Soil fertility plays pivotal role in adopting intensive agricultural approaches which are becoming popular and essential to feed the ever-increasing population with limited available resources. The use of organic fertilizers offers a sustainable approach by improving soil fertility and reducing dependence on chemical fertilizers. We investigated the production level of frass, an organic fertilizer, by Black Soldier Fly (BSF) when fed with animal and plant-based substrates.While being commercial, plant-based compost fertilizer was used as a standard positive control and was labelled as CPC.Plant based wastes reduce the decomposition rate for Organic Nitrogen (ON) and ON-NH₄⁺ when used as a feeding substrate for black soldier fly larvae (BSFL). On the other hand, it enhances the decomposition rate for total crude fibre (TCF), NH₄⁺-NO₃^- and NO₃^- uptake rate. Contrary to this, we observed highest decomposition rate for ON and ON-NH₄⁺ and lowest decomposition rate for TCF and NH₄⁺-NO₃^- along lowest NO₃^- uptake rate by BSFL using animal-based wastes as feeding substrate. Frass produced by black soldier fly when fed with plant-based substrate (BSFFP) recorded a balanced uptake ratio for NH₄⁺:NO₃^- (33:37), whereas Black soldier fly frass based on animal-feeding (BSFFA) recorded unbalanced uptake ratio for NH₄⁺:NO₃^- (40:08). Commercial plant-based compost fertilizer (CPC) used as the positive control, recorded higher NH₄⁺ uptake (25) compared to NO₃^- uptake (17). Furthermore, the use of CPC showed the lowest rate of ON-NH₄⁺ (0.36 ± 0.002) as well as lower NH₄⁺-NO₃^- rate (0.60 ± 0.003) compared to BSFFP. This study highlighted the importance of both ON form and TCF decomposition rates as key determinants for effective nitrification (NH₄⁺-NO₃^-) and NO₃^- uptake of BSFF frass-based fertilizer.