Composting Onion (<i>Allium cepa</i>) Wastes with Alfalfa (<i>Medicago sativa</i> L.) and Cattle Manure Assessment

Abstract

There is growing interest in the potential for using composts in agricultural and horticultural field crops. The aim of this study is to test the mixture efficiency to produce good quality compost. This paper presents a comprehensive analysis of recycling organic wastes through composting. In an area of approximately 1500 ha, situated in the lower valley of the Rio Negro (Black River), onions are produced. 50% of these onions are processed under Good Agricultural Practices (GAP) and under Good Manufacturing Practices (GMP). The packaging for marketing in processing plants has produced huge volumes of wastes that must be managed according to quality standards. These are composed by scales, roots and leaves, with high C/N ratio. In this study the composting process was studied as a way to recycle ecological and cheap onion waste in order to minimize their environmental impact. The onion residues were mixed with alfalfa and cattle manure. An experiment was carried out in order to determine suitable quality compost (organic product high agronomic value). In order to achieve the objectives, composting processes were carried out in two consecutive years. During the process, some physical, chemical and biological properties of the final product were analyzed and evaluated. The mixtures: OMA, onion-manure-alfalfa; OM, onion-manure; OA, onion-alfalfa, showed a similar behavior. The mixtures more efficient were onion-manure and onion-manure-alfalfa with values close to 50%, while onion-alfalfa yielded only 34%. Reuse of onion waste by composting mixed with cattle manure, is a viable alternative in ecological terms. The final compost obtained could be used as amendment in agriculture practices.