The amount of manure available on farms in the semiarid region of Northeastern Brazil is usually insufficient to fertilize the cultivated areas. Besides this, in most cases the manure available is of low quality and may immobilize soil nitrogen. For these reasons, the use of green manures, such as gliricidia prunings, or the mixture of these with animal manures, may be a good alternative to increase the availability and quality of organic fertilizers. The initial growth and uptake of nutrient by cotton and castor bean fertilized with manure and/or gliricidia were measured in two consecutive growing periods in the greenhouse. The treatments were: incorporation 20 t ha-1 of manure; incorporation of 20 t ha-1 of gliricidia prunings; incorporation of the mixture of 10 t ha-1 of manure and 10 t ha-1 of gliricidia; and a control without fertilization. The treatment with gliricídia incorporation resulted in better development of both crops, greater soil N availability, greater accumulation of nutrients in the dry biomass of the crops, and greater apparent recovery of N, P and K, relative to the other treatments. The manure did not increase soil N availability, but the mixture of manure and gliricidia increased availability of soil N, P and K in relation to the control treatment, proving to be a promising practice capable of improving the quality of animal manure.
Ricinus communis; Gossypium hirsutum; organic fertilization; green manure
