Phytotoxicity evaluation of nutrient-fortified pomegranate peel powders prepared from food waste and their feasibility as biofertilizers

Pomegranate peel powder (PPP) is increasingly used as a bioadsorbent to decontaminate wastewaters due to its adsorptive characteristics. The application of nutrient-fortified bioadsorbents as alternatives to chemical fertilizers can provide an innovative and eco-friendly approach for sustainable waste management. Nevertheless, there is extremely limited information regarding their effects on the growth of agricultural crops. We investigated the effects of raw and nutrient-fortified PPPs on oilseed rape (Brassica napus). Our results showed that the concentration-dependent in vitro phytotoxicity of high PPP doses (germination indices were 109.6%, 63.9%, and 8.9% at the applied concentrations of 0.05%, 0.5%, and 5%) was diminished by the application of nutrient-fortified PPPs (germination indices were 66.0-83.4% even at the highest doses). In pot experiments, most PPP treatments (especially Raw-PPP and the mixture of N- and P-fortified PPPs) promoted the development of aboveground plant parts. Reorganization of the pattern of protein tyrosine nitration in the root tissues indicated that the plants were acclimated to the presence of PPPs, and thus, PPP treatment induced no or low-level stress. Our findings confirmed that several doses of PPP supplementation were beneficial for the model crop plant when applied in soil. We anticipate that our study will be a foundation for future investigations involving more plant species and soil types, which can contribute to the introduction of nutrient-fortified PPPs as sustainable biofertilizers.

Automated summary

Pomegranate peel powder (PPP) is used as a bioadsorbent to decontaminate wastewaters. Nutrient-fortified PPPs can reduce the phytotoxicity of high PPP doses and promote plant growth. Our findings provide a foundation for the use of nutrient-fortified PPPs as sustainable biofertilizers.