Crop residue management to trap snow and soil management to
improve water infiltration into frozen soil might reduce spring runoff
and increase soil water storage. We hypothesized that soil macropores
created by tillage would improve water infiltration when the soil was
frozen. This hypothesis was tested by ripping a Dooley sandy loam
(fine-loamy, mixed Typic Argiboroll) in the fall of the year and then
measuring water infiltration when the soil was frozen. A single subsoiling
shank was used to rip soil to a depth of 0.3 m at 6-m contour
intervals. Ripping was compared with no ripping using a randomized
experimental design having three replications. Studies were conducted
during 4 yr near Culbertson, MT, on plots seeded annually to spring
wheat (Triticum aestivum L.). Soil water was measured with neutron
attenuation and gravimetric methods. We used a constant-head (100
mm) method to measure water infiltration into frozen soil and a
rainfall simulator for unfrozen soil. Final infiltration rate on frozen,
ripped soil averaged 16 vs. 2 mm h-1 without ripping. Final unfrozen
infiltration rate in spring was 34 mm h-1 with ripping vs. 15 mm h-1
without ripping. Average spring water content of the top 1.2 m of
soil, to a distance 1.5 m downslope from a rip, was 32 mm greater
with ripping than without ripping at comparable slope positions. There
were no wheat yield differences between treatments. Contour ripping
can decrease water runoff, and seems best suited where spring runoff
and soil erosion caused by heavy winter snows is a problem
