LAUSR

Abstract We assessed long-term cultivation effects on several structural stability indicators within the 0- to 5- and 10- to 15-cm depth increments of different Oxisols. Comparisons were made between native and cultivated soils managed using no-till (NT) practices for 12+ years. Overall, conversion significantly decreased structure stability due to machinery traffic, high fertilizer and lime applications, soil organic matter (SOM) depletion, and reduced input of organic material (roots and crop residues). The magnitude of change varied depending on inherent (mineralogy) and dynamic (cropping system) factors, as well as soil depth. Kaolinitic Oxisols were much more susceptible to degradation than Gibbsitic Oxisols. Combining more diversified cropping systems with NT can mitigate the negative effects of cultivation by increasing living vegetation and crop residue additions throughout the entire year. Increased quantity and quality of SOM input improves soil biological activity and improves topsoil structural stability. Those changes also reduce eluviation of dispersed clay (primarily kaolinite) with percolating water and prevent concentration of the clay at the 10 to 15 cm depth, which further degrades the soil by contributing to formation of the dense subsurface layers beneath either NT or conventional production systems.