N. A. Tampubolon, Z. Muktamar, and M. F. Barchia, “The Effect of Eco Enzyme from Pineapple (Ananas comosus) Peel Waste on Soil pH, P Availability, Growth and Yield of Shallots (Allium cepa) in Ultisols ”, TERRA, vol. 6, no. 2, pp. 51–56, Dec. 2023.