Relationship between salinity and crop production in different hydrological regimes downstream of Muhuri regulator

Abstract

A large landmass was formed at the downstream ofFeni river duc to the construction ofMuhuri regulator at a cross dam in Mirsarai upazila of Chittagong district. But this land is more vulnerable to storm and tidal surges leading to saline water intrusion. Thc study site was selected from this area to investigate the relationship between salinity and crop production. Soil samples were collected from different hydrological regimcs such as old protected area, new protected area, unprotected area and affected area. Samples were taken from topsoil, subsoil and substratum at each location in both aman and rabi seasons. Crop yield of the sampling plots were recorded through farmer's interview. It was fonnd that, salinity of study area was less than 4 dS/m both in aman and rabi seasons. Rice is a semi-tolerant crop (can tolerate salinity up to 4 dS/m), so no significant relationship between soil salinity and rice yield was found in aman season. In rabi season, salinity was also found less than 4 dS/m except in unprotected area. A positive correlation was found between soil salinity and khcsari yield, which was found to be significant in unprotected area Water sallnity inside the cross dam was around 0.1 dS/m (rabi season), which is considered excellent for irrigation. But outside the cross dam it ranged in between 4.8-5.4 dS/m in aman scason and 12.4-20.8 dSJm in mhi sea'illn,which was extremely toxic for irrigation. Although soil salinity permits HYV rice cultivation in aman season, water logging was reported by fanners as the main constraint to HYV rice cultivation in the study area. The fwmers opined that HYV rice in aman season can be cultivated by imprming water logging problems of Godashara canal in old protected area, by removing boundaries of fish pond in new protected area, construction of an embankment on the eastern side of Feni river in unprotected area and cultivating submergence tolerant variety in affected area. HYV rice in boro season can be cultivated in old and new protected area by utilizing Feni river water inside the Muhuri reb'lliatorand e10suredam for irrigation purpose. But it can not be cultivated due to salinity problem ("4 dS/m) in unprotected area and lack of irrigation water in affected area. But in these areas khesari can be grown successfully by utilizing residual soil moisture.