FERTILIDADE DE DIFERENTES CLASSES DE SOLOS SOB UM GRADIENTE CLIMÁTICO DA REGIÃO SEMIÁRIDA

Abstract

Soil chemical and fertility properties provide subsidies for the development of appropriate land use, management and conservation practices. The objective of this study was to determine the chemical and fertility attributes of nine soils, representing three classes of soils frequently found in the semiarid region of Paraiba state. along a rainfall gradient. In this region soil formation is hampered by low levels of rainfall, resulting in younger or poorly developed soils that retain many characteristics of the parent material. Thus, we selected Regolithic Neosols, Luvisols Haplic and Planosols Nátricos, going from very dry, dry and wet areas in the state of Paraiba. We opened nine trenches, identified and sampled each horizon, retrieving a total of 41 soil samples for chemical characterization (P, K, Ca, Mg, Na; Al, H + Al; pH; BS; CTCef; CTA7;% V; m%), and particle size. Weighted averages based on horizon thicknesses were used to obtain attribute values for the 0-20 cm layer. The sand fraction was predominant in the three soil classes, while the clay fraction showed the lower levels, regardless of soil class and rainfall condition. Overall, the three soil classes showed low fertility, but there was an increase in soil fertility with increasing rainfall, except for the Luvisol. Expected relationships between pH vs. V% and pH vs. (H+Al) confirmed the consistency of the overall soil fertility data for the 0-20 cm layer, since they included all soil-rainfall combinations.