@article{Purwanto_Sudradjat_Supijatno_2017, title={Determination of Nitrogen Fertilizer Requirement for Four-Year-Old Oil Palm}, volume={5}, url={https://www.ajouronline.com/index.php/AJAS/article/view/5097}, abstractNote={Fertilization is one of the methods to increase the productivity of oil palm in Indonesia, especially in smallholder plantations. The aim of this research were to study the effect of nitrogen (N) fertilizer and to determine the optimum N fertilizer rate for a four-year-old oil palm (1<sup>st</sup> mature oil palm). This study was conducted at IPB-Cargill Teaching Farm of Oil Palm, Jonggol, Bogor, Indonesia from April 2016 to March 2017. This experiment used one factor of randomized complete block design that consisted of five treatment levels, three replications and five palm samples. The treatment levels were 0, 725, 1450, 2175 and 2900 g N palm<sup>-1</sup> year<sup>-1</sup>. Nitrogen fertilizer significantly affects the palm height, trunk girth, leaf area, leaf greenness, stomata density, leaf N content, bunch number, and productivity of fresh fruit bunches (FFB), but didn’t affect the frond length and average bunch weight on 1<sup>st</sup> mature oil palm. The optimum N fertilizer rate was 1632 ± 207 g N palm<sup>-1</sup> year<sup>-1</sup> for four-year-old oil palm (1<sup>st</sup> mature oil palm). Application of N fertilizer with application rate of 1632 g N palm<sup>-1</sup> year<sup>-1</sup> could increase the productivity by 35% compared to control (4.9 ton FFB ha<sup>-1</sup> year<sup>-1</sup> higher than control).}, number={6}, journal={Asian Journal of Applied Sciences}, author={Purwanto, Oky Dwi and Sudradjat, Sudradjat and Supijatno, Supijatno}, year={2017}, month={Dec.} }