Transplanting date adjustment in Boro rice cultivation as a strategy to reduce groundwater withdrawal in Bangladesh

Due to intensive irrigated rice cultivation during dry season, declining trend of groundwater level is observed in many parts of Bangladesh. Field experiments were conducted in 2015 and 2016 at four experimental stations of Bangladesh Institute of Nuclear Agriculture, Bangladesh to evaluate the performance of some Boro rice cultivars in different planting dates with respect to yield and irrigation water requirement, and to optimize between yield and irrigation water requirement, with a view to reduce groundwater withdrawal and hence reducing mining of groundwater. The transplanting dates were 21th January (T1), 15th February (T2), 7th March and 30th March. Four rice cultivars were used. The results showed that the rice growth period was shortened with the later dates of transplanting. Generally, the yield of all cultivars at first and second transplanting (i.e. in T1 & T2) are good, and decrease at the later transplanting dates (T3, T4) and hence could not be recommended among farmers. When we consider the irrigation savings in T2 compare to T1, the irrigation savings varies with location and year, but the general tendency is that the second transplanting can save irrigation water. By considering economic (intrusion of additional rabi crop between two rice crops) and ecological factor (irrigation reduction, and hence reducing groundwater withdrawal), we recommend that the most suitable transplanting time for Boro rice should be 15th February. As such, we can effectively achieve good yield, reduce irrigation requirement, and creating opportunity for possible intrusion of addition Rabi crop between two rice crops. Overall, the findings of the present study can provide effective transplanting time and cultivar to reduce groundwater withdrawal in the present agro-ecosystem of northwestern Bangladesh and other similar areas.