Long-Term Dryland Cropping Systems and Their Impact On Selected Soil Parameters in the Texas High Plains.

Due to the decline of the Ogallala aquifer and increasing dryland crop production in the semi-arid Texas High Plains (THP), efforts are needed to enhance soil quality and functioning, and particularly water holding capacity of dryland soils. The predominant cropping system in the THP involves continuous cotton, characterized by limited residue production and long fallow periods leaving the soil surface exposed most of the year. Dryland producers need alternative cropping practices that would improve the soil’s ability to capture rainfall, and thus, maintain adequate crop yields. Studies in humid regions have shown that crop rotations can increase soil quality, and that enhancements in organic matter (OM) can be associated with increases in soil water holding capacity; however, these improvements are more difficult to achieve in low OM soils characteristic of arid and semi-arid climates. In 2003, a dryland study was implemented to examine the effects of tillage and crop rotations on soil quality using selected chemical (soil pH, total C and N, and nutrient contents), physical (bulk density, aggregate stability, and water infiltration) and microbial (microbial biomass and composition, and enzyme activities) parameters. Despite occasional negative consequences of drought on the intended management practices and treatments, soil quality and functioning parameters in rotations with a winter cover crop showed positive impacts sooner than expected.  Rotations with winter cover crops (Hay-Rye and Cotton-Rye-Sorghum) provided higher plant biomass return and diversity of root exudates in soil, thus, increasing enzyme activities of nutrient cycling compared to Sorghum-Cotton after only 3 yrs.