Efeito do uso da terra na disponibilidade de fósforo em solos do nordeste brasileiro

Abstract

Phosphorus (P) is naturally present in soils, but can be added through anthropic actions. Land use contributes to the accumulation and saturation of phosphorus in the soil, increasing the risk of P transport to aquatic bodies, accelerating eutrophication. The objective of this study is to evaluate the availability of P in the soil under different land uses and its relationship with physical and chemical attributes. A total of 28 sample plots distributed among different land uses (agriculture, cattle ranching and urbanization in riparian zones; and dumps and mines located outside the drainage basin) were evaluated for available P, clay content, exchangeable calcium, potential acidity and organic matter. For data analysis, descriptive statistics, Pearson correlation, Principal Component Analysis (PCA), and two-way cluster analysis of the soil attribute data were performed. The landfill and cattle ranching soils showed higher phosphorus availability among land uses. Agriculture showed to be the activity with the least impact on P availability in the soils, resembling natural soils with preserved native vegetation. Available P was positively correlated to organic matter content. Our results indicate that the increase in organic matter content and exchangeable Ca2+, and the reduction of the clay fraction may suggest an increase in phosphorus availability depending on land use. These results are important for planning and monitoring phosphorus in watersheds, avoiding the risk of eutrophication of water bodies.