Effects of the onion residue compost as an organic fertilizer in a vegetable culture in the Lower Valley of the Rio Negro

Purpose Farming production in the lower part of Rio 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, 60 and 80 Mg ha-1) 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 weight. 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.