INFILTRATION CHARACTERISTICS UNDER NO-TILL AND CLEAN-TILL FURROW IRRIGATION

Tillage or the lark of tillage affects infiltration and its variabilit y across the field. To quantify infiltration characteristics of soil u nder no-till and clean-till furrow irrigated systems, a 3-yr rotation of wheat (Tritium aestivum L.)-sorghum [Sorghum bicolor (L.) Moench]-f allow on a Pullman sandy clay loam soil (fine, mixed, thermic Torrenti c Paleustoll) was initiated. Treatments were no-till and clean-till wi th or without wheel traffic. Soil water contents, water advance times down the furrow, wetted cross-sectional area of flow, and cumulative f urrow infiltration during three irrigations for each cropping event we re determined. No-till treatments conserved significantly more soil wa ter (3.0 cm) during the fallow periods than clean-till. Average water advance times to the end of the field were 301 and 175 min for no-till and clean-till, respectively. Wheel traffic significantly decreased a dvance times, by a factor of 1.98, during the initial irrigations at p lanting with no effect on subsequent irrigations. Wetted cross-section al area in no-till furrows was significantly greater than in clean-til l during sorghum irrigations, averaging 0.0206 and 0.0093 m(2), respec tively. However, these factors did not contribute to a consistent incr ease in infiltration in the no-till treatments. Grain yields for sorgh um were significantly greater in no-till than clean-till: 4147 and 358 4 kg ha(-1), respectively, but clean-till wheat yields (5414 kg ha(-1) ) were significantly greater than no-till yields (4657 kg ha(-1)). No- till conserved more water during the fallow periods, but surface chara cteristics of planting wheat no-till in sorghum residue may decrease u niformity over long furrows.