The Application of a Bio-Stabilized Municipal Solid Waste-Based Fertilizer for Buckwheat Production

In a circular economy framework, waste valorization in crop production promotes sustainability in the agricultural sector. Buckwheat (BW; <i>Fagopyrum esculentum</i> Moench) has promising nutritional and economic value. Its sustainable production can be promoted by applying organic fertilizers. Aimed at determining the effect of a bio-stabilized municipal solid waste (MSW) amendment on BW, a greenhouse experiment was performed combining two different soils (clay and sandy) with three previous fertilization treatments (no fertilizer, mineral fertilizer, or MSW fertilizer) from the precedent faba bean crop and three present fertilization treatments (no fertilizer, mineral fertilizer, or MSW fertilizer) from the precedent wheat crop. The present fertilizer treatments followed the same procedure and fertilization rates (7.9 g/kg clay soil and 6.7 g/kg sandy soil of MSW amendment and 0.14 g/kg clay soil and 0.12 g/sandy soil of mineral fertilizer) as the previously fertilized treatments to study the effects on BW crop and soil. Results indicated a positive response of biomass production (on average 34.4 g/plant) and seed yield (on average 10.6 g/plant) to direct organic fertilization, obtaining comparable results with respect to the mineral fertilization treatments. Additionally, organic fertilization significantly enhanced seed quality and nutrient content compared to mineral fertilization, which resulted in a higher chlorophyll content. The findings revealed that the residual effect from the previous bio-stabilized MSW amendment was not sufficient to provide the total nutrients necessary for BW potential growth and biomass production, although slight tendencies toward increase were observed. Soil properties, such as organic matter and nitrogen content, as well as soil nutrient concentrations, were positively affected by organic fertilization, presenting adequate levels of heavy metals (Cu, Zn, Pb, Ni, Cr, and Cd). The insights of this study are valuable to determine the effects of reusing waste by-products for BW crop fertilization to reduce or substitute for chemical fertilizers.