| The processes of soil degradation due to conventional rain-fed agricultural practices, and natural rehabilitation during abandonment period (fallow) were examined in vertisols from a representative semiarid area of Northeastern Mexico. One agricultural chronosequence of sites with 3 to 30 years of land use was selected, while the fallow chronosequence included sites with 2 to 22 years of abandonment. More than 50% of soil organic carbon and total nitrogen were lost after 30 years of cultivation, with initial sharp reductions followed by equilibrium after six years. Increases in soil alkalinity and bulk density, combined with a reduction in soil macroaggregates were also observed. Soils recovered 34% of soil organic carbon and 62% of total nitrogen during the fallow as well as an improvement in soil aggregation. Significant correlations were observed between soil organic matter and total nitrogen and pH, but the influence of soil organic matter on soil physical properties was not clear. Further research is needed to determine the precise influence of soil organic matter in soil physical properties of vertisols. |
