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Regular Versus Reduced Herbicide Rates for Spring Barley

Eugene Butler
with Larry Smith, Nez Perce Co. Extension

Objective

Compare weed control and yield in spring barley treated with regular versus reduced herbicide rates.

Location: Culdesac, Idaho
Annual precipitation: 20 inches
Rotation: Pea, wheat, barley

Treatments

Reduced rate - 0.20 pint/ac MCPA applied in water adjusted to pH 4.2 using citric acid
Regular rate - 0.75 pint/ac MCPA (unadjusted water, pH 7.0)

Comments

The MCPA was applied on 5 May 94 to Harrington barley. Weed pressure was light, and there were no significant insect or disease problems. The plots were 50 by 800 ft. The regular herbicide rate was applied with unadjusted well water. The pH of the well water was adjusted to 4.2 before applying the reduced herbicide rate. An application of Roundup six days prior to planting for quackgrass control may have impacted weed pressure. By visual observation, there were good levels of weed control for both treatments.

Data

Barley yield, lb/ac

Treatment Rep 1 Rep 2 Rep 3 Average

Reduced 2239 1755 2662 2219a

Regular 2178 1876 2602 2219a

LSD (5%) 260

CV 3.3%

Conclusion

The regular and reduced rate of MCPA revealed no significant differences in grain yield of barley. Weed control in the two treatments may have been different without the preplant Roundup treatment.

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