugarcane bagasse and rice husk treatments, between the biochar treatments, and between the aged biochar treatments. In both soils, the feedstock treatments resulted in the highest cumulative CO2-C evolution, followed by the biochar treatments and then the aged biochar treatments. The absolute and normalized CO2-C evolution and the mineralization rate constant of the stable C pool (Ks) were lower in the recent alluvial soil compared with those in the old alluvial soil. T

Very little is known about the changes that occur in soil organic carbon (SOC) and total nitrogen (TN) under an intensive rice-based cropping system following the change to minimal tillage and increased crop residue retention in the Gangetic Plains of South Asia. The field experiment was conducted for 3 years at Rajbari, Bangladesh to examine the impact of tillage practices and crop residue retention on carbon (C) and nitrogen (N) cycling. The experiment comprised four tillage practices—conventional tillage (CT), zero tillage (ZT), strip-tillage (ST), and bed planting (BP) in combination with two residue retention levels—increased residue (R50%) and low residue (R20%—the current practice). The TN, SOC, and mineral N (NH4+-N and NO3−-N) were measured in the soil at different crop growth stages. After 3 years, ZT, ST, and BP sequestered 12, 11, and 6% more SOC, and 18, 13, and 10% more TN, respectively than the conventional crop establishment practice at 0–5 cm soil depth. The accumulation of SOC and TN was also higher compared to the initial SOC and TN in soil. Among the tillage practices, the maximum SOC and TN sequestration were recorded with ST and with R50% that might be attributed to reduced mineralization of C and N in soil particularly with increased residue retention, since decay rates of potentially mineralizable C was lower in the ST with both the residue retention practices. Increased residue retention and minimum tillage practices after nine consecutive crops has altered the C and N cycling by slowing the in-season turnover of C and N, reducing the level of nitrate-N available to plants in the growing season and increasing retained soil levels of SOC and TN.

Aim of the study: Firstly, to evaluate the K dynamics of soils through a quantity-intensity isotherm study; and secondly, to characterize the soils on the basis of quantity-intensity (Q/I) parameters. Area of study: Gazipur, Bangladesh Material and methods: Eleven soils collected from major agro-ecological zones in Bangladesh were evaluated for their varying K dynamics parameters, and K supplying capacities of these soils were described. Main results: The Q/I plot showed both linear and polynomial relationships for soils in the study. The eleven soils had labile K ranging from 0.022 in Palashbari clay loam to 1.35 cmol kg-1 in Barisal clay. The latter soil had the highest equilibrium K activity ratio (0.003 mol L-1)1/2 and potential buffering capacity (PBC) (460.4 (cmol kg-1) (mol L-1)1/2). The PBC of soils for non-exchangeable pool (PBCne) was much higher than that of exchangeable pool (PBCe) in most soils. The largest amount of PBCne and PBCe occurred in Barisal clay, Gopalpur clay, Jhalokathi clay and Nachol loam which had a higher K desorption rate than all the other soils. The equilibrium exchangeable K, critical exchangeable K and equilibrium solution K of the soils varied widely (0.0006-0.035, 0.06-0.61 and 0.06-0.604 cmol kg-1, respectively). The added K was converted almost equally for the respective soils, with specific reference to the respective exchangeable and non-exchangeable pool for Barisal clay and Nachol loam. Research highlights: All the studied parameters revealed wide variations among the soils. The linear and polynomial relationships for soils can efficiently characterize intensively cultivated soils in Bangladesh.

Minimum soil disturbance and increased crop residue retention practices are promising options to enhance soil organic matter, nutrient concentration and crop yield. However, the potentials of the practices in improving soil properties, increasing crop yield and in ensuring economic return have not been tested in the monsoon rice (Oryza sativa L.)-lentil (Lens culinaris L.)/wheat (Triticum aestivum L.)-jute (Corchorus culinaris L.) cropping systems on seasonally flooded lowlands of the Eastern Gangetic Plain of South Asia. A field trial for consecutive three years was conducted in the Gangetic Plains of Bangladesh to evaluate the effects of zero tillage (ZT), strip-tillage (ST), bed planting (BP) and conventional tillage (CT) with two residue retention levels (RL—a low level similar to current farmers’ practice and RH—increased retention) on soil properties, yield and economic return. Between rice and jute crops, lentil was grown for the 1st and 2nd years and wheat for the 3rd year during the dry winter season. The ST and BP performed better than the CT and ZT in terms of yield of rice and lentil, whereas ST and ZT performed better than other practices in the case of jute. Higher residue retention (RH) increased crop yield for all the years. The highest rice equivalent yield (sum of 3 crop yields, expressed as rice yield) and the greatest benefit-cost ratio (BCR) were recorded with ST and RH. The increased yield in the ST was associated with reduced soil bulk density (BD), while ST with RH increased soil water (SW) and decreased penetration resistance (PR) of soil. Compared to CT, minimum soil disturbance of ZT and ST increased soil organic matter (SOM) stock by 24% and 23%, respectively; total nitrogen (TN) by 23.5% and 18.4%, respectively; extractable sulphur (S) by 21% and 18%, respectively; whereas Zinc (Zn) concentrations increased by 53% and 47%, respectively, in the upper 0–5 cm soil depth. Accumulation of extractable P, S and Zn in the 0–5 cm depth of soil fo

Charland is newly developed land in river beds which is poor in fertility. Sugarcane bagasse (SB) biochar was produced and characterized, and its performances were evaluated on carbon sequestration and yields of maize and groundnut in charland. The bagasse after pyrolysis ≈ at 600°C temperature produced 55% biochar. The pH value increased from 6.5 (SB) to 8.8 (biochar), C from 42% to 58%, P from 0.11% to 0.23%, K from 0.83% to 1.32% and the S content from 0.12% to 0.61%; whereas the N content decreased from 2.03% to 1.17%. Seven treatments were implemented in field trials of 2016–17 and 2017–18 in Brahmaputra charland consisting of control, 100% chemical fertilizers (CF), CF+ Cowdung (10 t ha−1), CF+ biochar (5 t ha−1 broadcast), CF + biochar (10 t ha−1 broadcast), CF+ biochar (5 t ha−1 furrow application) and CF+ biochar (10 t ha−1 furrow application). Amendment was done in the year one. Results reveal that the same dose of cowdung or biochar with CF produced higher grain yields of maize and groundnut with 40–60% increase over sole CF treatment. Integrated use of 10 t ha−1 biochar with CF can ensure higher crop yield and sustained soil fertility in charland ecosystem.