Surface properties of vertisols of Texas and Mexico under different land use systems

Due to increasing population pressures, there has been a worldwide report of soil degradation due to intensive land use or inadequate management practices. Vertisols (clay soils which exhibit shrink-swell activity) are an important soil resource in many countries and are among the soils that have experienced degradation. Understanding the dynamics of surface properties of Vertisols as impacted by various land use systems is important if remediation strategies are to be implemented.; The objectives of this study were to evaluate differences in morphological, chemical, physical, and porosity characteristics of (1) Vertisols as affected by different periods of controlled traffic no-tillage management (CT-NT); (2) Vertisols under different land use systems; and (3) Vertisols after long-term continuous cultivation of maize. The Vertisols were sampled in Texas and Mexico in a factorial sampling scheme to provide statistical comparisons between management or land use. Thin section samples were collected in 8 x 16 x 4 cm Kubiena tins from each site. These samples were impregnated with a polyester resin containing a UV fluorescent dye. Porosity attributes were determined by image analysis from polished blocks.; Once a native site undergoes cultivation, drastic changes occur in terms of morphological, chemical, biological, physical, and porosity characteristics. These changes are believed to be hysteretic in nature with a minimum of 6 years to exhibit pedality and porosity improvements. The rate and level of recovery under fallow or improved pasture conditions is largely determined on antecedent cultivation practices. Re-establishment of macrofauna provide the best opportunity for pedality and porosity recovery in Vertisols; even more significant that the self-mulching attributes of Vertisols. Thus, management plays an important role in restoration.; This study has revealed that porosity remains a complex and variable characteristic to evaluate. It is the subtle differences in pore geometry that show the effects of degradation and are indicators of rejuvenation. It is anticipated that other parameters such as pore shape factors or fractal geometry analysis will prove to hold significant implications in future analyses.