Puddled and zero-till unpuddled transplanted rice are each best suited to different environments - An example from two diverse locations in the Eastern Gangetic Plains of Bangladesh

Rice is predominantly grown on puddled soils (puddling is achieved through wet tillage in ponded water to create a soft soil environment and impermeable sub-soil layer) in the Eastern Gangetic Plains (EGP) of Bangladesh. Puddling is often discouraged while practicing conservation agriculture (CA) to achieve maximum system benefit. Zero-till unpuddled transplanted rice (ZT UPTR) could be a good substitute for puddled transplanted rice (PTR) as it possesses all the benefits to fit in a CA-based system. However, the performance of ZT UPTR might vary in different soil types and environments. The nitrogen (N) fertilizer management might also vary for different rice establishment methods and irrigation management. Therefore, two replicated field experiments were conducted in two diverse sites in the EGP, with significant variation in soil type and agro-climatic conditions. Three rice establishment methods - PTR, ZT UPTR, and rainfed ZT UPTR (ZT RUPTR) were compared in the main plots and three N rates (0, 45, and 90 kg ha(-1), representing zero, half, and full recommended doses) were allocated in the sub-plots. We found that the recommended N management for both PTR and ZT UPTR was similar at both the sites, although the relative performance was different between the two different environments. In silt loam soil, the ZT UPTR performed equally or better than PTR (similar in the first season, a slight gain in grain yield in the second season). However, in sandy loam soil, the ZT UPTR performed slightly inferior to PTR (similar in the first season, lower grain yield in the second season). More water (about 564 mm) was required for growing ZT UPTR than PTR in the second season at the sandy loam site due to increased percolation rate in ZT UPTR caused by the cessation of puddling. Grain yield of ZT RUPTR was slightly lower (by 0.2 t ha(-1)) but statistically similar to PTR and ZT UPTR in both seasons in the silt loam soil, but significantly lower grain yield (by 1.5 t ha(-1)) in the first season and crop failure in the second season in the sandy loam soil. Therefore, ZT UPTR could be a feasible option in fine-textured soils for the establishment of rice in a CA-based system while its feasibility for coarse-textured soils seems limited and requires further study.

Automated summary

The study found that the performance of zero-till unpuddled transplanted rice (ZT UPTR) may vary in different soil types and environments in the Eastern Gangetic Plains of Bangladesh, requiring adjustments in nitrogen fertilizer management. In silt loam soil, ZT UPTR performed well, while in sandy loam soil, it performed slightly inferior to puddled transplanted rice (PTR).