Abstract

Agroindustrial waste-derived amendments may be used as substitutes for synthetic fertilizers to improve soil physicochemical and biological properties and crop production. Microbial activity plays an essential role in the beneficial effects of organic amendments on soil quality. In this study, we investigated the combined effects of two different agroindustrially-derived amendments, namely, beef cattle manure (CM) and lemon peel (LP), on soil biological properties, plant nutrition and antioxidant responses in ryegrass to evaluate their putative use as organic phosphorus fertilizers. A combined amendment of CM + LP was more effective than each amendment used separately. For example, the microbial biomass in the CM + LP group was more than 4 times that of the control. This can be largely attributed to the fungal community because the richness biodiversity index was greater than that of the bacterial and fungal biomass. The bacterial biodiversity index of the treated soils was lower than that of the control but was less dominant and more changeable with soil chemical parameters such as Al content and pH. Interestingly, ryegrass yield and phosphorus uptake significantly increased with the addition of combined CM + LP (43% and 44%, respectively) with respect to treatments with synthetic supertriple phosphate fertilizer (STP). Less oxidative stress was observed in treatments with CM + LP supplementation than in treatments with supertriple phosphate fertilizer. In conclusion, the combined application of CM + LP showed a beneficial effect on P uptake and oxidative stress with a concomitant increase in plant productivity, indicating that the combined amendment could be used as an organic fertilizer to improve the soil fertility and sustainability of agricultural production systems.