Tillage and perennial grass effects on ponded infiltration for seven semi-arid loess soils

To test the benefits of no-till, we measured steady-state ponded water infiltration on a Pacific Northwest geo-climo sequence of seven semi-arid soils where no-till, conventional till, and perennial grass fields were in close proximity. Average infiltration was 30 percent greater under no-till and grass compared to conventional tillage, although variability among sites and years was high. This indicates that these practices can reduce the potential for runoff and erosion when measured over many sites, but might not at a particular site. Infiltration correlated positively with sand content (r = 0.75), negatively with silt (r = -0.78), but was not correlated with water stable aggregates because texture had a dominant effect. The number of years since tillage was positively correlated with infiltration, particulate organic matter, permanganate oxidizable C (active C) and organic C (r = 0.58, 0.70, 0.50, and 0.57 respectively). Among soil properties, organic C was positively correlated with active C, particulate organic matter, water stable aggregates, and silt (r = 0.92, 0.63, 0.38, and 0.41, respectively). Despite high variability and the need for numerous subsamples, measurement of infiltration was an effective test for documenting benefits of no-till. Additional research with correlated indicators appears warranted, but researchers should be cautious in assuming their relationship to infiltration.