Direct effect of phosphorus and potassium fertilizers and farm yard manure on potato and their residual effect on cheena and maize

A field experiment was conducted during 1976–79 in alluvial soil at Central Potato Research Station, Patna, to study the effect of different levels of P (0, 20 and 40 kg/ha) and K (0, 40, 80 kg/ha) in all combinations, along with farmyard manure (15 and 30 tons/ha) applied to potato each year in a potato-cheena-maize crop rotation. Potato tuber yield was increased significantly by application of K alone and in combiiiation with P. The response was of linear nature. The K application at the rate of 80 kg/ha had pronounced residual effect on cheena and significant residual effect on maize crop. Application of P alone and in combination with K had little direct effect on potato and residual effect on cheena and maize. Farmyard manure application at both the levels had significant effect on tuber yield and the response was linear. Its residual effect was significant on the maize crop 30 ton farmyard manure/ha was able to meet P and K needs of potato and other crops in rotation and maintain available P status of the soil. Application of 40 kg P/ha from fertilizers conld not maintain the available P and K status of the soil at the initial level but it was significantly better than the control.