The objective of this study was to evaluate the effects of application of six years of organic manure with animal and/or cover crop on the fertility of an Entisol. Treatments were: 1) animal manure (15 t ha-1); 2) use of Crotalaria juncea L. as a cover crop; 3) fertilization with half (7.5 t ha-1) of the usual doses of animal manure combined with C. juncea L. as a cover crop; and 4) control plots without application. The study was conducted from 1996 to 2003, but no fertilization was done in 1998 and 1999, due to severe droughts. At the end of 2003, soil samples from two depths (0-20 and 20-40 cm) were collected and analyzed to determine the nutrient concentrations. The annual fertilization with animal manure, with or without C. juncea, increased soil extractable P, K, Mg and B in both soil layers, but increased soil organic carbon, total N, total P, and Zn only in the 0-20 cm layer. The cultivation and incorporation of C. juncea had no consistent effect on soil fertility. The results have shown that the application of lower doses of manure combined with C. juncea maintained soil fertility at levels comparable to application of 15 t ha-1 of animal manure.
manure; Crotalaria juncea L.; green manure; semi-arid region of NE Brazil; micronutrients
