., Sudradjat, Hidayat Saputra, and Sudirman Yahya. 2015. “Optimization of NPK Compound Fertilizer Package Rate on One Year Old Oil Palm (Elaeis Guineensis, Jacq) Trees”. International Journal of Sciences: Basic and Applied Research (IJSBAR) 20 (1):365-72. https://gssrr.org/index.php/JournalOfBasicAndApplied/article/view/3417.