Water and Soil Salinity Dynamics and Dry Season Crop Cultivation in Coastal Region of Bangladesh

Abstract

Coastal region has a potentiality of crop intensification through introduction of dry season crops. This study aimed to determine the possibility of dry season crop cultivation through water resources management. Water salinity of two rivers named Jabjapia at Dacope, Khulna and Andharmanik at Amtali, Barguna was monitored during 2017 to 2018. River water was trapped into adjacent canals during mid-December. Salinity of trapped water, field water and soil were recorded weekly. Groundwater depth and salinity were monitored from installed observation well near to field. Salt tolerant rice varieties BRRI dhan67 and BINA dhan10 along with popular BRRI dhan28 and BRRI dhan58 were cultivated. Rabi crops like sunflower, maize, sweet gourd (pumpkin) and water melon were also cultivated. River water salinity remained below 4.0 dS m^-1 up to 15^th of December in both locations and then rose sharply. So, 10-15 December is the suitable time to trap river water into the canal. Salinity of trapped water remained in permissible limit for irrigation both at Dacope (1.30 to 3.00 dS m^-1) and Amtali (1.1 to 2.3 dS m^-1) during boro season. Although groundwater salinity at Dacope (2.30 to 3.52 dS m^-1) was comparatively less than Amtali (3.12 to 11.7 dS m^-1), it was not suggested for irrigation. Observed maximum water salinity in rice field was 3.14 and 2.9 dS m^-1 in April at Dacope and Amtali, respectively. BRRI dhan67 and BINA dhan10 gave similar average grain yield of 6.4 and 6.2 t ha^-1, respectively at Dacope. Similar yield trend was found at Amtali. Among the tested rabi crops sweet gourd gave the highest maize equivalent yield of 9.67 t ha^-1 at Dacope. Since coastal regions have large river and canal network, there is a good prospect to increase cropping intensity by introducing salt tolerant varieties and trapping water having recommended salinity level for irrigation.