RAIN INFILTRATION AS AFFECTED BY WHEAT RESIDUE AMOUNT AND DISTRIBUTION IN RIDGED TILLAGE

Texas South Plains production systems for conserving rainfall and redu cing wind erosion in cotton (Gossypium hirsutum L.), a low-residue cro p, include the spring chemical termination of winter wheat (Triticum a estivum L.) overseeded post-harvest into cotton. This practice often i ncreases cotton lint yields under irrigation, but residues hinder weed control and increase production costs. This study characterized infil tration response to (i) residue weathering and soil consolidation with ridges, (ii) residue distribution on the ridge or in the furrow, and (iii) Bat or standing architectures and residue amounts. Simulated rai n was applied at 65 mm h(-1) for 1 h into a bare Olton clay loam (fine , mixed, thermic Aridic Paleustoll). Mean cumulative infiltration was lowest for bare soil (28.7 mm), but increased curvilinearly with incre asing residue amounts, leveling at 49.0 mm. Cumulative infiltration wi th residues distributed on the ridge (42 mm) or in the furrows (44 mm) were the same even though water in the furrow absorbed drop impact. A minimum amount of residue (0.7 Mg ha(-1)) to intercept raindrop impac t was needed to increase rain infiltration, but increasing residue abo ve a residue threshold of 2.4 Mg ha(-1) had no effect because of suffi cient drop impact interception. Increases in infiltration were related to the residue amount rather than to the bed or furrow location. Part ial residue cover and tillage operations that lodge crop residues may increase infiltration.