Sprinkler droplet energy degrades surface soil structure. Modifying
sprinkler irrigation systems to reduce droplet energy may reduce surface
sealing and crusting, thereby increasing emergence. From 1997 to 2001,
we evaluated the effects of sprinkler droplet kinetic energies of 0, 8, and
16J kg-1 on in situ surface penetration resistance (PR, a measure of crust
strength), aggregate stability (a measure of a soil's resistance to breakdown),
and water-stable aggregate size distribution, expressed as a mean
weight diameter (MWD). Each year near Kimberly, ID, we planted
sugarbeet (Beta vulgaris L.) into an initially tilled field of structurally weak
Portneuf silt loam (Durinodic Xeric Haplocalcid), then irrigated two to
four times using a lateral-move sprinkler system with spray heads having
either smooth or spinning, four-groove deflector plates. After the first
and last irrigation each year, we measured PR in situ and collected soil
samples at the surface, 0 to 6 mm. When measured after one irrigation,
PR increased, and aggregate stability generally decreased as droplet
energy increased, although the magnitude of the response differed from
year to year. After multiple irrigations, PR decreased linearly with
increasing droplet energy, likely due to erosion of the crusted surface.
Five-year average MWD after multiple irrigations decreased by 10%, to
0.42 mm, with droplet energies of 8 J kg-1 or more. Trend analysis of
soils data from 1998 to 2001 revealed that droplet energies ~10.6 J kg -1
decreased MWD most. Producers should reduce sprinkler droplet kinetic
energy to <10.6 J kg-1 to minimize surface structural breakdown of
recently tilled soil
