Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 6, 2000
Publication Date: N/A
Technical Abstract: Soil organic C (SOC) from dairy manure restores the productivity of eroded southern Idaho soils. SOC and/or irrigation may be altering these soils' hydraulic properties. We evaluated the effects of SOC and simulated center-pivot irrigation on infiltration and near-surface hydraulic conductivity measured under tension in recently roller- harrowed Portneuf silt loam, Durinodic Xeric Haplocalcid. The experiment was a split plot, in time, with two replications. The main plot treatments were pre- or post-irrigation while the subplot treatments were SOC contents, nominally 4.7, 8.7, or 11.4 g/kg. Field plots were irrigated using two half-circle spray heads that faced each other 6 m apart. Each head had a rotating, 6-groove spray plate, was 3 m above the soil surface, and was operated at 140 kPa nozzle pressure. In October 1998, we applied about 130 mm of water at a constant 70 mm/h intensity in a single irrigation to replicated, 1 x 2 m plots differing in SOC due to past years' management. We used tension infiltrometers to measure unconfined (three-dimensional) infiltration rates before and ca. 10 days after irrigation. Infiltration was measured through an undisturbed surface at three supply potentials: 60, then 40, then 20 mm of water. Steady-state infiltration rates were used to calculate unsaturated hydraulic conductivities at each potential. At 20 mm potential, steady-state infiltration was 13.6 micrometers per second before irrigation but 4.2 micrometers per second afterwards. SOC did not affect infiltration or hydraulic conductivity at any potential.