How to reduce herbicide application rates
The soil health challenges of glyphosate use are becoming well known. Don Huber has reported that even a single application of ten ounces per acre is enough to alter the microbial community in favor of oxidizing – disease enhancing organisms.
I am not aware that any other herbicide is known to have the strong antibiotic effect of glyphosate, though each has it’s own set of environmental and public health challenges.
Some growers have figured out how to eliminate herbicides altogether. Other growers are still on the pathway of figuring it out.
Robotic weed control technologies are being developed that may make herbicides obsolete in the future, but they are not here yet.
Given this state of affairs, it would seem wise to figure out how we can apply the smallest amount of active ingredient possible and maintain or improve effectiveness.
When we describe designing nutrition applications, we find that we get the greatest performance when we use synergistic stacks of products from different categories, for example: bacterial inoculant, fungal inoculant, microbial stimulant, microbial food source, plant nutrients, plant stimulants.
We can use this same concept to reduce the required rates of herbicides. Some growers have reported reducing rates by upwards of 80% and maintaining effectiveness using a combination of different strategies.
The practices which are known to improve herbicide performance include:
- removing all minerals from the water, particularly carbonate and bicarbonate
- acidifying the water
- premixing the herbicide with a vegetable oil
- adding sugar to the spray solution
- adding fulvic acid to the spray solution
- structuring the water
Each of these practices increases the effectiveness of any material added to a spray solution (including foliar sprays). When we stack practices together, the improvement in results can compound.
When we stack these practices together, they need to be added in the right sequence, much the same as products should be added to a spray tank in the correct sequence. Here is the sequence that I have observed to be the most successful:
- Demineralizing the water, most commonly using reverse osmosis (RO). RO is very inexpensive for the reduction in active ingredients it can produce. This step alone can account for a reduction of 30-40% in product required.
- Structuring the water after it has been through an RO device and demineralized.
- Premixing the herbicide with vegetable oil 50/50 on a volume basis, and then add to the tank. The theory is that coating the compounds with vegetable oil will improve their absorption by the crop. I have some question marks about how this might work, and how much it actually does, but growers are reporting observable improvements.
- Add any acidifying agents to tank, such as ammonium sulfate. This may require much less than you expect when you use RO water to reach a low pH.
- Add fulvic acid to improve leaf absorption.
- Add sugar to contribute stickiness, and improve leaf absorption.
Exercise caution when using this approach with selective herbicides. The applied products will be much more effective, and can easily damage the non-target species. Test how much application rates need to be reduced, they will almost certainly need to be reduced to avoid burn.
I have observed complete weed control with 8 ounces of RoundUp per acre, roughly 4 ounces of active ingredient glyphosate per acre.
What practices have you used to reduce application rates while improving effectiveness?