Resumo

TORRES, Duilio; FLORENTINO, Adriana  e  LOPEZ, Marisol. Pérdidas de suelo y nitrógeno por escorrentía en un ULTISOL degradado bajo diferentes condiciones de cobertura vegetal en Chaguaramas-Guárico. Agronomía Trop. [online]. 2005, vol.55, n.4, pp.475-496. ISSN 0002-192X.

Conservation management practices were applied to an Ultisol with degraded physical, chemical and biological properties in order to recover  493 these properties and improve soil quality, emphasizing the reduction of soil and nutrient losses in runoff. These practices involved the application of a minimum tillage system combined with organic and inorganic fertilizers. Organic treatments were Sorghum bicolor L. Moench (gramineous residue, RG), Crotalaria juncea (leguminous residue, RL) and without residue (SR). Inorganic treatments were fertilizers Riecito phosphoric rock (RFR) and diammonium phosphate (FDA). After four years of application of these practices, an evaluation of their effect on soil and nitrogen losses in runoff was performed with simulated rain at an intensity of 120 mm/hour using a drip type rain simulator. Sediments were measured, dried and analyzed by the continuous flow colorimetric method to determine sediment associated nitrogen loss. A similar procedure was done with runoff water. Results obtained after four years indicate that soil and nitrogen loss parameters responded to management treatments. Lower soil and nitrogen losses were associated with higher degrees of plant coverage in combination with phosphoric rock. Soil and nitrogen losses were, respectively, 10,42 Mg* ha-1*year-1 and 9,2 Mg* ha-1*year-1 for RG+RFR and 4,2 Mg* ha-1*year-1 and 3,5 Mg* ha-1*year-1 for RL+RFR. The greatest soil (15,40 Mg* ha-1*year-1) and nitrogen (6,1 Mg* ha-1*year-1) losses, as well as runoff, occurred with SR+FDA, where coverage percentage was lowest.

Palavras-chave : Soil quality; indicators; crop residue; nitrogen losses; conservation practices.

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