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.

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.

Smallholders in Asia and Africa require low-cost seed drills for minimal soil disturbance while establishing various crops. A seed drill that can be drawn by the widely-available two-wheel tractor (2WT) is an attractive option for mechanization of no-till in small-sized fields. The Versatile Strip Seed Drill (VSSD) was designed with the capacity to make up to 40 mm wide and 60 mm deep strips in untilled land along with seed and basal fertilizer application in a single-pass operation, while powered by the 8.95 to 11.93 kW 2WT. An important innovation of the VSSD was to fit the seed box with both fluted roller-type seed meters for delivery of sufficient small-size seeds to achieve adequate plant density per unit row length; and vertical disk-type seed meters for precision and spaced row planting of larger seeds. Both incessant seed dropping by fluted roller seed meters and spaced planting by vertical disk type seed meters provided optimum plant populations that were generally higher than in conventional, full-tillage plots with the same rate of hand broadcasted seed and fertilizers. Time required for crop establishment by VSSD ranged from 0.13 to 0.18 ha·h⁻¹. When the VSSD was attached to the 2WT for crop establishment, the diesel fuel consumption varied from 4.4 to 6.1 L·ha⁻¹, which was lower than for most 2WT-based planters previously used in Bangladesh. In on-farm multi-locations trials, wheat crops established with the VSSD had statistically similar grain yield compared to conventional tillage; however, significantly higher grain yield was obtained from mustard and lentil, by 14% and 19%, respectively. The VSSD is a unique, minimum-soil-disturbance multi-crop planter, and can be a platform on which to build conservation agriculture systems for small farms in Asia and Africa.

Transplanting rice (Oryza sativa L.) seedlings into non-puddled soils with minimum soil disturbance (by mechanized strip tillage) is an opportunity to expand Conservation Agriculture (CA) adoption in rice-based cropping systems. However, the farmer acceptance and on-farm profitability of this technology has not been assessed. Here, we analysed farmer-managed non-puddled transplanting (NT) of rice seedlings in paired comparisons with rice seedlings transplanted in puddled (PT) soil. Sixty-six rainfed monsoon (aman) and 84 dry-season irrigated (boro) rice crops were established by NT and compared with paired PT crops during 2013–2015 in north and north-west Bangladesh. Non-puddled fields were prepared by firstly making 40–60-mm-wide tilled strips with a Versatile Multi-crop Planter, then by 18–24-h inundation with water to soften soils in the strip, followed by transplanting seedlings into strips. The NT crops produced similar or significantly greater grain (boro season of 2015) and straw yields than paired PT crops. The minimum soil disturbance NT did not hinder seedling transplanting of rice or increase the total labour costs for transplanting and weeding compared to PT, rather it reduced the cost of production, and increased net benefit for rice in both seasons relative to PT. Under farmer management on a range of soils and in the two main rice-growing seasons, NT performed as well or better than PT suggesting that this is a feasible option for farmers planning to adopt CA in rice-based cropping systems. Over 3 years, farmers’ perception of NT performance shifted from scepticism to mostly favourable.

When farmers first shift from conventional tillage (CT) to conservation agriculture (CA) practices, the control of weeds may be more difficult, due to the absence of tillage. However, continuous CA, over several years, may alter the weed seedbank. The nature of the weed seedbank changes over time, in intensively cropped rice-based rotations that are typical of the Eastern Gangetic Plain, are not well understood. Two on-farm CA experiments were sampled (in Beluapara after 3 years and Digram after 5 years) in Bangladesh for the effects of strip planting (SP) and bed planting (BP) at both the sites, plus no-tillage (NT) in Beluapara, and increased retention of the residue of previous crops (20% vs. 50%). The conventional tillage (CT) and 20% residue was the control treatment. The weed seedbank in 0–15 cm soil was quantified by assessing the emergence of weeds from soils collected from the field after irrigation, (Boro) rice in Digram and wheat in Beluapara, and they were allowed to emerge in trays in a shade-house experiment. The year-round count of emerged weeds at both the locations revealed the fewest number of weed species (especially broadleaf weeds), and the lowest weed density and biomass in SP, followed by CT, BP, and NT, with 50% crop residue mulch. Relative to CT, the SP, BP, and NT produced relatively more perennials weeds, as follows: Alternanthera denticulata ((R.) Brown.), Cyperus rotundus (L.), Dentella repens (L.), Jussia deccurence (Walt.), Leersia hexandra (L.), and Solanum torvum (Sw.), which was the opposite of CT that was enriched with the following annual weeds: Cyperus iria (L.), Digitaria sanguinalis (L.), Euphorbia parviflora (L.), Fimbristylis miliacea (L.), Lindernia antipoda (L.), L. hyssopifolia (L.), and Monochoria hastata (L.). The soil weed seed bank reduced by 13% in SP, while it increased by 19% and 76% in BP and NT, respectively, compared with CT. The species diversity reduced in SP and NT, by 24% and 11%, respectively, but increased by 2% in BP. In 50% residue, the soil weed seed bank and species diversity reduced by 16% and 14%, respectively, relative to that of 20% residue. The continuous practice of CA, for 3 or more years, in two rice-based crop rotations, decreased the size of the weed seedbank, but increased the relative proliferation of specific perennial weeds.

The extent to which Conservation Agriculture (CA) practices alter nitrogen (N) balance in intensive rice-based cropping systems of the Eastern Indo-Gangetic Plain was examined, focusing on a legume dominated-system (LDS) and a cereal dominated-system (CDS) in north-west Bangladesh. Three crop establishment methods were imposed—strip planting (SP) and bed planting (BP) for non rice crops with non-puddled rice establishment; compared with conventional tillage (CT) for non rice crops along with puddled transplanting of rice. Two levels of crop residue retention were superimposed—high (HR) and low (LR - conventional farm practice) crop residue retention. The CA practices (SP and non-puddled rice with HR) increased total soil N concentrations, and the soil N-stocks at 0–0.075 m over CT and LR in both CDS and LDS sites after 2.5 years. At 0–0.15 m soil depth, total soil N concentrations increased over time under SP and BP, but decreased with CT. In LDS, annual soil N increase (65 kg N ha⁻¹) occurred with SP while negligible N losses were observed under CT at both levels of residue retention at 0–0.15 m soil depth. The N accumulation rate under HR was 24.5 kg N ha⁻¹ higher than LR. The N balance calculation over 2.5 years indicated an estimated soil N gain (8–11%) in SPHR and SPLR but a loss in CT. In CDS, neither treatments accumulated soil N but N losses were greater in CT. The effect of crop establishment methods on soil NH₄-N and NO₃-N at the early growth stage of cool dry season cropping was small and inconsistent. However, SP with HR maintained higher overall crop and system N uptake compared to CT and LR. Thus, CA practices altered the N balance which slowed the decline in soil N-stocks in the cereal-dominated rotation while resulting in a positive N balance in the legume-dominated rotation.