Effect of soil and water salinity on dry season boro rice production in the south-central coastal area of Bangladesh.

Salinity varies with location and time of the year. It can significantly impact crop production. The level of negative impacts depends on the salt concentration and time of its occurrence, which, however, has not been studied for many crops, especially for rice grown in the coastal area of Bangladesh. Our study explored the impact of spatio-temporal fluctuations in soil and water salinity on boro rice production in the south-central coast of Bangladesh. Here, we simulated the soil salinity from November 2020 to May 2021 for fourteen locations classes using the SWAP-WOFOST model. The model was calibrated and validated with measured secondary data. Next, the yield of two salt-tolerant boro rice varieties (BRRI dhan47 and BRRI dhan67) was simulated using the customized soil, weather, and crop data. We also simulated the yield by adopting agronomic management practices (i.e., changing planting time and using fresh irrigation water). Our results showed that salinity levels varied with different soil textural classes, soil depth, location, and time of the year, and that had a significant influence on boro rice production, giving spatial variability. Specifically, boro rice had a higher yield in coarse texture soil than in fine texture soil. Simulated yields in areas proximate to the sea ranged from 668 to 1239 kg ha-1, yields that are significantly lower than those simulated in moderate (2098-4843 kg ha-1) and low salinity zones (4213-4843 kg ha-1). Moreover, the simulation of yield with sowing/planting rice earlier by fifteen days provided a higher yield than the current planting practice since it could avoid salinity at later stages of growth. For a similar reason, growing rice inside the polder provided a higher yield than outside the polder. The insights gained from our study carry significant implications for contemporary crop-level adaptation strategies and policy-making in coastal districts.