Effect of Shrimp-Based Cropping Systems on Salinity and Soil Fertility in a Coastal Area of Bangladesh: A Village-Level Study

Abstract

The present study analysed soil salinity and some essential soil nutrients for rice plant as affected by a shrimp-based cropping system in a coastal area of Bangladesh. The study was conducted in a village located in Satkhira district. Two main cropping systems, the shrimp-boro rice cropping system and the aman rice-boro rice cropping system, are mainly practised by local farmers in the study village. Soil and water samples were collected from the plots of these cropping systems and chemical analysis was done to measure the salinity level of the soil and water as well as to find out the nutrient status of the soil. The data was also collected for economic analysis and estimated rice and shrimp yield from the local farmers. The results revealed that the soil salinity level of the shrimp-boro rice cropping system was higher than that of aman rice-boro over the consecutive years of 2010, 2011 and 2012. The soil was found to be moderately saline. The organic matter content, potassium, calcium, magnesium and sulphur levels of the soil in the shrimp-boro rice system were increased, while the total nitrogen, phosphorus, boron and zinc availability decreased. It was also found that the yield of boro rice was 4,950 kg/ha whereas the aman rice yield was 3,020 kg/ha and that for shrimp the yield was calculated as 268 kg/ha for one growing season (six months). The total income from boro rice, aman rice and shrimp was calculated as 127,760 Tk, 87,118 Tk and 149,476 Tk, respectively. The paper concludes that although some nutrient elements were available in adequate amounts, salinity kept these nutrients from being taken up by the rice plants since salinity changes the osmotic pressure of the soil solution system. This may ultimately lead to a reduction in rice yield and threaten the sustainability of the local shrimp-boro rice cropping system.

Modeling daily soil salinity dynamics in response to agricultural and environmental changes in coastal Bangladesh

“…To build confidence on the proposed soil salinity model reproducing the temporal variability of the soil salinity, we have compared the model results against the soil salinity observations reported by [ Rahman et al ., ] under Aman rice and shrimp farming at village level in Satkhira district and the observations of Mondal et al . [] at two villages in Khulna district.…”

“…The proposed soil salinity model can reproduce the observed inter‐annual variability reported by [ Rahman et al , ] for combined Aman rice and Bagda shrimp farming during the period 2010–2012.…”

“…To build confidence on the proposed soil salinity model reproducing the temporal variability of the soil salinity, we have compared the model results against the soil salinity observations reported by [Rahman et al, 2013] under Aman rice and shrimp farming at village level in Satkhira district and the observations of Mondal et al [2001] temperature and rainfall at Satkhira and Khulna stations against the weather ensembles shows that ensemble Q8 is the closest to the observations, but the daily temperature for the climate ensembles used in soil salinity calculations tends to systematically over-estimate the maximum monthly observed temperatures and under-estimate the lowest temperatures ( Figure S2). Rainfall is well within the observed range with some year to year and inter-climate ensembles variability.…”

“…Step salinity increases during the Bagda raising period are due to pond recharges to maintain the desired pond water depth. Because Rahman et al [2013] did not reported the area coverage dedicated to shrimp and rice, an assumption must be made to be able to compare the model with the observed soil salinity. Two area averaged soil salinity values are calculated: one value assuming shrimp and rice area are equal (i.e., 50% weight for each crop) and other assuming rice area is slightly larger than shrimp area (70% rice and 30% shrimp).…”

Land Use Management in Disaster Risk Reduction

“…A study conducted by Rahman et al ( 2013a ) clearly noticed that cropland is decreased due to increases in shrimp culture. Due to these changes in land use, the yield of the aman rice crop declined quickly.…”