Influence of alternative and conventional management practices on soil physical and hydraulic properties

This study examined the effects of alternative and conventional farming practices on soil physical properties, including texture, organic C content, bulk density, moisture retention, and saturated hydraulic conductivity (K-s). There were no significant differences in soil organic C contents between the alternative and conventional management systems. Bulk density in the A horizon was 3% lower under alternative management practices (1.39 Mg m(-3)) than under conventional practices (1.43 Mg m(-3)). Saturated hydraulic conductivity was significantly higher in the A horizon under alternative management practices (45.5 cm d(-1)) than under conventional management (18.1 cm d(-1)). Differences in conductivity were greater for soils located at bottom-slope positions than soils at mid- or upper-slope positions. The b value of Campbell's moisture retention equation was significantly smaller for alternative practices than conventional management practices in the A, B, and C horizons. In the B and C horizons, the smaller b values could have been due to smaller clay contents in soils of the alternatively managed system. The Campbell equation air entry value was significantly larger for alternative practices (1.1 kPa) than conventional practices (0.79 kPa) in the A horizon. Differences in bulk density, air entry, and K-s between the alternative and conventional management systems were attributed to differences in crop rotations and nutrient or tillage management between the two systems. These results provide a useful database of soil physical and hydraulic properties that can be used by modelers to estimate the impacts of alternative agricultural practices on water movement and water quality.