Conservation agriculture for increasing productivity, profitability and water productivity in rice-wheat system of the Eastern Gangetic Plain

There are increasing concerns about the negative effects of conventional tillage (CT), extreme climate events, increased weed incidence, and reduced availability of farm inputs on crop yield and yield stability, profitability, and water productivity in rice-wheat (R−W) systems of the Eastern Gangetic Plains (EGP) in South Asia. Conservation agriculture (CA)-based tillage practices have been proposed in the region to address these concerns. We analysed 84 on-farm trials’ data comparing CA-based practices with farmers’ CT practices in R−W systems of eastern Terai region of Nepal in the EGP. The objectives were to investigate crop and cropping systems productivity, profitability, yield stability, irrigation (WPi) and total water productivity (WP(r+i)), and fertilizer-use efficiencies of three CA- and one CT-based practices in R−W systems. Treatments included: (i) CT-based: puddled transplanted rice - conventional tillage wheat (PTR−CTW); (ii) CA-based: PTR − zero tillage wheat (PTR−ZTW); (iii) CA-based: direct-seeded rice − ZTW (DSR−ZTW); and (iv) CA-based: un-puddled transplanted rice − ZTW (UPTR−ZTW). Results showed that although there were no significant differences in yield of either rice or wheat or R−W system between CA-based and CT treatments, there was a significant reduction in production cost (by 245−369 USD ha−1) mainly due to reduced labor use and increased net gain (188−223 USD ha−1) in all CA-based R−W system. DSR−ZTW showed the highest yield stability and net profit, demonstrating its adaptability in the region. Among the irrigation applicators (35%) in rice, DSR used 107 mm (67 mm higher than PTR) irrigation water with WPi of 70% and 96% of PTR and UPTR, respectively due to the need of additional irrigation for crop establishment. In contrast, among the irrigation applicators (75%) in wheat, due to earlier sowing of ZTW, it required 18% less irrigation water resulting in 9% higher WPi compared to CTW. However, a follow-up study two years after completion of field trials revealed that no local farmers had continued CA-based practices mainly due to high weed pressure, lack of land leveling, inaccessibility of zero-till (ZT) drill machines, and lack of ZT service providers. Effective support systems incentivizing in land leveling, ZT machines, technical knowledge dissemination, and the development of integrated weed management practices for scaling-out strategies are essential to adopt CA-based practices. As the results have great implications to reduce production costs and increase farm profits, save energy and water, increase land and labor productivity, and improve food security of millions of smallholder farmers in the EGP, strong policy support to incentivize farmers to avoid the adoption barriers of CA-based practices is required.