INFILTRATION OF SIMULATED RAINFALL - TILLAGE SYSTEM AND CROP RESIDUE EFFECTS

Low precipitation limits dryland crop yields in semiarid regions. Irrigation can increase yields, but declining water supplies, competition for water, and high pumping costs have caused an increased emphasis on water conservation in many regions. Water conservation, however, often is hindered by soil surface conditions that cause runoff, even from small rainstorms. The objective of this study was to determine the effect of tillage system and crop residue [winter wheat, Triticum aestivum L.; grain sorghum, Sorghum bicolor (L.) Moench] treatments on infiltration of simulated rainfall on Pullman (fine, mixed, thermic Torrertic Paleustoll) soil at Bushland, TX. Treatments were moldboard plowing plus disking, rotary tillage, sweep tillage with residues removed, sweep tillage with residues left in place, no-tillage with residues removed, and no-tillage with residues left in place. Different tillage systems caused significant differences in soil aggregate size, aggregate stability, organic-matter concentration, initial water content, sediment loss during the rainstorms, bulk density, surface residue cover, and surface roughness. Compared with the no-tillage treatments, moldboard plowing usually caused the greatest differences in the soil conditions. There was no close relationship, however, between any soil condition and infiltration. With limited residues, soil-loosening tillage increased infiltration.