Concentrações e estoques de fósforo em diferentes classes, usos e coberturas de solos no Agreste pernambucano

Abstract

Changes in land use cause a mosaic of areas in the landscape with different uses and land cover. This condition compromises the nutrients in the soil, being relevant for food production, mainly because they can compromise losses and reduction of phosphorus (P) stocks in the system. Therefore, this work aimed to determine the phosphorus concentrations in the depths of the main classes in different uses and soil cover in the Agreste region of Pernambuco. Samples from the soil bank collected by the group of researchers from the Department of Nuclear Energy of the Federal University of Pernambuco, carried out between 2011 and 2015 were used for these studies. Thus, extractable and total phosphorus concentrations were determined in (192 samples) in 04 classes (Algisol, Litholic Neosol, Regolithic Neosol and Planosol) of soil, 04 land uses (Open Caatinga, Dense Caatinga, Agriculture and Pasture) in 04 layers (0-10, 10-20, 20-30 and 30-40 cm). To determine the extractable P, the Mehlich 1 and colorimetric reading were used. The total phosphorus was determined by sulfuric digestion to obtain the extracts and also being determined by colorimetry. The results of the concentrations found for both extractable and total P were higher for the Argisol and Planosol classes. It was observed that there were reductions in extractable P concentrations between the soil layers as the soil profile deepened. The superficial layers, between 0-20 cm, generally presented the highest concentrations of extractable and total phosphorus in agriculture. Among the four soil classes studied, the highest average values of extractable and total P stocks occurred in Litholic Neosols and Planosols, mainly due to agricultural use. P is an element of great importance for plant development. P deficiency has been a limiting factor to agricultural productivity and, especially in the Agreste region of Pernambuco, where the main soil classes under natural cover have low levels of available and total P. Finally, the sustainable management of natural ecosystems and knowledge of the dynamics of P in the soil are extremely important to increase its bioavailability in tropical soils.