Effectiveness of calcined rock phosphate and leucaena prunings as a source of nutrients for maize in a tropical soil

Cost reduction and an increased efficiency in the utilization of nutrients are essential for establishing agricultural systems in the tropics. The combined effects of calcined Al phosphate (ALP) and leucaena prunings (L) on the agronomic efficiency and on the efficiency of physiological use of nitrogen (N) and phosphorus (P) in maize were assessed. The treatments consisted of 160kgha(1) of P2O5 from ALP and 100kgha(1) of N from urea (ALP+U); 160kgha(1) of P2O5 from ALP and 6Mgha(1) of L (ALP+L); 160kgha(1) of P2O5 from single superphosphate (SSP) and 100kgha(1) of N from U (SSP+U); 160kgha(1) of P2O5 from SSP and 6Mgha(1)of L (SSP+L); and a control without fertilization. The decreasing order of effectiveness among treatments was SSP+L>ALP+L>SSP+U>ALP+U>control. Both leucaenaphosphate combinations had beneficial effects on the growth of the maize, the N and P recovery, and the agronomic efficiencies. Both ear weight and grain weight were higher under the SSP+L treatment than under the SSP+U treatment and higher under the ALP+L treatment than under the ALP+U treatment. The low N and P agronomic efficiency in maize grown under the ALP+U treatment made the combined use of these fertilizers undesirable. The satisfactory efficiency of grain production shown by the maize grown under ALP+L indicated that this treatment could replace processed fertilizers for use in agrosystems management in the tropics.