Calcareous soils in the Northeastern of Brazil: Alterations of attributes from different land use history

The intensive machinery traffic is an important feature of industrial agroecosystems. This traffic when performed under inappropriate moisture conditions can accelerate a series of soil physical properties exchanges, causing deterioration of several soil quality indicators. Intensive agricultural activity is advancing rapidly in western Sergipe State and northeastern Bahia State (Brazilian semi-arid regions), mainly on soils developed from limestone substrata. This study characterized the soils and investigated the effect of increasing periods of corn crops and other land use types on soil attributes of calcareous soils from Western Sergipe State, with emphasis on physical attributes, particulate organic matter, and total organic C. Five combinations with five replicates of land use were selected: dry forest (DF); corn crop (first, fourth and tenth year - C1, C4 and C10) after forest removal; and intensive pasture (IP). The study areas were dominated by soils with vertic properties. Almost all the chemical and physical attributes showed a lesser quality in IP sites compared with the other treatments. The differences among the DF sites and corn crop sites were smaller. When compared the land use time of corn crop treatments (with DF as zero time), tenuously, some attributes formed two groups, where DF and C1 treatments were separated from C4 and C10 treatments. Regarding the comparison of all treatments, the non-metric multidimensional scaling technique explained 94% of the variability (in two axis) of the 19 attributes analyzed, being the major part represented by axis 1 (79%). The IP sites had the greatest soil physical degradation index among all groups. The C1 sites had significant contrast compared with the DF sites. The C4 sites showed a loss of quality in many soil physical properties compared with C1 sites. There were no differences between the C4 and C10 sites. This shows that in order to achieve a near steady state a greater number of cultivation years is required.