In the Texas Rolling Plains, low rainfall results in low crop residue production and low soil organic matter. Low soil organic matter, coupled with low levels of silt and clay, give soils poor structure. An 11-year (1979-1989) field experiment was conducted to determine the effects of tillage (reduced vs. conventional), cropping, and residue management (with residue vs. without residue) on soil properties under dryland and irrigated systems. Cropping included a grain sorghum (Sorghum bicolor (L.) Moench.) and wheat (Triticum aestivum L.) monoculture and doublecropped, reduced tillage wheat-grain sorghum under irrigation only. Surface soil organic matter in plots with irrigated grain sorghum and wheat increased with time. Reduced-tillage irrigated grain sorghum and wheat, and especially reduced-tillage, double-cropped grain sorghum and wheat plots, had significantly higher organic matter content than conventional-tillage grain sorghum and wheat plots. Bulk density under the reduced tillage system was higher than with the conventional tillage system. However, saturated hydraulic conductivity (Ks) of the surface soil was increased by reduced tillage practices compared with conventional tillage. This may have been attributable to higher amounts of microaggregates and larger macropores under the reduced tillage system. Residue removal decreased the Ks of surface soil, especially in reduced-tillage grain sorghum and wheat plots. Microaggregation values were higher with residue retained than with residue removed (27.1 vs. 23.5 g kg-1 in dryland and 32.3 vs. 27.1 g kg-1 in irrigation). Results indicate that residue removal from Rolling Plains soils should be discouraged. Because of higher bulk density, use of a reduced tillage system may result in the need for occasional deep chiseling to reduce the effects of compaction.
