Brackish Water for Irrigation: III Effects on Yields of Crops in Wheat-Rice Rotation and Properties of the Bhalike Soil Series

摘要

Deterioration of soil health and reduction in plant growth are characteristics of long-term irrigation with brackish waters. In the present investigations, we evaluated the effects of such waters on the declining rate of wheat and paddy yields and properties of the Bhalike soil series for four and a half years. Five levels, each of EC, SAR and RSC at 0.65, 2.0, 4.0, 6.0, 7.35 dS m^-1; 3.95, 9.65, 18.0, 26.35 and 32.04 (mmol L^-1)^1/2 and 0.65, 2.0, 4.0, 6.0, 7.35 mmol_c L^-1, respectively, were applied to 30 x 68 cm undisturbed and disturbed soil columns taken in metallic cylinders (30 x 76 cm). Results indicate that brackish water with an EC_iw of ≤ 4.0 and 4.0 dS m^-1; SAR_iw ≤ 9.65 and 18.0; RSC ≤ 4.0 and 4.0 mmol_c L^-1 may be used for irrigation of wheat without yield reduction up to coded ?-1.682, -1 and 0? levels of SAR_iw and RSC; EC_iw and RSC; EC_iw and SAR_iw, respectively, for the undisturbed and disturbed soil columns. Paddy yield decreased linearly with EC_iw at given levels of SAR_iw and RSC. The SAR_iw up to 26.35 at coded ?-1.682 and ?1? levels of EC_iw and RSC did not affect the paddy yield in both the undisturbed and disturbed soils. At higher coded ?0, 1 and 1.682? levels of EC_iw and RSC, the SAR_iw became narrow, i.e. 9.65 for paddy yield. The RSC up to 2.0 and 4.0 mmol_c L^-1 were observed safe for paddy yield in the undisturbed and disturbed soils, respectively. The rate of yield reduction with similar EC_iw, SAR_iw and/or RSC was high in the undisturbed than that in the disturbed soils. Higher grain and paddy yields were predicted in the disturbed than that in the undisturbed soil columns with the same levels of EC_iw, SAR_iw and RSC. The soil EC and SAR tended to increase with EC_iw, SAR_iw and/or RSC, with exception to EC_e which decreased with RSC waters. However, the rate of increase in EC_e and SAR was high with EC_iw and SAR_iw particularly at higher levels of SAR_iw and RSC; EC_iw and RSC. It was observed that whole of the undisturbed and disturbed soil profile attained EC_e >4.0 dS m^-1 and SAR values >13.3 which are the upper limits for saline-sodic soils. The bulk density (BD) decreased by 4.9 and 4.4 %, respectively, for the undisturbed and disturbed soils with EC_iw, 7.35 dS m^-1 over EC_iw 0.64 dS m^-1 at coded ?0? levels of SAR_iw and/or RSC of waters. The BD was 18.1, 9.3 and 14.3; 9.5 %, respectively, with SAR_iw 32.04 and RSC 7.35 mmol_c L^-1 over SAR_iw 3.95 and RSC 0.64 mmol_c L^-1for the undisturbed and disturbed soils. The increase in K_s was 0.048, 0.118, 0.172 and 0.190; 0.043, 0.109, 0.170 and 0.197 cm h^-1, respectively, with EC_iw 2.0, 4.0, 6.0 and 7.35 dS m^-1 over EC_iw 0.64 for the undisturbed and disturbed soils. At given levels of EC_iw and RSC; EC_iw and SAR_iw, the SAR_iw and RSC reduced the K_s of the soils. For instance, reduction in K_s was 0.003, 0.036 and 0.069 cm h^-1; 0.01, 0.042 and 0.071 cm h^-1 with SAR_iw 18.0, 26.35 and 32.04, respectively, over SAR_iw 3.95 at coded ?0? levels of EC_iw and SAR_iw [4.0 dS m^-1 and 18.0 (mmol L^-1)^1/2]. At coded ?0? levels of EC_iw and SAR_iw, the RSC waters up to 2.0 mmol_c L^-1 increased the K_s of both the soils.