Vermicomposting of biomass ash with bio-waste for solubilizing nutrients and its effect on nitrogen fixation in common beans

In the last two decades, biomass incineration plants have been widely used to manage bio-waste, crop and forest residues that produce recalcitrant nutrient-rich biomass ash (BA), but have limited their use for agricultural purposes. Considering the urgent needs for a sustainable agro-industrial waste management, the present study aimed to fulfill the scarcity of the literature in this field by focusing on one of the bioremediation strategies (vermicomposting) to solubilize the potential plant nutrients, specifically phosphorus of the BA for crop fertilization. BA was collected from the biomass power plant incinerating poultry litter, forest and crop harvest residues, and then thoroughly incorporated into dewatered dairy manure to obtain final NPK content of 0.0 (T-0), 3.5 (T-1), 7.0 (T-2), and 10.0% (T-3) on a dry weight basis. Initially, the mixtures were pre-composted aerobically for 3 weeks to remove toxic gases and then subjected to vermicomposting for 60 days. The sequential extraction results indicated that vermicomposting significantly improved solubility of total phosphorus (TP) and Olsen-P by 69%-79% and 5%-8%, respectively, depending on the BA doses. Pot experiments were conducted using common bean (Phaseolus vulgaris L.) in 0.0%, 3.5% BA, 7.0% BA and 10.0% BA vermicompost, respectively. The results indicated that BA vermicompost amendments could promote the growth of bean plants, increase the content of chlorophyll contents in the leaves, and significantly enhance the synthesis of leghemoglobin in nitrogen-fixing compartment of root nodules (p < 0.05), which helps the activation of the biological nitrogen fixation. Findings of this study clearly demonstrated that vermicomposting of BA with bio-waste could ameliorate the solubility of nutrients from BA, and nutrient-enriched vermicompost could improve the nodulation and nitrogen-fixing ability of legume crops, thereby enhancing its recycling capacity for closing nutrient loop. (C) 2021 Elsevier B.V. All rights reserved.