) rock phosphate in very fine size (say 80% finer than 54 microns). Needless to say, the finer the rock phosphate the better is the agronomic efficiency of PROM. The best results were obtained on the filed using 3 to 4 tonnes of compost or farmyard manure that contained minimum of 200 Kg rock phosphate or a higher dose as recommended by the agricultural scientists depending on the soil conditions. Addition of phosphate solubilising bacteria improves the efficiency of PROM. Phospho-compost technology developed by Indian Council of Agricultural Research (ICAR) is similar to PROM and the difference is that low grade (+18% P2
) rock phosphates are also allowed to make phospho-compost. M/s Rajasthan State Mines & Minerals Limited initiated and independently funded research work on PROM.
A variety of organic materials can be used in the process of composting such as dung, agricultural crop wastes, press mud from sugar industry, solid wastes from fruit juice industry, oil cakes, waste from wool industry etc . While composting these organic materials it should be ensured that C: N ratio is at 30:1 and the best will be at 20:1 at the end of composting process.
It is interesting to note that ancient Indian text “Vrikhayurveda” (meaning, health science of trees or plants) written by Surapala mentions a preparation “Kanupa” which is a compost consisting of animal bones. Even today animal bones are a good replacement for rock phosphate.