Abstract

                                Radio-tracer studies have shown that only 10-20% of the phosphate applied as fertilizer is utilised by crops. With reference to paddy the application of phosphate through a preceding green manure crop has been considered of some value. Sen and Sunder Rao (1952) reported that in Bihar, phosphate manuring of daincha for green manuring paddy showed marked increase in yields of both green manure and paddy crop. In Mysore, sunnhemp in conjunction with superphosphate gave marked increases in yields of both green manure and succeeding paddy. Relwani and Ganguli (1959) working on Punjab soils have reported no beneficial effects due to application of phosphate through a green manure for paddy. Work done at Coimbatore during 1954-57 (Anon, 1954-55, 1955-56, 1956-57) did not show any beneficial effect of indirect application over direct application of phosphate for improving the paddy yields. The variations in results in these experiments have been attributed to the differences in the phosphorus fertility status of the soils. No evidence is available with reference to the utilisation of the applied phosphate under the direct and indirect methods of application of phosphate. This study, therefore, aims at finding out the efficiency of the superphosphate utilisation by the paddy crop under the direct and indirect methods, using radio-tracer technique.

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