Rice production in Sri Lanka has increased considerably during the last three decades as a result of cultivation of high yielding varieties, increase in the area of cultivation under irrigation and heavy use of plant nutrients. Most of the high yielding varieties which are extensively grown throughout the country require recommended levels of fertilizers in order to obtain their potential yields. Therefore, effective and efficient way of fertilizer application is important. Coated fertilizers are widely used to improve the efficiency of fertilizer application. However, the conventional coated fertilizers such as sulphur coated urea and urea super granules are not popular among the rice farmers in Sri Lanka owing to high cost of the coated fertilizers. One of the most sustainable solutions is application of paddy husk charcoal as a coating material to N fertilizer so as to gradually release nitrogenous compounds and making them available for plants. Objectives of this study were to evaluate total N, P K and organic matter of soil amended with paddy husk charcoal coated urea and to compare the yield of paddy production. A field experiment was carried out at Kalugamuwa farmer field in Yala 2010 and Maha 2010/2011. The field was divided into three blocks of equal size (30 m x 5 m) and each block was further subdivided into four plots (5 m x 5 m) and treatments were arranged in randomized complete block design. Treatments were application of (1) chemical fertilizer only, (2) urea coated charcoal only (1/3 of recommended urea) (3) chemical fertilizer and paddy straw compost (compost obtained from anaerobic digestion of paddy straw) and (4) paddy straw compost and urea coated charcoal only. The highest mean grain yield of 12.59kg/plot was obtained with the application of chemical fertilizer followed by charcoal coated urea with compost, chemical fertilizer and charcoal coated urea only for Yala season. Paddy husk charcoal coated urea can potentially be used as a slow releasing nitrogen fertilizer which reduces leaching losses of urea. In addition, coating is less costly and helps reducing the fertilizer cost (70% of urea cost) and contribute to mitigate atmospheric pollution as well as pollution of water bodies
