The Value of Farmyard Manure as a Source of P and K for Potato

Field experiments were conducted at the Central Potato Research Institute, Simla to study the cumulative, direct and residual effect of FYM on the potato. In the direct effect, FYM applied å 44 kg P/ha was as effective as superphosphate in increasing the yield of tubers but was less effective than the combined application of 44 kg P and 125 kg K/ha. However, FYM in the cumulative effect produced higher yield than the combined application of P and K as inorganics. The residual effect of FYM was quite substantial and was higher in a low rainfall year. On the other hand, the residual effect of PK-fertilizers was not discernible. Past applications of FYM were more effective in maintaining yield levels than the inorganic P source as judged from the lower responses of potatoes to fresh application of P. FYM was intermediate in building up available soil P as compared to 44 and 88 kg P/ha as superphosphate, while it was having an edge over potassic fertilizer in improving available soil K. Application of P alone resulted in the depletion of the soil K.