Yoanma, A.D. et al. 2022. Effect of Coconut Shell Biochar Application on the Effectivity of NPK Fertilizer in Red Onion (Allium ascalonicum L.) Cultivation. Jurnal Teknik Pertanian Lampung (Journal of Agricultural Engineering). 11, 1 (Mar. 2022), 1–14. DOI:https://doi.org/10.23960/jtep-l.v11i1.1-14.