Slow Release And Amended Nitrogenous Fertilizers

The available research results clearly indicate that crops remove only a part of applied nitrogen (N), the recoveries being fairly low in tropical zone with a heavy rainfall. Reports on the evaluation of slow release and amended nitrogenous fertilizers, although a few, are encouraging. A study of economic feasibility of the use of these materials has not been possible, since most of these materials are still in the developmental stage and are being produced on a pilot plant basis. Needless to add that commercial and pilot plant costs are far apart. However, we do not foresee any great increase in the use of the presently available controlled release fertilizers unless some major technological advance makes them available at a much lower cost. It is important to continue development of new materials utilizing the controlled release concept. The authors are of the opinion that the blending cost of the N-fertilizer with the nitrification retarders should not exceed much over 12-15% surcharge on N cost. Similarly slow release N-fertilizers should be available at a similar price.