Effect of Soil and Water Salinity on Dry Season Boro Rice Production in the South-Central Coastal Area of Bangladesh

Abstract

Salinity is considered one of the main challenges for agriculture in the coastal zone of Bangladesh. However, soil and water salinity levels vary with location and time of the year. How these seasonally variable salinity levels affect crop production is unclear. We examined the impacts of spatio-temporal variation of soil and water salinity on boro rice production in the south-central coast of Bangladesh. We divided the study areas into three zones (low, moderate, and high salinity) based on the distance from the sea (km). We measured soil and river water salinity (inside and outside the polders) for eight months from November 2020 to June 2021. From March- April 2021, we collected comprehensive water samples from different canals and crop fields. The groundwater levels, soil parameters (physical and chemical), and salt-tolerant boro rice varieties yield data were collected from secondary sources. The observed and collected data were calibrated and validated using the SWAP-WOFOST (an acronym for Soil Water Atmosphere Plant – WOrld FOod STudies) model. The result showed that salinity and groundwater levels vary with time and space. In addition, soil salinity levels and boro rice yield vary with soil texture classes. We found the spatial variations of boro rice yield. Near the seafront regions (high salinity zone) yields are much lower than in other coastal regions. In order to get the highest actual yield from boro rice in high salinity areas, it should be sowed around fifteen days earlier than the currently recommended date and cultivated inside the polder. Although boro rice is not much affected by salinity in the moderate and low salinity zones, early sown gives the more yield (longer radiation capture) than the current practice. Altogether, the findings of this study will help the stakeholder to formulate crop-level adaptation plans and policy-making in the south-central coastal districts.

Keywords: Salinity, Boro rice, SWAP-WOFOST model, Bangladesh