Return to Tillage Seeding Practices

Tilling Seeded Wheat Fields to Reduce Soil Loss and Increase Water Infiltration

Bill Schillinger, Dale Wilkins, Harold Clinesmith, Harry Schafer,
Craig Curtis, and Craig Cameron

Objective

To determine the effects of deep tilling fall-sown wheat on steep slopes prior to soil freezing on soil loss, water infiltration into the soil, and grain yield components and crop characteristics.

Location: Harold and Dorothy Clinesmith farm, Benge, WA
Annual precipitation: 12 inches
Soil: Walla Walla silt loam
Cropping pattern: Winter wheat-summer fallow

Treatments

Check - no tillage
Tilled - Plots were deep tilled with a subsoiler shank in late fall

Comments

Water runoff and soil loss from fall-sown wheat fields are often severe during the winter when rain or snow melt occur on frozen soils in the inland Pacific Northwest. Water infiltration rate of the silt loam soils in this region is about a half inch per hour, but approaches zero when the soils are frozen. In a 2-year field study, we tilled standing wheat on slopes greater than 40% in late fall to a depth of 11 or 24 inches with shanks spaced 12 or 20 feet apart.

In a dry winter, no soil loss was measured in ripped plots compared to 1.3 tons per acre 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 2.8 and 9.0 tons per acre for ripped and control treatments, respectively. Tillage channels generally stopped rills, whereas many rills extended the entire length of the hillside in control plots. Channels were filled with sediment by March.

Data

Cumulative soil loss (tons/acre) measured during the crop cycle in 1994
and 1995 at Benge as affected by ripping.

1994

Date	Control	Ripped	P-Value
6 January	1.2	0.0	0.021
23 March	1.3	0.0	0.013

1995

Date	Control	Ripped	P-Value
12 January	4.2	0.1	0.018
26 January	5.2	0.3	0.001
28 February	9.4	1.2	0.003
4 April	9.0	2.8	0.041

Conclusion

Tilling seeded wheat fields significantly improved water infiltration into the soil to a depth of 6 feet as far as 3 ft down-slope from the tillage channel (data not shown). 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 tilling seeded wheat fields in late fall is an effective soil and water conservation practice which does not reduce grain yield. These results agree with Clinesmith's personal experience tilling seeded wheat fields on his farm the past five years.

In areas of the PNW where soil freezing is common, growers routinely chisel or subsoil wheat stubble after harvest to reduce the risk of soil erosion and increase over-winter water storage. We feel growers will benefit by employing this management practice (with wide shank spacing) on sloping ground during the crop cycle as well. This research was funded by the Washington Wheat Commission.

Contact us: Hans Kok, (208)885-5971 | Accessibility | Copyright | Policies | WebStats | STEEP Acknowledgement
Hans Kok, WSU/UI Extension Conservation Tillage Specialist, UI Ag Science 231, PO Box 442339, Moscow, ID 83844 USA Redesigned by Leila Styer, CAHE Computer Resource Unit; Maintained by Debbie Marsh, Dept. of Crop & Soil Sciences, WSU