Fertilization Effectiveness on the Productivity of Fresh Fruit Bunches and Maintenance Costs of Oil Palm Wandha Atmaka Aji, Aditya Dyah Utami, Bagus Nugroho, Toyyibah Toyyibah, Mukti Ahmad Nurcahya Buletin Penelitian Sosial Ekonomi Pertanian Fakultas Pertanian Universitas Haluoleo Vol. 22 No. 2 2021 DOI 10.37149/bpsosek.v22i2.13874