Abstract

The mud balls prepared from an admixture of soil and urea or ammonium sulphate, with and without carbonaceous material, were tested for loss of N through ammonia volatilization during sun-drying and transformation in flooded soil. During sun-drying, the mud balls, particularly those prepared from powdered rice straw and urea, lost as much as 26% of the fertilizer N through ammonia volatilization. Addition of small quantities of super phosphate or neem oil- extract effectively reduced this loss. The average dissolution rate of mud balls in soil was about 5% in 10 weeks. Laboratory incubation of 15 N-labelled mud balls revealed initial immobilization of fertilizer N which varied depending upon the presence and decomposibility of added carbonaceous residue. It is suggested that subsequent remineralization may result in an overall slow-release effect.

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