Phosphorus Content of an Acid Soil and Sweetpotato Uptake as Affected by Nitrogen Application

A pot experiment was conducted to study the changes in P content of acid soil as affeced by different N levels and sweetpotato uptake. Thirty cm healthy cuttings of VSP-2 sweetpotato were planted in clay pots filled with 10 kg soil acid soil. These were applied with 45, 90, 135 and 180 kg N/ha applied at five planting intervals as follows: T1- all at plantingl T2 - all at one month after planting; T3 - 1/2 at planting and 1/2 at one month after planting; T4 - 1/2 at planting and 1/2 at two months after planting at T5 - 1/3 at planting, 1/3 at one month after planting and 1/3 at two months after planting. Application of N fertilziers enchanced the availability of added inorganic P in acid soil and the P uptake of sweetpotato. Reduction in P content of acid soil was observed at different stages of plant growth and this was most evident at harvest. An exponential relationship was established between P removed from acid soil at harvest and root yield, emphasizing the important role played by phosphorus aside from N and K in root growth and formation of sweetpotato.