Conservation agriculture for rice-based intensive cropping by smallholders in the Eastern Gangetic Plain

We review the recent development of Conservation Agriculture (CA) for rice-based smallholder farms in the Eastern Gangetic Plain (EGP) and the underpinning research on agronomy, weed control, soil properties and greenhouse gas emissions being tested to accelerate its adoption in Bangladesh. The studies are based mostly on minimum soil disturbance planting in strip planting (SP) mode, using the Versatile Multi-crop Planter (VMP), powered by a two-wheel tractor (2WT). One-pass SP with the VMP decreased fuel costs for crop establishment by up to 85% and labour requirements by up to 50%. We developed strip-based non-puddled rice (Oryza sativa) transplanting (NPT) in minimally-disturbed soil and found that rice grain yield increased (by up to 12%) in longer-term practice of CA. On farms, 75% of NPT crops increased gross margin. For non-rice crops, relative yield increases ranged from 28% for lentil (Lens culinaris) to 6% for wheat (Triticum aestivum) on farms that adopted CA planting. Equivalent profit increases were from 47% for lentil to 560% for mustard (Brassica juncea). Moreover, VMP and CA adopting farms saved 34% of labour costs and lowered total cost by up to 10% for production of lentil, mustard, maize (Zea mays) and wheat. Effective weed control was obtained from the use of a range of pre-emergent and post-emergence herbicides and retention of increased crop residue. In summary, a substantial body of research has demonstrated the benefits of CA and mechanized planting for cost savings, yield increases in many cases, increased profit in most cases and substantial labour saving. Improvement in soil quality has been demonstrated in long-term experiments together with reduced greenhouse gas emissions

Carbon and nitrogen mineralization in dark grey calcareous floodplain soil is influenced by tillage practices and residue retention

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

Establishment of crops under minimal soil disturbance and crop residue retention in rice-based cropping system: Yield advantage, soil health improvement, and economic benefit

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 followed the sequence as ZT > ST > BP > CT practice. The higher amount of residue retention significantly increased SOM, TN and extractable P, K, S and Zn concentrations at 0–5 cm and 5–10 cm soil depths. The 3-year study suggests that ST with RH is a potential crop management approach for the seasonally flooded rice-lentil/wheat-jute cropping systems to enhance soil nutrients status, crop yield and farm economy

Rice (Oryza sativa L.) establishment techniques and their implications for soil properties, global warming potential mitigation and crop yields

Rice-based intensive cropping systems require high input levels making them less profitable and vulnerable to the reduced availability of labor and water in Asia. With continuous conventional puddled rice transplanting, the situation is exacerbated by damaged soil structure, declining underground water and decreasing land and water productivity. To minimize these negative effects a range of new crop establishment practices have been developed (zero tillage, dry direct seeding, wet direct seeding, water seeding, strip planting, bed planting, non-puddled transplanting of rice, mechanical transplanting of rice crop and combinations thereof) with varying effects on soil health, crop productivity, resource saving and global warming mitigation potential. Some of these allow Conservation Agriculture (CA) to be practiced in the rice-based mono-, double- and triple cropping systems. Innovations in machinery especially for smallholder farms have supported the adoption of the new establishment techniques. Non-puddling establishment of rice together with increased crop residue retention increased soil organic carbon by 79% and total N (TN) in soil by 62% relative to conventional puddling practice. Rice establishment methods (direct seeding of rice, system of rice intensification and non-puddled transplanting of rice) improve soil health by improving the physical (reduced bulk density, increased porosity, available water content), chemical (increased phosphorus, potassium and sulphur in their available forms) and biological properties (microbiome structure, microbial biomass C and N) of the soil. Even in the first year of its practice, the non-puddled transplanting method of rice establishment and CA practices for other crops increase the productivity of the rice-based cropping systems. Estimates suggest global warming potential (GWP) (the overall net effect) can be reduced by a quarter by replacing conventional puddling of rice by direct-seeded rice in the Indo-Gangetic Plains for the rice-based cropping system. Moreover, non-puddled transplanting of rice saves 35% of the net life cycle greenhouse gases (GHGs) compared with the conventional practice by a combination of decreasing greenhouse gases emissions from soil and increasing soil organic carbon (SOC). Though the system of rice intensification decreases net GHG emission, the practice releases 1.5 times greater N2O due to the increased soil aeration. There is no single rice establishment technology that is superior to others in all circumstances, rather a range of effective technologies that can be applied to different agro-climates, demography and farm typologies

