Abstract
The results of a field experiment conducted for six years on laterite soil showed that single superphosphate, ammonium phosphate, nitrophosphate and rock phosphate had similar effects on the yield of nuts palm yr-1. However, when percentage yield increase over pretreatment yield was computed, rock phosphate proved best, followed by ammonium phosphate. Regression analysis revealed an optimum interaction between soil available P and leaf P for rock phosphate. The soil available P increased with the increase in the levels of P applied. Nitrophosphate increased the soil available P to a maximum, followed by ammonium phosphate, single superphosphate and rock phosphate. Fertilizer-P application generally reduced soil pH which was most marked with ammonium phosphate. The treatments showed marginal mobility of P to the subsoil which has been attributed to mechanical movement as a result of cultural operations in the coconut basin. Higher levels of applied P influenced the leaf P values which were not reflected in the yield. Costs of fertilizer indicated that rock phosphate as a P-carrier is cheapest.
