Intensification and diversification increase land and water productivity and profitability of rice-based cropping systems on the High Ganges River Floodplain of Bangladesh

Abstract

In the High Ganges River Floodplain of Bangladesh, rice-based cropping systems with lower tillage, labor and irrigation water requirement and higher productivity and profitability are needed. To explore options for achieving this, a replicated cropping system experiment was conducted at Jessore to evaluate cropping system intensification with varying degrees of tillage and rice residue retention. Four cropping systems/establishment methods (CSE) were compared: CSE1: T.boro-T.aman (soil puddling and transplanting of both rice crops); CSE2: CTwheat-CTmungbean-T.aman (wheat and mungbean sown using a power tiller-operated seeder, PTOS, with full tillage (CT) and sowing in a single pass); CSE3: CTwheat-CTmungbean-CTDSaman (all crops sown using a PTOS with full tillage, dry seeded (DS) aman); CSE4: STwheat-STmungbean-STDSaman (all sown using a PTOS with strip tillage (ST)). Two levels of aman residue retention (removed; partial retention) were compared in sub-plots. Water was ponded on the T.boro fields from transplanting until shortly before harvest, while all aman crops were grown using safe alternate wetting and drying (AWD) water management.System productivity (rice equivalent yield, REY) of all wheat-mungbean-aman systems was significantly higher than that of the T.boro-T.aman system in the first and fourth years and when averaged over the four years (by 10% or 1.3tha−1). This was due to higher prices paid to farmers for mungbean and wheat, which more than offset their lower grain yields in comparison with T.boro yield. Irrigation input was lower, by 62–83%, in the wheat-mungbean-aman systems than the T.boro-T.aman system. The wheat-mungbean-aman systems were also economically superior to the T.boro-T.aman system in terms of higher gross margin (by 26%), net return (double) and benefit cost ratio (1.1 vs 1.0) due to both higher returns and lower cost of production. The total labor requirement of all systems was similar; however, it was more evenly distributed throughout the year in the triple cropping systems. Productivity of the wheat-mungbean-aman systems with T.aman and DSaman was similar, despite significantly higher yield of wheat (by 10% or 0.4tha−1) following DSaman, as this was countered by a consistent trend (non-significant) for lower yield of the DSaman than T.aman. However, gross margin of the systems with DSaman was 5% higher than with T.aman due to lower cost of production of the former. Changing from puddling and transplanting to dry seeding of aman reduced total irrigation input to the triple cropping system by 238–879mm (32–65%) over the four years. Establishment of wheat in 40cm of standing aman residues using the PTOS was excellent with both full and strip tillage. Partial aman residue retention gave significantly higher (by 0.8–0.9tha−1) system yield than residue removal from the second year onwards, due to consistent trends for higher yields of all crops (significant in the case of wheat and mungbean). There were no significant differences between the use of CT and ST in the wheat-mungbean-aman system for any of the measured parameters.The results suggest that intensification from T.boro-T.aman to a wheat-mungbean-aman system can increase system productivity and profitability and reduce irrigation requirement, and that replacement of T.aman with DSaman in the triple cropping system can be done with reduced irrigation input, increased wheat yield, and little effect on rice yield. Furthermore, tillage for all three crops can be reduced to strip tillage with no adverse effects on productivity or profitability. Long term studies are needed to determine the full impacts of the changes in crop intensification, establishment method, tillage and residue management on soil properties, irrigation requirement and crop performance.