Changes in soil organic matter, plant nutrients and system productivity under conservation agricultural practices in the rice-jute cropping system

Soil organic matter (SOM) is central to soil quality and nutrient cycling. In Bangladesh, depletion of soil fertility is a serious threat to sustainability of agricultural production due to high cropping intensity and agriculture practices based on conventional tillage and residue removal (Rijpma and Jahiruddin, 2004). In this situation, CA practices (minimum tillage, crop residue retention and diverse crop rotations) could be a good option for the improvement of soil quality and crop productivity in Bangladesh. However, CA practices are poorly developed for intensive rice-based cropping system and their effect on SOM, plant nutrients and system productivity have not yet been properly addressed. Hence, the present study was undertaken to monitor the changes in SOM and other plant nutrients with system productivity under CA practices in the rice-jute cropping system in the Low Ganges River Floodplain of Bangladesh

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

Banding of fertilizer improves phosphorus acquisition and yield of zero tillage maize by concentrating phosphorus in surface soil

Zero tillage increases stratification of immobile nutrients such as P. However, it is unclear whether near-surface stratification of soil P eases or hampers P uptake by maize (Zea mays L.) which needs an optimum P supply at/before six–leaf–stage to achieve potential grain yield. The aim of the three-year study was to determine whether P stratification, under zero tillage, impaired yield of maize and which P placement methods could improve P uptake on an Aeric Albaquept soil subgroup. Phosphorus fertilizer was placed by: (a) broadcasting before final tillage and sowing of seeds; (b) surface banding beside the row; and (c) deep banding beside the row (both the band placements were done at three–four leaf stage) Phosphorus treatments were repeated for 3 years along with three tillage practices viz.: (a) zero tillage (ZT); (b) conventional tillage (12 cm; CT); and (c) deep tillage (25 cm; DT). In the third year, all the tillage practices gave similar yield of Bangladesh Agricultural Research Institute (BARI) hybrid maize–5, but the highest grain yield was obtained by surface band P placement. After three years of tillage and P placements, the root mass density (RMD) at 0–6 cm depth increased significantly from 1.40 mg cm−3 in DT under deep band placement to 1.98 mg cm−3 in ZT under surface band placement, but not at the other depths. The combination of ZT practices, with broadcast or surface band placement methods, produced the highest available, and total P, content in soil at 0–6 cm depth after harvesting of maize. Accordingly, a significant increase in P uptake by maize was also found with surface banding of P alone and also in combination with ZT. Organic carbon, and total N, also increased significantly at depths of 0–6 cm after three years in ZT treatments with P placed in bands. By contrast, CT and DT practices, under all placement methods, resulted in an even distribution of P up to 24 cm depth. Phosphorus application, by surface banding at the three–four leaf stage, led to increased P uptake at early growth and silking stages, which resulted in highest yield regardless of tillage type through increased extractable P in the soil. Even though ZT increased P stratification near the soil surface, and it increased plant available water content (PAWC) and RMD in the 0–6 cm depth, as did surface banding, it did not improve maize grain yield. Further research is needed to understanding the contrasting maize grain yield responses to P stratification

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

Residue handling capacity of the versatile multi-crop planter for two-wheel tractors

Crop residue retention is one of the core principles of conservation agriculture (CA). However, the level of retention and residue handling characteristics depend on household use of residue, crop type, residue type (loose or anchored), freshness (or weathering status), water content in residue, soil type, soil water content in the field, type of implements used to sow the next crop, disease of previous crops, height of residue, etc. Over the last decade, innovations made to a wide range of 2-wheel tractor (2WT) seeding implements now permit reliable seeding into minimally disturbed soil and moderate levels of crop residue. This provides a window of opportunity to develop CA cropping systems for small holder farmers in Asia and Africa, not only in terms of reduced soil disturbance but also with respect to biomass cover and crop rotation. The Versatile Multi-crop Planter (VMP) was designed as multi-functional and multi-crop 2WT-based planter for smallholders with capability for seed and fertilizer application in variable row spacing (Haque et al., 2011) but its capacity for residue handling using single-pass shallow-tillage (SPST), strip tillage (ST), zero tillage (ZT), bed planting (BP), and conventional tillage (CT) has not been systematically tested

Impact of phosphorus placement methods after three years of different tillage practices on maize productivity and soil properties

Minimal soil disturbance under conservation agriculture may limit the supply of immobile nutrients (such as phosphorus) to plant roots due to stratification of these nutrients close to the soil surface. Maize (Zea mays L.) roots usually do not proliferate into the middle of the rows until the plant has six to seven fully emerged leaves but a high P concentration in maize prior to the 6-leaf stage will significantly increase final grain yield (Aldrich et al. 1986). Phosphorus availability is critical during the early stages of plant growth when the movement of P to plant roots (P absorption by the plant) is reduced with cold soil temperatures (Alley et al. 2009). This can occur during winter (rabi season) when most maize is grown in Bangladesh (Ali et al. 2009). Also P moves very little in soils, and thus, available soil P levels can be built with P fertilizer application appropriate for the tillage practice. The aim of present study was to determine the effects of tillage practices and P placement methods on soil physical, chemical and yield of maize crops on a Grey Terrace Soil in Bangladesh

Effects of minimum tillage practices and crop residue retention on soil properties and crop yields under a rice-based cropping system

Average cropping intensity is 191% in Bangladesh but cropping patterns are mainly rice-based (BBS, 2012). Depletion of soil organic matter as well as other plant nutrients is one of the most serious threats to the sustainability of agriculture in Bangladesh (Rijpma and Jahiruddin, 2004). Hence, conservation agriculture (CA) practices such as minimal soil disturbance, crop residue retention with suitable crop rotations could be a good option for Bangladesh. However, the effects of CA practices in intensive rice-based rotations on soil properties along with crop yields have not been adequately assessed in Bangladesh. The present study was undertaken to determine the effects of minimum tillage practices and crop residue retention on soil properties and crop yields under a rice-based cropping system

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