During 1990–95 in studies in lysimeters (1.8 m deep, 0.9 mill) filled uniformly with a silt loam soil (Typic Haplustalf), the soil pH increased initially and stabilized after 3 years of irrigation with sodic waters whereas sodicity and salinity continued to increase during the experimental period. The mean SAR. and ECw. (0–0.6 m soil) after 5 years of irrigation were 1.05 adj. RNa and 1.45 ECw, respectively, with higher ECwaters causing greater deterioration. Yields of both cotton and wheat remained unaffected by water quality during the initial 4 years. However, during the 5th year, wheat yields reduced (4–30%) with increase in SARw and RSC especially at ECw 4.0 dS m−1. Residual alkalinity either due to HCO3 or HCO3 and CO3 had similar effects. The results indicate that cotton-wheat crops can be irrigated with waters having EC 2–4 dS m−1 and SAR ≤ 30 and RSC ≤ 10 me L−1 for 4 years under well drained soil and 750 mm rainfall conditions.
Sodic irrigation, ionic effects, soil degradation, cotton-wheat
