Abstract

                                Zinc deficiency in flooded rice soils is considered as the most widespread and. perhaps the vital yield limting factor in maximising rice production. This zinc deficiency is caused by continued rice culture with high yielding varieties using high analysis fertilizers and also dispensing with organic manuring. Nine field experiments were carried out to study the effect of zinc application at 0, 25. 50 and 75 kg ZnSOj/ha on the grain yield and dry matter production in the representative rice soils viz. Entic Pellustorts, Entic Chromusterts, Typic Haplustalfs and. Ultic Haplustalls. The results clearly indicated that application of zinc at all levels significantly increased, the grain and total dry matter production over control. Zinc at 25 kg ZnSO./he registered higher. grain and total dry matter yields. The economic optimum doses of zinc varied between 25:8 and 45.4 kg ZnSO./ha for the responsive soils (Entic Pellusterts and Entic Chromu- sterts) of old delta of Thanjavur district, A common economic dose of 35.4 kg ZnSO/ha has been arrived at as a recommendation wherever soils are deficient in soil available.. zinc (<2:0 ppm DTPA-Zn).

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