Plantas de cobertura e doses de torta de mamona no cultivo orgânico de alface sob plantio direto

Abstract

No-tillage system and organic agriculture has been bringing benefits to environment, agriculturist and consumer. However, there are still little information about the most adequate practices to no-tillage system, specially about vegetables production, and organic. The use of industrial residues is an interesting practice by the environmental and economic points of view. This is the situation of castor cake, which cultivation has been expanding due to biodiesel production. Lettuce (Lactuca sativa L.) is the most consumed leaf vegetable and, being this consume in natura, it has a high aggregated value when organically produced, without pesticides. The present work had for objective to study the effect of covering cultures and castor cake doses, compared to a mineral treatment, over the agronomic performance and postharvest quality of lettuce. The experiment was accomplished in the experimental field of the Agriculture Department of UFLA, Lavras, MG, Brazil, from September, 2008 to April, 2009. The experimental design consisted of a split-plot scheme in completely randomized blocks with four replications. The plots consisted of six covering plants: Crotalaria juncea L., Canavalia ensiformis (L.) DC, Cajanus cajan (L). Millsp, Pennisetum glaucum (L.) R. Brown, Mucuna aterrima (Piper & Tracy) Merr. and spontaneous vegetation. The subplots consisted of five fertilizations: mineral with 120 kg/ha of N and organic with 0, 60, 120 e 240 kg/ha de N. It was applied 100 kg/ha of P2O5 and 60 kg/ha of K2O on every treatments, by superfosfato simples and potassium clorate for the mineral, and termofosfato and ash for the organic. The covering plants were seeded on the plots, cut by 134 days and distributed over the soil. The plots were split in the five fertilizations. The lettuce seedlings were planted over the mulch, by 43 days after seedling. The harvest was made by 73 days after seedling.