Comparative adaptable agronomic traits of blackgram and mungbean for saline lands

Blackgram, variety BARI Mash-1 and mungbean variety BARI Mung-5 were tested under five salinity levels (0, 30, 60, 90 and 120 mM NaCl) in a shade house at Agronomy research field of Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur, Bangladesh during 2014 to investigate the comparative agronomic traits of black gram and mungbean as influenced by salt stress. In both crops, salinity stress remarkably reduced the morphological characteristics viz plant height, number of branches per plant and yield attributed traits such as total pods per plant, pod length, grains per pod, 100-grain weight as well as grain yield and stover yield per plant. Under all salinity levels, black gram produced the lower reduction of number of grains per pod than mungbean. Althrough, mungbean produced the higher 100-grain weight than in black gram in control treatment but the reduction was finally more in mungbean than black gram due to salt stresses. Black gram and mungbean showed 36.71% and 49.45% reduction of 100-grain weight, respectively under 90 mM NaCl salt stress. The grain yield per plant highly hampered in mungbean (97.62% to control) while black gram showed about 86.75% reduction under high salt stress (120 mM NaCl). Blackgram may be considered more salt tolerant than mungbean byenvising all of the above parameters

Modification of nutrient requirements for a four Crop-Based cropping system to increase system productivity, maintain soil fertility, and achieve sustainable intensification

Sustainable and resilient cropping intensity is now a global focus to address the food demand and nutrition security of the growing population. For sustainable intensification, maintaining soil fertility is a key concern. The nutrient management for the recently developed four crop-based cropping system in Bangladesh has not yet been studied. Hence, field experiments were conducted on the nutrient management of the four crop-based cropping system [Aus (pre-monsoon rice), Aman (monsoon rice), lentil, and mungbean] in calcareous soil in Bangladesh during the years of 2016/17 and 2017/18 to determine the appropriate fertilizer management package to improve crop productivity and sustain soil fertility. The experiment had six treatments assigned in a randomized complete block design with three replications. The treatments included T1 = control (without synthetic fertilizer), T2 = 50% recommended dose of fertilizer (RDF), T3 = 75% RDF, T4 = 100% RDF, T5 = 125% RDF, and T6 = farmers’ practice (FP). The results revealed that the 125% RDF significantly contributed to higher yields of all four crops. The rice equivalent yield (REY) was the highest for the fertilizer management of 125% RDF, which was 45.5%, 9.4%, and 12.2% higher than the control (T1), 100% RDF (T4), and FP, respectively. Considering the uptake of nutrients (N, P, K, S, Zn, and B) by the crops in the cropping system, the 125% RDF was superior to the other treatments. The nutrient management practices had a positive influence on the apparent nutrient recovery (ANR) efficiency of the cropping system. The fertilizer management of 125% RDF was also economically more profitable due to the increment in the cost–benefit ratio of 26.8%, 4.4%, and 4.9% over the control, 100% RDF, and FP, respectively. The results indicate that the current fertilizer recommendations and FP for aus, aman, lentil, and mungbean are not adequate for the change from the three crop to the four crop-based pattern, and an increased dose of fertilizer is required to increase the yield of each individual crop as well as the total system’s productivity. The fertilizer use efficiency is also higher for 125% RDF than the 100% RDF and FP indicating that to sustain the soil fertility in the four crop-based system, the current RDF and FP are not sufficient. This finding will help intensive cropping areas in preventing nutrient deficiencies that would lead to a reduction in the crop yield