Effect of levels of N, P, K and Mg fertilizers on yield of oil palms

Study on effects of nitrogen, phosphorus, potassium and magnesium as single fertilizer on yield was conducted with 7-10 years old oil palm. The oil palms were transplanted in October 1985 on sandyloam soil at Surat Thani Horticultural Research Center. The design of the experiment was RCB with 5 replications and 10 treatments that composed of each level of fertilizers as follow; ammonium sulfate, triple super phosphate, potassium chloride, and kieserite. The treatments were 0-0-0-0, 1.5-1-3-0, 3-1-3-0, 4.5-1-3-0, 1.5-0.5-3-0, 1.5-1.5-3-0, 1.5-1-1.5-0, 1.5-1-4.5-0, 1.5-1-3-0.5 and 1.5-1-3-1 kg/palm/year. The investigation revealed that average fresh fruit bunch (yield) of all fertilizer plot sincreased 64.6 percent compared with no fertilizer plot. In addition, fertilizer at the rates of 3-1-3-0 and 1.5-1-3-0.5 kg/palm/year gave the highest yield of 141.3 kg/palm/year (3.22 tons/rai/year). The study found significant relationships between N and P concentrations in leaf, bunch number, bunch weight and fresh fruit bunch. Moreover, the investigation also found relationships between K and Mg concentrations in leaf, bunch weight and fresh fruit bunch. From the relationship equations, the critical concentrations of each oil palm plant nutrition were N= 2.51 percent, P = 0.159 percent, K = 0.885 percent and Mg = 0.23 percent. These values can be recommended for oil palm growing in sandy loam soils under the East Coast of southern environmental conditions.