Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/1997
Publication Date: N/A
Interpretive Summary: Soil erosion and water runoff in the inland Pacific Northwest wheat fields are often severe during the winter. Rain or snow melt in fall seeded fields with frozen soil, long steep slopes and very little ground cover from crop residue are especially troublesome conditions. A two year field study was conducted to evaluate the technique of ripping contour infiltration channels (25 to 60 cm deep) in the late fall. Surface runoff was intercepted in these channels, the runoff moved below the frozen soil layer and infiltrated into the permeable subsoil. Ripping improved water infiltration, reduced soil erosion and did not influence grain yield. The results suggest that deep fall ripping in highly erodible fields or portions of fields in the inland Pacific Northwest seeded to wheat is an effective soil and water conservation practice.
Technical Abstract: Water runoff and soil loss from fall-sown wheat (Triticum aestivum L.) fields are often severe during the winter when rain or snow melt occur on frozen soils in the inland Pacific Northwest (PNW). In a 2-yr. field study near Benge, WA, we tilled seeded wheat plots on slopes >40% in late fall to a depth of 25 or 60 cm with shanks spaced 2.7 or 6.0 m apart. In a dry winter, no soil loss was measured in ripped plots compared to 3.0 t ha-1 soil loss for the control. Soil drying occurred near the tillage channels in ripped plots, reducing over-winter soil water storage. In a winter with higher than average precipitation and frequent frozen soil conditions, soil loss was 6.4 and 20.2 t ha-1 for ripped and control treatments, respectively. Ripping significantly improved water infiltration into the soil to a depth of 180 cm as far as 90 cm down slope from the tillage channel. In both years, grain yield was reduced in the row most disturbed by the tillage shank, but was increased in adjacent rows. On a whole-plot basis, there were no differences in grain yield between ripped and control treatments either year. Results suggest that deep ripping seeded wheat fields in late fall is an effective soil and water conservation practice which does not reduce grain yield.