Fall Contour Ripping Increases Water Infiltration into Frozen Soil

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.