Assessment of soil salinity and its impact on agriculture after the cyclone SIDR

Abstract

Sarankhola lJpazila in Bagerhat district was severely affected by cyclone SJDR. Preliminary investigations showed that the salinity level of soil was increased which affected the cropping and fishing practices in the region. Some of the coastal polders havc also been damaged during the cyclone event. Farmers were forced to change their cropping practices at the post cyclone stage. In the present study, change in soil salinity after the cyclone and its impact on agriculture is being investigated in the study area. Soil samples were collected from all the unions of highly affected areas of Bagerhat district. Samples were taken from topsoil after cyclone SIDR and both from topsoil and subsoil after the monsoon of 2008. Crop yield of the sampling plots were recorded through farmer's interview. General information was collected through Focus Group Discussion (FGD). From the analysis ofsoi! salinity after cyclone SIDR, results show that in Rayenda union, which was inside polder, soil salinity varied from 1.11 dS/m to 1.93 dS/m while in Southkhali union soil salinity varied from 2.72 dS/m to 4.7 dS/m inside polders and 4.87 dS/m outside polders. Samples from Dhansagor union, which is inside polder but was inundated during the stonn surge show salinity more than 6 dS/m. Samples from Khontakata union, which is inside polders, show soil salinity 4.4 dS/ro. Most of the soil samples were basic in nature. After the monsoon the soil samples were also analyzed for both topsoil and subsolJ of same sampling plots. The soil salinity of every sampling plot was reduced after the monsoon. The soil salinity reduced hy 76.6, 46.6 and 19.3 percent in the Rayenda union. In the Southkhali union, it reduced by 49.1, 31.5 and 72.6 percent. In Dhansagor and Khontakata union it reduced by 84.0 and 77.9 percent respectively. It was observed that particle size as well as soil pH influences the salinity reduction. Coarser particle size enhances soil salinity reduction; on the other hand higher soil pH restricts salinity reduction. The yield of Arnan in 2008 season was reduced by as high as 63 percent compared to previous average yield. Local T. Aman was cultivated in the all-respective plots of the study area. The soil salinity and some other factors contributed to yield reduction. In Jilbunia village of Rayend a union, the average yield of Aman crop before the smR was 1.94 ton!ba, but it was decreased after the SmR, which turned into 1.38 tonlha. About 29 percent yield was decreased. In another two villages of Rayenda union, at Lakurtola and at Rajeshor, production decreased by 63 percent and 32 percent respectively. In Southkhali union there were three sampling plots named N. Southkhali, Gabtola (inside polder) and Gabtola (outside polder). The yield of AmllIl crop during monsoon decreased in the first two plots by 43 percent and 41 percent respectively. No crop was cultivated in the outside polder ofGabtola sampling area during the 2008 monsoon. In Rajapur village of Dhansagor union and in the N. Khontakata ofKhontakata union the yield decreased by 50 percent and 41 percent, respectively. It was also found that not only soil salinity contributed to yield reduction, but also other factors like lack of irrigation water at the grain formation stage, low quality of seeds and pests were the likely reasons behind yield reduction.