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Reduced Herbicide Rate on Winter Wheat

Cecil Martin
with Larry Smith, Nez Perce Co. Extension

Objective

Test effect of reduced herbicide rate on weeds and yield of winter wheat.

Location: Culdesac, Idaho
Annual precipitation: 18 inches
Rotation: Wheat/pea

Treatments

Harmony Extra Bronate Hoelon Excel 90 spreader StaPut

Regular rate 0.4 oz 1 pt 1 pt 3.2 oz 1.6 oz

Reduced rate 0.2 oz 1/2 pt 1/2 pt 3.2 oz 1.6 oz

Comments

The pH of the water used for the reduced rate application was lowered to 4.9 with citric acid, while the water used for the regular rate treatment was left at pH 7.0. The weed spectrum was mustard, tar weed, wild oat, gromwell, lambsquarter, and starthistle. Weed pressure, rated from 0 to 100% ground cover inside a randomly placed two-square-foot hoop, was 80, 80 and 50% for the reduced rate plots, and 70, 60, and 40% in the regular rate plots. These ratings were performed on 15 April 94, the same day as the plots were sprayed. The temperature was 68 F and the wheat was at Feke's 4 and 8.5 inches tall. The weeds were 1 to 3 inches tall. Wind direction was lengthwise to plots at 10 mph. A 10 square ft tarp was placed in each plot for weed control/suppression comparison. Plots were 22 by 300 ft.

Data

**Yield,** bu/ac
Treatment	Rep 1	Rep 2	Rep 3	Average
Regular	22	33	33	29a
Reduced	20	32	33	28a
LSD (5%)				2.5
CV				2.5%

Conclusion

There was no significant difference in grain yield between regular and reduced rate herbicide applications.

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