Abstract

BORGES, Jorge A et al. Physical and chemical characteristics of soil and their association with nutrients in areas for grazing in Yaracuy State. Bioagro [online]. 2012, vol.24, n.2, pp.121-126. ISSN 1316-3361.

The objective of this work was to study the association between phosphorus, calcium and potassium, and physicochemical parameters such as texture, relief, organic matter (OM), pH, and electrical conductivity in soils with pastures in dual purpose production units in Yaracuy State. Soil samples were taken in production units of the municipalities Manuel Monge, Veroes, Bolivar and Nirgua, during the dry period (December 2009-February 2010), at depths of 0-20 cm, which were processed by routine methods of soil fertility analysis. The data were sorted by texture and relief and compared by analysis of variance (Anova) and mean separation by Tukey for chemical variables (OM, pH and EC), as well as regression and correlation analysis of the elements (P, K and Ca) as a function of physical and chemical variables. It was found that soils were lacking phosphorus (<10 mg·kg^-1) and calcium (<500 mg·kg^-1) mainly in Bolivar municipality (83.3 %) and in soils sandy texture (31.0 %) and flat relief. Average concentrations of potassium (±125 mg·kg^-1) were in all cases above the critical value. The contents of organic matter were significantly different among soil textures and relief, being higher in middle-fine soils and in mountainous areas (4.82 and 5.36 % OM, respectively). The pH was shown to be strongly associated with the nutrient availability, particularly calcium (R²=0.79), in which the deficiencies were found in acid soils and corresponded to 58.6 % of the soils studied (±288 mg·kg^-1). We conclude that the characteristics of relief and pH act as predisposing factors in the availability of some minerals and organic matter, and phosphorus proved to be the main deficient element in these soils devoted to herding cattle.

Keywords : Soil analysis; mineral nutrients; organic matter; cattle herds.