QDMA Articles :
Increase Your Sprayer I.Q.

By: Brad Mormann and Dr. Grant Woods

As we wore out the road to our food plots, making trip after trip to refill the tank of our herbicide sprayer, we had plenty of time to ponder a question: “Is there a way to make each sprayer tank cover more acres?”

Establishing high-quality, weed-free food plots is a fabulous wildlife management technique. The ability to accomplish this goal is the result of the increased knowledge base of managers who realize that with food plots, quality is far superior to quantity. Luckily, we are in the age of Roundup Ready crops that allow us to quickly and effectively reduce weed competition by precisely timing and applying adequate glyphosate herbicide. There is also a wide range of more selective herbicides that allow us to kill unwanted grasses without harming the broadleaf plants in the same field, or vice versa, and there are pre-emergent herbicides that can kill weeds before they become a problem.

Almost everyone understands the usefulness of herbicide selection and application. However, selecting and operating the most efficient herbicide applicator for your needs can be more difficult and confusing. To fully understand the appropriate techniques for herbicide application often requires some research and trial-and-error. We want to describe some of the techniques and equipment we have learned about in our own process of trial-and-error that may help save you time and money.

The Initial Purchase
Like most food plot mangers would, we started our sprayer search by contacting local agriculture stores and surfing the Internet, looking for a tractor-mounted three-point hitch sprayer. As you would expect, price was a major factor in determining the right sprayer for our needs. After speaking with several sales representatives and wading through the often intimidating manuals and charts for sprayer design, the selection was made and a new sprayer, ready for use, was shipped our way. The question was, were we ready for it?

We set to work precisely following the manual’s instructions for sprayer calibration. During the calibrating process, we noticed that the operating speed most appropriate for our rough and rocky terrain did not register on the sprayer charts. The lowest speeds were 4 mph, but we cannot drive the tractor faster than 2.5 mph and still safely maneuver in our small and irregularly shaped food plots. This reduced speed caused more than just a problem with reading sprayer charts.

We determined that our broadcast flat fan No. 730308 sprayer nozzles, used at a pressure of 25 psi, would spray 26 gallons per acre. With the 110-gallon tank, we were able to spray 4.2 acres per tank. Since our property contains 50 acres of food plots, the tank had to be filled a minimum of 12 times to cover all of the Roundup Ready corn and soybeans. It took an average of two hours per fill, expending 24 man-hours at $10 per hour, using 1,320 gallons of water, not to mention tractor wear and tear and fuel consumption. In addition, finding windows of opportunity between spring rain showers for pre-emergence and post-emergence herbicide applications was difficult. Pre-emergence spraying readies the food plot for planting whereas post-emergence spraying removes established weeds in a crop. As you can imagine, we were quickly looking for alternatives.

Now that the limitation of speed on the sprayer and the costs associated with frequent tank refills had been determined, we began a more informed search for improving our sprayer’s efficiency. The sprayer nozzles or tips are what primarily separate one sprayer from another. Just like a hand-held power drill, the bit is what determines the tool’s use and effectiveness. In this case, the tip we started with was a very good one for avoiding herbicide “drift” because of the tip’s high spray volume and large droplets. However, the high spray volume was causing a high cost in labor and time per acre sprayed.

We found that many tip sizes are available. The tricky part is determining what tip is appropriate for the herbicides you are using. We generally use glyphosate, which is Roundup’s active ingredient. From our experience and conversations with other applicators, glyphosate can have a greater potential for plugging sprayer tips than most other herbicides. This, along with spray drift concerns, can limit the minimum size of a tip. Drift can be a very important factor in food plots surrounded by native vegetation or other plants that are susceptible to herbicide.

Sprayer Tip Flow Rate and Strainer Selection
As mentioned earlier, we were using a No. 730308 tip. The “03” stands for the tip’s output in tenths of a gallon per minute (gpm). This tip sprays 0.3 gpm at 40 psi. Switching to an “01” tip which sprays 0.1 gpm at 40 psi significantly reduced our sprayer output. We were able to switch to this much smaller tip by replacing the 50-mesh strainers ahead of the tips with 100-mesh strainers that filter finer particles. Strainers are essential to reduce clogging and excessive erosion of sprayer tips. The strainer numbers represent the number of openings per square inch. High mesh numbers have smaller openings than low mesh numbers. If these tip strainers begin to plug it may be necessary to add a single “line strainer” between the pump and the tips. It is much simpler to clean this single strainer on the main line coming from the pump than to clean all of the individual tip strainers. In general 100-mesh tip strainers are required for individual tips with a flow rate below 0.2 gpm, 50-mesh between 0.2 and 1 gpm, and no strainer over 1 gpm.

Angle of Application
The next consideration was the angle of the spray fan. A tip that sprays a broader fan would allow us to achieve more uniform weed suppression when the crops and weeds are taller. We chose a Turbo Tee-Jet 11001 tip that sprays at a 110° angle. In general, the greater the angle, the closer the spray tip can be to the vegetation while still achieving adequate coverage. This angle optimizes spray coverage when the sprayer tips are 20 inches above the sprayed vegetation. At this height above the crop and weeds, the spray sufficiently overlaps between fans to ensure uniform coverage and weed suppression. This also opens a larger window for spraying post-emergent herbicides. Remember, the key to post-emergent spraying is to spray when the crop is nearing canopy closure. This way the crop’s canopy will close before new weed seeds can germinate, effectively removing the crop’s competition.

Herbicide Drift Control
Finally, herbicide drift is a major concern when spraying in small food plots surrounded by plants susceptible to the herbicide in use. None of us enjoys the sinking feeling you get when you accidentally drift herbicide into an orchard of prized crabapple trees or a plum patch. Using glyphosate as the primary herbicide eases this selection process by allowing us to use a tip spraying medium-size droplets, yet still cover enough of the weed’s surface to optimize weed suppression. As you may already know, large droplet sizes lower coverage while also reducing drift, whereas small droplet size increases coverage and increases drift. Glyphosate’s excellent absorption and movement within the plant allows us to spray a smaller portion of the plant while still providing sufficient suppression.

Field Tested
After calibrating and testing the new tips under field conditions, we now spray 60 percent more acres per tank than with the original tips, saving time, money, and tractor wear and tear. Spray drift is always a concern but is minimized with a low spray pressure (25 psi) that creates larger droplet size yet enables uniform weed coverage.

Purchasing a sprayer and the appropriate tips for your purpose is as easy as contacting your local farm-supply outlet, talking to your local university Extension or USDA-NRCS agent, or searching on the Internet. Before selecting a sprayer setup, be sure to determine the type of herbicide you will be primarily using, whether it is a “kill-all” like glyphosate, a grass- or broadleaf-selective herbicide, or a pre-emergence herbicide. The individual herbicides can have drastically different performance in a particular sprayer setup. Detailed guidance on selecting tips appropriate to the specific herbicide can usually be found on the herbicide label, which you should be sure to read completely and follow closely when using any herbicide.

Although this process can seem tedious, learning from our mistakes will hopefully save you some time and money. A sprayer unit, whether mounted on a tractor, an ATV, or your back, can be an indispensable tool in a QDM and habitat-improvement program. Before you spend your money, determine the right sprayer combination that will be most appropriate for the jobs in your food plot To-Do list.




Quality Deer
Management Association
PO Box 160
Bogart, GA 30622
1-800-209-DEER (3337)


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