Conservation agriculture based tillage and crop establishment options can maintain farmers’ yields and increase profits in South Asia's rice–maize systems: Evidence from Bangladesh

Rice–maize (R–M) systems are rapidly expanding in South Asia and Bangladesh due to higher yield and profit potential from rabi (winter) maize, its reduced water requirement compared to rice–rice systems, and increasing demand from poultry and fish feed industries. The current practice of growing puddled transplanted rice and maize with conventional, repeated tillage degrades soil structure, delays maize planting, and reduces its yield potential, increasing energy and labour requirements, ultimately leading to high production costs. Conservation agriculture (CA)-based tillage and crop establishment options such as strip or reduced tillage, and raised beds, may hold potential to increase yield, reduce crop establishment costs, and increase income of the farmers. The objective of this study was to evaluate the productivity and profitability of R–M systems under CA-based tillage and crop establishment options across a gradient of 69 farmers’ fields in Northwest Bangladesh. We evaluated four tillage and crop establishment options: reduced tillage; strip tillage; fresh beds; and permanent beds. Conventional-tilled (puddled) transplanted rice on flat followed by conventional-tilled maize on flat was included as a current practice. ANOVA for adjusted 4-year pooled mean revealed no significant treatment effects for yield and economic analysis parameters for rice (P≥0.05), but they were significant for maize and the R–M system (P≤0.05). Rice yields across tillage and establishment treatments over four years ranged from 4.6 to 4.9tha−1 while maize and R–M system yields ranged, respectively, from 7.8 and 12.5tha−1 under conventional tillage to 9.0 and 13.8tha−1 on permanent beds. Compared to conventional tillage, the average maize and system yield across fresh beds, reduced tillage, and strip tillage, was greater by 9.1% and 6.1%, respectively. Maize production costs ranged from US $922ha−1 with fresh beds to US $1,027ha−1 for conventional tillage. Maize net returns and benefit cost ratio (BCR), however, ranged, respectively, from $945ha−1 and 1.9 under conventional tillage to $1350ha−1 and 2.4 under permanent beds. We conclude that while CA-based tillage and establishment options may not have significant yield advantage over conventional tillage in rice, they have significant advantages in terms of reduced production cost and labour use, and increased net returns. For maize as well as for R–M system, while most options can provide yield benefits similar to conventional tillage, permanent beds exhibit a significant advantage (yield, net returns, etc.) over conventional tillage. Profitability was consistently greatest and significantly different (P≤0.001) under permanent raised beds compared to all other treatments. Considering our assessment of the profitability distributions and risk analysis, we conclude that both rice and maize planted sequentially on permanent beds and strip tillage can result in higher net income and BCR compared to conventional tillage practice.