Prakit Tongkum, Wanna Leowarin, Chairatna Nilnond, Theera Eksomtramage, and Theerapong Juntaraniyom

pp. 649 - 659

Abstract

The effects of fertilizer application rates on leaf nutrient contents and yield of oil palm were investigated at the Agricultural and Technological College Plantation in Trang province during May 1998 - June
2001. A five-year-old oil palm plantation, planted on the Na Tham soil series (Fine loamy, mixed, isohyperthermic Oxic Plinthudults) with spacing 9x9x9 m, was selected for study. A randomized complete block design with three replications with 20 palms/replication was used. The treatments included six different rates
of fertilizer application. The rates of fertilizer were as follows: T1 (farmer practice), T2 (40% of application
rate in T4), T3 (70% of application rate in T4), T4 (urea 2,750 g/plant; triple super phosphate 1,500 g/plant;
potassium chloride 4,000 g/plant; kieserite 1,000 g/plant; borate 80 g/plant), T5 (130% of application rate in
T4) and T6 (170% of application rate in T4). The high leaf nutrient contents of N, P and K at the range of
2.6-2.8%, 0.16-0.18% and 1.13-1.18%, respectively, were found in the high nutrient application rate treatments (T5, T6). However, the amounts of leaf Ca and Mg in T5 and T6 decreased from 0.75-0.80% and 0.33-
0.37% at the beginning of experiment to 0.65-0.70% and 0.22-0.24%, respectively, at the end of the experiment. Small increases of leaf sulphur and boron up to about 0.20-0.22% and 16-19 mg/kg were also found
in the high rate of fertilizer treatments. Accumulated fresh fruit bunch yield (FFB) increased according to increasing rate of fertilizer application. Accumulated FFB yield of 268.4 kg/plant in the low fertilizer rate
(T1) (farmer practice) and 278.8 kg/plant in T2 were found compared with the highest yield of 370.2 kg/
plant in the highest fertilizer application treatment (T6) for the 3 years experiment. Regarding the economic
return, the medium rate of fertilizer application (T3) which achieved an accumulated FFB yield of 338.0 kg/
plant gave the highest profit with the VCR (Value: Cost ratio) of 2.53.