Reduced herbicide rates
Using lower-than-recommended herbicide rates was the theme of the recent 1994 Expert Committee on Weeds meeting in Saskatoon, where participants heard it is common practice in Arkansas.
Variables including weed population and cost of inputs are entered in a computer model, which then makes herbicide recommendations, based on the yield loss farmers are prepared to absorb.
Complaints to industry sales representatives have not increased and there have been no lawsuits when the model is used. It was made clear, however, that producers use reduced rates at their own risk.
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Advantages of lower rates:
- Reduced input costs.
- Fewer applications made.
- Reduced carryover and injury from residues.
- Reduced amount of product in the environment.
- Potential for reduced weed resistance development.
- Producers become better managers and more knowledgeable about crop protection.
Disadvantages of lower rates:
- More intensive management required.
- Added risk accepted by producers.
- Window of application/timing is narrower.
- If first application is not adequate, may need a second one.
Some of the agronomic practices that help make reduced herbicide rates work are already being used by some producers.
Cultural weed control methods such as row spacing, timing of seeding and seeding rates to reduce weed competition are important factors in the effectiveness of reduced herbicide rate practices. Producers will need to become more familiar with economic thresholds or returns, learning to live with certain levels of weed populations in their fields if it is not economical to apply herbicides.
From the industry perspective, label rates are based on what works over a wide geographic area with a variety of environmental conditions. There is some rate flexibility depending upon where the product is used, the environmental conditions and the producer’s level of tolerance for weeds. The biggest issue is who, if anyone, is liable if the rates don’t meet the producer’s expectations.
Reduced herbicide rates do not necessarily mean a producer will spend less money on weed control in any given year. What is saved by reduced rates in one field may go toward weed control in another.
Reduced rates are used in Western Canada but rather than guessing at the rate, one Saskatchewan farmer said he would like some guidance: “Why not give us the maximum effective rate for a herbicide and let producers find the minimum rate that will work in their fields, under their growing conditions?”
– SWP Production Perspectives
