Relationship Between Salinity and Crop Production in Different Hydrological Regimes Downstream of Muhuri Regulator

Abstract

A large landmass was formed at the downstream of Feni river due to the construction of Muhuri regulator at a cross dam in Mirsaraiupazila of Chittagong district. But this land is more vulnerable to storm and tidal surges leading to saline water intrusion. The study site was selected from this area to investigate the relationship between salinity and crop production. Soil samples were collected from different hydrological regimes such as old protected area, new protected area, unprotected area and affected area from topsoil, subsoil and substratum in both wet and dry period. Crop yield of the sampling plots were recorded through farmer’s interview. It was found that, salinity of the study area was less than 4 dS/m both in aman and rabi season. Rice is a semi-tolerant crop (it can tolerate salinity up to 4 dS/m). So no significant relationship between soil salinity and rice yield was observed. Farmers of this area mainly cultivate khesari crop in rabi season. A significant positive correlation (correlation coefficient 0.97) was found between the soil salinity and khesari yield in unprotected area. Water salinity 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 season and 12.4-20.8 dS/m in rabi season, which was extremely toxic for irrigation for the cultivation boro rice. Although soil salinity permits to cultivate HYV rice in a man season but water logging is the main constraint. HYV rice in boro season can be cultivated in old and new protected area by utilizing Feni river water inside the Muhuri regulator and closure dam for irrigation purpose. But in unprotected area, it can not be cultivated due lack of suitable irrigation water and tidal flooding. In the study area, non-irrigated crop like khesari can be grown successfully just after aman season by utilizing residual soil moisture.