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Comparing Fall Tillage Options for Improving Moisture Infiltration

Determine if fall tillage treatments following winter wheat production will improve soil water infiltration and the following winter wheat yields.

Location: Asotin Co, WA, Anatone Flat Average annual precipitation: 15"
Rotation: winter wheat-summer fallow Soil: Pataha-Niessenberg silt loam and Stember silt loam

Check - no fall tillage
Fall chisel
Fall subsoil

Six ounce/ac Roundup was sprayed before the stubble was lightly disked (1-2 inch depth). The fall chisel plots were then chiseled to eight inches on one-foot spacing with straight points. The subsoil plots were subsoiled to 13 inches on 30 inch spacing. In the spring all three treatments received a Roundup application followed six weeks later by chiseling 6 to 8 inches deep. In August, cultivation and fertilizer application were performed in one operation. Fertilizer rates were 45 lb N, 10 lb K, and 10 lb S per acre. Stephens winter wheat was planted with a Great Plains deep furrow drill with 15" row spacing. Starter fertilizer was 10 lb N, 12 lb P, and 1 qt "super starter" micronutrient per acre. In the spring Uran (5 lb N/ac) and "harvest plus" micronutrient was applied. The plot size was 40' x 2000'. The plots were harvested July 25, 1994.

Available soil moisture (inches) on 4 Oct 93, in top 2 feet. This sample was taken in fall following the fallow period.

Treatment	Rep 1	Rep 2	Rep 3	Rep 4	Average
Check	4.9	4.4	4.8	6.0	5.0a
Fall chisel	5.1	4.7	5.9	5.1	5.2a
Fall subsoil	4.7	3.9	5.8	4.7	4.8a
LSD (5%)					0.9
CV					10.5%

Winter wheat yield, bu/ac

Treatment	Rep 1	Rep 2	Rep 3	Rep 4	Average
Check	48.5	50.7	51.0	47.5	49.4b
Fall chisel	43.5	44.3	48.2	48.4	46.1a
Fall subsoil	45.0	46.6	48.0	47.1	46.7ab
LSD (5%)					2.8
CV					3.4%

Total available soil moisture (inches) on 18 Mar 94, in the top 2 feet during the winter wheat crop.

Treatment	Rep 1	Rep 2	Rep 3	Rep 4	Average
Check	4.8	4.2	4.7	6.4	5.0a
Fall chisel	4.5	4.8	4.7	5.2	4.8a
Fall subsoil	5.2	4.7	4.9	5.4	5.1a
LSD (5%)					0.7
CV					8.8%

Conclusion

During the droughty years that this study was conducted, there doesn't appear to be any improvement in soil moisture by either fall chiseling or fall subsoiling. The final winter wheat yields tended to be lower with the chisel or subsoil treatment when compared to the check.

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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