Fitra Syawa Harahap, I. . Arman, N. . Harahap, F. . Ahmad Syawaluddin, and R. . Fitra Yana, “Provision of Chicken Manure and Urea Fertilizer on the Chemical Characteristics of Ultisol Soil in Bilah Barat District”, IJSE, vol. 2, no. 3, pp. 98–103, Aug. 2022.