[Utilization of organic residues in alternative agriculture: determination of exogen nitrogen requirements of maize]
1994
Garcia M, Jimena Rosa
Studies on organic residues and its agricultural utilization are becoming of primordial importance as a tool for development strategies effectively accessible by small farmers. The objective of this work, is to evaluate the behaviour of two stabilized organic residues, compost and biofertilizer and their combinations with urea, as enhancers of some physical and chemical characteristics of soil and as organic in maize. The essay was carried out at the "Canelo de Nos" center, and it comprised 12 treatments with compost, 10 and 30 ton/ha, two treatments with urea, 90 and 180 kg N/ha; four treatments that combine organic fertilizer with urea, at different doses of the last; a control treatment, and a control with phosphorus. In the combinations of organic fertilizer and urea, the dose of urea is determinative on the mineralization dynamics of the nitrogen found in the organic fertilizers, when mixed with the soil. It has been considered that the lower urea dose, produces at a first phase a immobilization of nitrogen by microbial populations, that grow till they reach a new equilibrium, causing a lower crop production, due to a lesser nitrogen availability at certain stages of development. Organic fertilizers incorporation to soils at a dose of 30 ton/ha, specially compost, produces yields similar to those of the high urea doses. However, at the 10 ton/ha organic fertilizer dose, yields are lower than these of the controls without fertilizer. No effect of organic fertilizers on soil physical and chemical properties was observed. This supports references that point out that changes can be noted only after several years of organic fertilizations with big amounts
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