No abstract

A greenhouse experiment was conducted with 20 soils representing semiarid soils of Coimbatore district to peredict the most reliable soil test method for determining the available Zn status in the soil. Therewere four levels of Za (0, 2.5, 5.0 and 7.5 ppm) and cach treatment was replicated two times. Maize (Ganga 5) was used as the test crop and the crop was allowed to grow for seven weeks. The results showed that among the six extractants tried, EDTA + (NH4)2 CO3 and DTPA were found to be the most reliable soil test methods as compared to the other four methods employed. Between the two methods, DTPA soil test method could be recommended for determining the available Zn status in the soils of Coimbatore district as it had given higher relationship with the actual yield, Bray's per cent yield, Zn content in leaves and leaf sheath and stem

Soybean Co.l. raised on Perianaickanpalayam (Typic ustivertept) and Irugur (Typic ustorthent) soil scries at Tamil Nadu Agricultural University Farm, Coimbatore during rabi 1990-91 and kharif 1991-92 respectively responded significantly to Zn fertilizetion at 5.0 kg ha. Combined application of Zn, Mo and FYM at 2.5 kg, 0.5 kg and 10 t ha respectively produced the highest seed yield in both the years besides increasing their content and uptake by soybean seed. The highest Fe uptake by seed during rabi 1990-91 was evidenced with the application of 5.0 kg Zn ha".

Field experiments were conducted on red soils (Typic Ustorthent) at the Tamil Nadu Agricultural University Farm of Agricultural Research Station, Bhavanisagar to study direct, residual and cumulative effect of applied Zn to IR 20 rice. The continuous application of ZnSO4 at 25 kg per ha for every season of rice crop significantly increased grain and straw yield and resulted in 17 per cent increase in grain yield over NPK treated control. Application of ZnSO4 at 50 kg for first crop resulted in residual effect of Zn with increase in the grain yield of two subsequent crops. Similar trend was also observed for the level of 75 kg ZnSO4/ha. Residual effect of ZnSO4 application at 100 kg/ha to first crop was observed for five subsequent rice crops.

The efficacy of organic amendments (pressmud and zinc enriched pressmud) and zinc fertilisation was studied in paper factory effluent imigated soil. The results showed that available phosphorus content in soil and its uptake in plant were increased due to the application of pressmud. Application of amendments and ZnSO4 significantly increased exchangeable calcium, but decreased the exchangeable sodium. Total day matter production was significantly enhanced by the application of pressmud and soil application of ZnSO4. Enrichment of pressmud with ZnSO4 resulted in increased dry matter production. Foliar spray of zinc at 0.5 per centconcentration given at 90 and 110 days after planting significantly increased the dry matter production over soil application of zinc and control.