VARIABILITY OF WATER AND SOIL CHARACTERISTICS WITHIN A PRODUCTION CYCLE IN AN ALTERNATIVE SHRIMP-PADDY CULTIVATION PLOT IN KHULNA, COASTAL BANGLADESH

Abstract

A six months study was carried out in an alternative shrimp paddy cultivation plot situated in Khulna District, Bangladesh. In soil, the mean values of sodium (Na) 13.33 mg l-1, calcium (Ca) 42.12 mg l-1, potassium (K) 472.50 mg l-1, iron (Fe) 1.01 mg l-1, phosphorus (P) 7.05 mg l-1, sulfur (S) 46.67 mg l-1, ammonium-nitrogen (NH4+-N) 247.68 mg l-1, nitrate-nitrogen (NO3--N) 114.78 mg l-1, pH 8.09, Electric conductivity (EC) 4.45 ms m-1, redox potential (Eh) -63.65 mv and organic carbon (OC) 2.56% were observed. Whereas in water, the mean values were found as Na (1051.25 mg l-1), Ca (400.00 mg l-1), K (135.50 mg l-1), Fe (0.75 mg l-1), P (1.626 mg l-1), S (283.75 mg l-1), NH4+-N (43.05 mg l-1), NO3--N (17.64 mg l-1), pH (8.29), EC (35.30 ms m-1), Eh (-73.08 mv). Except Ca and S, P, Na, K, Fe, NH4+-N, NO3--N, EC and Eh were increased over the culture period of shrimp. The value of pH was decreased gradually in water and increased in soil. Insignificant monthly variation in most of parameters measured except water Fe, soil Ca and soil NO3--N indicate that present alternative shrimp-paddy cultivation practice has no significant impact on the plot.