USO DE TORTA DE MAMONA COMO FONTE DE NITROGêNIO NA PRODUTIVIDADE DE CULTIVARES DE CEBOLA SOB CULTIVO ORG?NICO NO VALE DO S?O FRANCISCO

摘要

With the objective of evaluated the yield of onion cultivars under organic crop system nitrogen, using the castor bean caker with nitrogen source in the conditions of the S?o Francisco Valley, an experiment was conducted in the period from January to September 2008 in Petrolina - PE. The experimental design was randomized complete blocks in a 4 x 2 factorial scheme, understanding four nitrogen levels (0, 70, 100 and 130 kg ha-1), using the castor bean caker as a source (5% N) and two onion cultivars ( Brisa IPA -12 and Franciscana IPA -10), with four replications. The commercial yield of bulb showed a linear effect with the increase of the applied doses of nitrogen for the Brisa IPA-12 and Franciscana IPA-10 cultivars. Regarding non-commercial yield (culls) a negative lineal effect it was showed with the increment of the doses, being observed with the increase of the doses of N reduction in the production of bulbs of smaller size. The fresh mass commercial bulb and the percentage of bulbs larger diameter increased linearly as increasing the nitrogen levels in both cultivars.