Effect of Farmyard Manure and P Application to Potato on Available P and Crop Yield of Potato (Solanum tuberosum)-Sunflower (Helianthus annuus) Sequence

A field experiment was conducted on a loamy sand soil for five years to evaluate the effect of farmyard manure (FYM) at 0 and 50t ha−1 and P levels (0, 13, 26 and 39 kg P ha−1) on the yield of potato tuber and succeeding sunflower and build up of available P in soil. Application of FYM at 50 t ha−1 caused substantial improvement in tuber yield (29%) and P uptake (26%) of potato, seed yield of sunflower (14.7%), sustainable yield index of potato and available P content of soil. Response to P application to potato was significant up to 13 kg P ha−1 both in the presence and absence of FYM but fertilizer P efficiency was greater in no-FYM as compared to FYM treatment. For obtaining optimum potato and sunflower yield and maintenance of available P content of soil on sustainable basis, application of 13 and 26 kg P ha−1 to potato in the presence and absence of FYM, respectively, seem to be sufficient.