Phosphorus-Zinc Interaction for Soybean Production in Soil Developed on Charnockite in Ekiti State

The soils derived from charnockite in Ekiti State Nigeria were found to be low in zinc and phosphorus. This study was therefore, conducted during the rainy seasons of 2006 and 2007 to evaluate growth and yield response of soybean TGX-1440LE from the direct effect and interaction of phosphorus and zinc. Treatments consisted of factorial combination of 2 levels of P (0 and 30 kg P ha-1), three levels of Zn (0, 2 and 4 kg ZnSO4 ha-1) in a randomized complete block design in a soil developed in charnockite in Ekiti State the growth data were collected at 2 weekly intervals while yield components were taken at harvest. Stem girth, number of nodules and nodule weight significantly (p<0.05) increased with 2 kg Zn ha-1 application, which gave 111.2% yield advantage over the control treatment (0 kg Zn ha-1). Fertilizer rate above 2 kg Zn ha-1 significantly (p<0.05) decreased P uptake. The 30 kg P ha-1 rate produced better growth which was not significantly different from 0 kg P ha-1 while increase in P and Zn uptake was significant. The PxZn interaction was significant for grain yield and Zn uptake. The treatment combination that gave the highest yield was 30 kg P ha-1 and 2 kg Zn ha-1.