Soil fertility changes in vineyards of a semiarid region in Brazil

Cultivation can substantially change soil quality through improvement or degradation of the physical and chemical characteristics. Vineyard soils are sensitive to soil changes due to the intensive chemical input. This study assesses the soil fertility changes in vineyard soils of the Sao Francisco valley in Northeastern Brazil during different cultivation time spans (5, 6, 8, 10, 12, 15, and 16 years). An area with natural vegetation (Caatinga) was used as a reference area. We analyzed pH, exchangeable contents of Ca, Mg, Na, K, and Al, potential acidity (H+Al), available P, total organic matter, sum of bases, CEC, Al saturation, and base saturation at depths of 0-20 and 20-40 cm. Univariate and multivariate analyses were used for data evaluation. The results showed that soil fertility changes were closely related to cultivation time spans. Contents of organic matter, Ca, Mg, and K were increased in most of the vineyard soils. The management of P fertilization deserves attention as the very high concentrations in soil are prone to leach and can contribute to triggering eutrophication. Discriminant and factor analyses proved to be useful tools for distinguishing the effects of management in the cultivated areas and helping to achieve sustainable land use in such fragile agro-ecosystems.