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The Situation
Reduced herbicide rates control weeds in grain. In an effort to
help farmers reduce production cost and lower the impact of pesticides
in the environment, research by University of Idaho weed scientists
has shown that weeds in small-grain cereals can be controlled with
below-label herbicide rates. Wild oat and broadleaf weed control
studies have been conducted the past several years using reduced
herbicide rates in irrigated barley and wheat.
The Result
Results of this research have shown that with accurate rates and
proper timing of application, many weeds can be controlled with
the most effective herbicides at rates as low as one-sixth to one-third
of the normal use rate. In wild oat populations greater than about
40 plants per square foot, the full rate or nearly full rate, was
more consistent than reduced rates, but in low to moderate infestation
levels below 40 plants per square foot, the reduced herbicide rates
performed very well. In addition, the number of weed seed returning
to the soil from surviving weeds was equal between the reduced rates
and the full rate. Grain yields in most of the reduced rate treatments
were equal to the full rates. In addition, quality of malting barley
was not affected by reduced herbicide rates.
These experiments
were conducted in cooperation with UI extension educators in six
counties across southern Idaho. The next step in this project is
to conduct on-farm large plot tests so that farmers can see for
themselves that weeds can be controlled with reduced herbicide rates.
One important point for the grower to keep in mind before trying
this concept is that when using an herbicide below the manufacturer's
labeled rate, they assume the liability for performance. Thus, it
will be important for growers to apply reduced rates accurately
and timely.
The Future
It is still too early to determine the full impact of this research.
However, grower response at field days and extension meetings has
been very favorable. Of course, some producers are a little skeptical
of using reduced herbicide rates, but that is not all bad. It is
best for a grower to try it on a portion of the crop the first year
than to adopt this concept for the entire farm. Adoption of reduced
herbicide rates for weed control in grain could lead to a savings
of $7 to $13 per acre in chemical costs with grain yields equal
to using full herbicide rates.
For more information
contact: Don W.
Morishita
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