Purpose Farming production in the lower part of Río Negro Valley (Argentina) has increased considerably during recent years, causing soil degradation and, specifically, decreasing the organic matter contents. This fact requires recovery measures, as organic amendments for soils, to improve its quality. The marked objectives for the present research is to evaluate compost as organic fertilizer, based on a mix of onion waste and bovine manure. Methods The experiment was carried out in a completely randomized design, involving five treatments and one control, with ten copies of each one. Tests were performed in a greenhouse, using flowerpots and experimental plots, in a typical soil of the region (Aridisol), pH 8.3 and 2.2% of organic matter, mixed with different compost dosages (20, 40, ) and the chemical treatment, Urea (0.26 Mg ha -1 ). A horticultural farming of 1 lettuce was sowed (Lactuca sativa). A conventional handling was carried out for the whole cultivation period, and at the end was harvested. Ten plants per plot were taken and were determined total fresh weight, aerial part fresh weight, root part fresh eight. In the dry controls total dry weight, aerial dry weight and root dry weight was determined. Results Results show, with an error (p \ 0.05), significant differences in the fresh weight per plant calculated, between treatments and control; a noticeably greater effect can be observed in the treatments with 6 and 8 kg m -2 compost amending and urea treatment. There is no evidence of the existence of significant differences (p \ 0.05) between treatments and control, according to the values obtained for root size as well as aerial dry weight and root dry matter. Conclusions It can be concluded that the addition of organic fertilizer to soils, has positive effect on the Fresh weight of the plant, recommending the use of doses of 6 kg m -2 while the dose of 8 kg m -2 could replace the use of chemical fertilizers such as Urea.

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From the results of the present study, it can be inferred that the irrigation method does have an influence on the incidence of diseases of bacterial origin in the post-harvest stage for onions. © 2018 Society of Chemical Industry.

The production of onion waste derived mainly from bulbs affected by fungal diseases, during onion classification and storage presents an important agro-environmental issue in onion production regions. Composting is an environmentally friendly strategy to recycle agricultural waste and produce organic fertilizers. Modifications of the microbial community in soil can affect the ability of pathogen propagules to survive, germinate and infect plant roots. Hence, the main objective of this work was to exploring the mechanisms involved on the presence of three soil-borne phytopathogenic fungi during the composting process of onion waste under the hypothesis if that the resulting compost effectively prevents or minimizes the dispersion of phytopathogenic fungi. To this end, three composting piles of 60 tonnes each were built by layering onion waste affected by phytopathogenic fungi and cow dung at 1:1 ratio. Temperature, moisture, pH, electrical conductivity (EC) and Aspergillus niger, Penicillium sp. and Fusarium sp. growth were monitored for 100 days. During the first 28 days of composting, the presence of phytopathogenic fungi increased significantly showing thereafter a downward trend. Final estimations of fungal populations densities indicated a predominance of A. niger and an effective reduction in the abundance of Fusarium sp. This pilot-scale work demonstrates the feasibility of composting onion waste contaminated with phytopathogenic fungi and highlights the positive environmental impact associated with this practice. Therefore, the composting of onion waste and cow dung is a feasible and sustainable procedure to recycle onion waste and to promote circular economy in onion production regions.

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Concentrations of soluble carbohydrates were analysed during storage in three onion cultivars (Allium cepa L.): Valcatorce INTA, Grano Oro (both with brown skin) and Antartica INTA (with white skin). These cultivars are produced in the Low Valley Negro River, to internal and external market. Carbohydrates were assessed by Gas Chromatography with Flame Ionization Detector (GC-FID), based in methanol-water extraction 80%. The ANOVA revealed highly significant difference (P<0.001) between cultivars and glucose, fructose, and total carbohydrates. Total sugar compositions throughout storage have scarcely increased after eight weeks and varied within cultivars (P < 0.05). The ratio monosaccharide to disaccharide had a significant cultivar effect (P < 0.001), and over twelve weeks of storage was monosaccharide domineering. Valcatorce INTA had the higest ratio (17.5-13.2); Grano Oro intermediate (12.1-10.9), and Antartica INTA the lowest (4.7-3.5). There was a peak of sucrose level that would be announcing the onset of sprouting four weeks post harvest, which was significantly different for Valcatorce and Antártica (Tukey test P<0.05), and was not significantly different for Grano Oro. These results are evidence of quantitative differences of sugars, due mainly to genetic factors. The implications of quality and storability are discussed.

Using different agricultural waste composts as organic amendments or substrates for seedlings has increased in recent years. From remote times, organic waste has been associated with disease and agriculture fertility. However, determining the load of phytopathogenic microorganisms that can persist in mature compost is essential given the risk of them becoming a transmitter of disease. In the present work, A. niger survival in mature compost made with onion waste mixed with cattle manure and alfalfa waste was assessed. The relationships between the inoculum of A. niger loads present in mature compost and the quantitative ranges of the evaluated parameters were established. To this end, the Aspergillus niger inoculum in the onion compost, obtained after a 6month composting process, was used. The pH, EC and C:N ratio values in the three compost products do not limit them from being used as substrates in horticultural seedling production or as an organic soil amendment. These results are consistent with the research reported by other authors. Hence this compost can be successfully used as a substrate component in horticultural seedling production and as an organic fertilizer in soils without damaging crops.

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.