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.

To evaluate the effects of conservation agriculture (CA) on SOC pools and their lability, field experiments (2015–2020) were conducted on contrasting soils under subtropical climates. The experiment on non-calcareous soils, was comprised of tillage (minimum [MT] vs. conventional [CT]) in main plots, cropping systems (Wheat [Triticum aestivum]—Aus and Aman rice [Oryza sativaL.], WRR; Lentil [Lens culinaris]—Aus and Aman rice, LRR; and Mustard [Brassica nigra]- Boro and Aman rice, MRR) in the sub-plots, and crop residue (with or without 20% residue) in the sub-sub plots. The experiment on calcareous soils, was comprised of tillage (strip-till, ST; no-till, NT; and CT) and crop residue (high residue, HR at 50% by height vs. low residue, LR at 15%). Results showed that the MT had higher SOC contents by 18.8% than the CT in non-calcareous soils. Likewise, SOC was 12.5% and 6.7% higher in the NT and ST, respectively, than in the CT in calcareous soils. Significantly higher particulate organic (POC), permanganate oxidizable (POXC), and microbial biomass carbon (MBC) were observed in the MT, NT, and ST than in the CT at both locations. Reduced tillage with residue retention under LRR had a higher SOC, including labile C pools compared to WRR and MRR systems. Similarly, carbon management index (1.2–1.5 and 1.0–1.2) in both soils had significant positive correlations with SOC lability via POXC, POC, and MBC pools, indicating a SOC sequestration potential. In conclusion, our results showed positive effects of CA on SOC and its lability across soils.

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-based systems of the EIGP of Bangladesh.

Legumes in Conservation Agriculture (CA) have the potential to increase crop productivity and sustainability of the rice-based system. However, there is limited information available on the importance of legume crops in CA in the rice-based system of the Eastern Indo-Gangetic Plain (EIGP). Rice-based cropping is the mainstay of the people in Bangladesh, on the EIGP. These systems are the major food supplier to the region. In addition, they provide income and employment opportunities to the majority of people in the region. However, the system is facing unprecedented challenges and increased risk due to water, energy, labour and capital scarcity, which are exaggerated due to the effects of climate change. This could be further aggravated by deteriorating soil health, depleting underground water, and reduced land and water productivity which ultimately threaten sustainable food production and food security of the EIGP. Hence, sustainable crop intensification is essential, but increasing cropping intensity has reduced the yield of single crops by degrading soil properties. To address these constraints, Conservation Agriculture (CA), with a minimum tillage system, residue retention and crop diversification with legumes, could be an effective approach for improving crop productivity while sustaining the natural resources in intensive rice-based systems of EIGP. The addition of legumes in crop rotation is a suitable technique for crop diversification due to its multiple benefits related to soil health and natural resources. Diverse legume crops involving rice-based cropping have already existed at different agro-ecological zones in Bangladesh, and their rotation definitely could act a major role in promoting the CA in rice-based systems. Legumes-based rotation offers multiple benefits, such as biological nitrogen fixation, improves soil pores through the deep root system, P-availability, soil fertility and enhance nutrient cycling, and reducing the use of external input and thereby minimizing greenhouse gas emission and groundwater pollution, improving water productivity, and minimizes diseases and pests incidence. As a result, crop rotation with legumes has a high potential for CA and sustainable rice-based cropping systems in Bangladesh. The gaps between legume and non-legume crops in CA for each parameter suggest a noteworthy possibility for the improvement of rice-based systems in EIGP. This review suggests further sustainability improvements can be achieved through future field research focused on the inclusion of legume crops in the diverse rice-based systems under CA.