Changes in soil chemical properties under different farming systems exploration in semiarid region of Paraba

The change of Caatinga natural vegetation in the Brazilian semiarid region, to different systems of agricultural exploitation, that is, the replacement of complex and stable systems by simple and unstable systems has caused changes in soil properties that are dependent on the climate, the type of crops and the management adopted. Based on areas of Caatinga native vegetation, this study aimed to evaluate the changes in the chemical characteristics of soils under different farming systems in Paraiba backwoods. Vertissol samples were collected at 0 to 10, 10 to 20, 20 to 30 and 30 to 40 cm and chemically characterized. Selected systems were native vegetation, sparse vegetation, pasture, annual and permanent crops. Based on the statistical analysis, it was concluded that the replacement of native vegetation by agricultural farming systems in the region of watershed Riacho Val Paraiso, PB, caused changes only in pH, potassium and sodium in the soil attributes. There was a trend of soil chemical properties increasing in the areas of agricultural cultivation and with depth. In all areas of agricultural farming systems, soil fertility is suitable for most crops.   Key words: macronutrients, land use, soil depth.