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

Abstract

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.

Investigation of the Allelopathic Effect of Two Invasive Plant Species in Rhizotron System

“…When applied in higher concentrations, the ground materials clearly exhibit their negative allelopathic effect. This is supported by the study of Bodor et al [53], in which they demonstrated that powder made from pomegranate peel had a beneficial effect on the model plant when applied in the soil, resulting in the growth of its above-ground parts. This theory is supported by the results of Kazinczi et al [67], who investigated the allelopathy of several invasive plant species in potted experiments under greenhouse conditions and found stimulating effects in some species, which facilitated the development of cultivated plants, which indicates, on the one hand, the buffering capacity of the soil, and, on the other hand, that each species has a different allelopathic effect.…”

“…The use of soil-filled rhizotrons can be a good compromise between in vitro systems and field studies, allowing real-time, non-invasive studies of root system development [48]. Root responses of agricultural crops to different stressors have been investigated in such systems in several cases, e.g., treated with zinc [49] or nickel [50], combined heavy metal treatment modeling wastewater [51], polypropylene surgical mask fragments [52], or raw and nutrient-enriched pomegranate peel powder [53].…”