Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: March 23, 2000
Publication Date: N/A
Technical Abstract: Reducing sprinkler droplet impact energy should minimize surface soil aggregate breakdown, seal formation, and subsequent crust development. Center pivots can be nozzled to apply some water at low energy until crop seedlings emerge, then re-nozzled to apply more water per pass until harvest. The objective of our 3-year field study in southern Idaho was to quantify the effects of sprinkler droplet energy on infiltration and near-surface hydraulic conductivity measured under tension after crop stand establishment. The treatments were droplet energies: 0, 7, and 15 J/kg. A low-pressure, lateral-move irrigation system produced droplets that impacted the soil surface with nominal energies of 7 or 15 J/kg. The 0 J/kg-plots were covered with nylon screen. In the spring, we planted sugarbeet (Beta vulgaris L.) into Portneuf silt loam (Durinodic Xeric Haplocalcid), then irrigated 2-3 times within 21 days after planting. After all seedlings had emerged, we measured unconfined (3-dimensional) infiltration rates through undisturbed soil surfaces above interior rows of either two or three treatments each year. Infiltration was measured at supply potentials: -60, then -40, then -20 mm of water. Steady-state infiltration rates were used to calculate unsaturated hydraulic conductivities at each potential. Reducing droplet energy significantly increased seedling emergence and visually kept soil surfaces rougher, depositing less soil and aggregate fragments in surface depressions. Preliminary findings also suggest that near-surface macropore conductivity was maintained since steady-state infiltration rates at -20 mm potential often increased as droplet energy decreased.