摘要 : A field experiment was conducted with rice in Zn deficient soil to study the direct, residual and cumulative effects of Zn. Soil application of ZnSO4 increased the grain yield of rice. Application of 75 kg zinc sulfate (50 kg init... 展开 A field experiment was conducted with rice in Zn deficient soil to study the direct, residual and cumulative effects of Zn. Soil application of ZnSO4 increased the grain yield of rice. Application of 75 kg zinc sulfate (50 kg initially and 25 kg at5th season) gave the highest cumulative (eight seasons response) effect. The yield increase was 5.1 t/ha over control. Application of 12.5 kg ZnSO4/ha in Zn deficient soil is not sufficient to get optimum yields. Farmyard manure did not substantially increase the yields compared to zinc sulfate application. Zinc content in the index leaf samples increased with the increase in the ZnSO4 application. Zinc content remained above the critical level even after seven seasons in the treatments, where ZnSO4 wasapplied initially, indicating that ZnSO4 has got strong residual effects. Soil available zinc after the harvest of each season crop indicated strong residual effects. The uptake in the zinc sulfate treated plots was significantly more than the control plot. 收起