Teores de nutrientes e estoques de carbono orgânico em neossolo litólico sob diferentes coberturas vegetais em região semiárida.

Abstract

Changing caatinga soil cover for pasture without proper management causes soil degradation due to nutrient and organic matter loss, but little is known about the impact of this change. Inadequate management by replacing pasture land cover can lead to significant nutrient and organic matter loss in soil, changing its dynamics and consequently changing nutrient inputs and outputs in the system, thus causing soil degradation. In this work the objective was to evaluate the nutrient content and the organic carbon stock in Litolic Oxisol under caatinga and degraded pasture in Paraiban semiarid. The research was developed at the experimental station Prof. Ignacio Salcedo belonging to the National Institute of Semiarid (INSA), located in the municipality of Campina Grande, Paraíba, Brazil. The climate of the region is semi-arid and the soil of both areas classified as Neolithic. The areas were characterized as a preserved caatinga area and the other area as a degraded pasture. Soil samples were randomly determined at fifteen sampling points at a distance of 20 meters, up to 40 cm deep at 10 cm intervals, totaling 120 samples. The soil samples were then air dried and sieved with a 2.00 mm mesh to determine the available P, K +, Ca2 + and Mg2 + exchangeable concentrations and pH. Sub samples were ground in mortar to determine organic carbon concentrations. Data were subjected to analysis of variance at 5% level. The available P concentration in the caatinga was significantly higher than in the degraded pasture in the 0-10, 10-20 and 20-30cm soil layers. Ca + and Ca2 + concentrations were higher in the 0-10 and 10-20 cm layers and Mg2 + only in the 20-30 cm layer. The concentration of organic carbon at each depth was significantly affected by vegetation cover, always with the highest values for caatinga, which also provided higher carbon stock (65.26 Mg ha-1) for this area. The concentration of organic carbon is higher in soil under caatinga than under degraded pasture to a depth of 0-40 cm, at this same depth the carbon stock is also 34% greater than degraded pasture.