Reducing Herbicide Rates
When is it appropriate to reduce herbicide rates?
Reasons to consider reduced application rates
• A desire to cut costs of production • Concern about the environmental effects of herbicides • New regulations on herbicide use • Concern about herbicide carry-over
Methods of Application Tested
• Sprayer broadcasting over entire field at 100 percent of recommended level • Sprayer broadcasting over entire field at 50 percent of the normal label rate
– This method reduces herbicide use by 50 %
• Herbicide is sprayed in bands at 100 percent of the normal label rate.
– Herbicide rate is again reduced by 50%
• Herbicide is sprayed in bands at 50 percent of the normal label rate.
– Use of herbicide is decreased by 75% using this method
Possible concerns for the farmer center on the possibility of reduced yield if weeds are not controlled by the reduced-rate application.
Sound weed management programs include several components;
• • • • Mechanical cultivation Promoting vigorous crop competition Crop rotation Herbicide use
Additional factors must be considered:
• Cultivation, labor, and time must be available when needed.
– Herbicides degrade at a faster rate when applied at a lower rate. – Cultivation in a timely manner ( 30 to 40 days after planting) becomes critically important.
• This is more essential when there is no rain within 7-10 days after herbicide application
• Increased field management is required to accurately identify weeds, to monitor weather, and to ensure that weed cultivation occurs while the weeds are relatively small. • Reduced-rate herbicide applications do not provide adequate control for all situations.
– When facing weeds such as quackgrass full rates are needed. – Soils with cloddy surface or where a substantial amount of crop debris is present may not provide acceptable results.
• Herbicide manufacturers have no liability if the application rate is below specifications.
– Success depends largely on the farmer’s willingness to follow through with timely cultivation.
REMEMBER
• As with any new method, growers should try the reduced-rate approach on a limited basis at first, until they become comfortable with the methods and field management • Reduced application rates are not recommended if timely cultivation cannot be assured, or if there is a problem with hard-to-control weeds.
TEST TIME
One of the reasons to use reduced rates is to increase yield?
• A) true • B) false
Overall herbicide use can be reduced by 75% if the field is sprayed at:
• • • • A) 100% rate over entire field B) 50% rate over entire field C) 100% rate in strips only D) 50% rate in strips only
Cultivation for fields must be done in a _________ manner when using reduced rates.
Name one of the difficult to control weeds that would make full strength application necessary. ______________
Herbicide manufactures will stand behind their products if they are applied at less than recommended rates?
• A) true • B) false