Determination of optimum rate of phosphorus and potassium fertilizers for a four-year-old oil palm (Elaeis guineensis Jacq.)

Appropriate fertilizing rate of phosphorus (P) and potassium (K) plays an important role to increase growth and yield of oil palm as well as to minimize environmental pollution because of the residues of inorganic fertilizer. This study aimed to explain the effect of P and K fertilizers and determine the optimum rate for a four-year-old oil palm. Experimental design used in each of these experiments were one factor of randomized complete block design factor and consisted of five levels with three replications. The treatment levels used in experiment 1 were 0, 443.75, 887.5, 1331.25, and 1775 g P2O5 per palm per year. The treatment levels used in experiment 2 were 0, 1020.6, 2041.2, 3061.8, and 4082.4 g K2O per palm per year. Application of P fertilizer significantly affected to palm height, trunk girth, stomatal density, leaf P content, bunch number and yield of FFB. The optimum rate of P fertilizer was 924 +/- 88 g P2O5 per palm per year. Application of K fertilizer significantly affected to trunk girth, leaf area of frond 17, stomatal density, leaf K content, bunch number and yield of FFB. The optimum rate of K fertilizer was 2760 +/- 107 g K2O per palm per year.