by Chris Hicks, County Director – UT Extension Smith County
As we head into spring, a lot of good things are going to be happening. Flowers will bloom, the trees will put on new growth, and livestock will shed their winter coat and trade in their diet of hay and commercial feed for new forage growth. On the flip side to all these nice things, troublesome weeds will also begin to make their presence known.
Weeds, which can simply be defined as plants growing out of place or where they are not wanted, compete with desirable plants for water, nutrients, and space. They decrease forage quality and inhibit growth of more desirable grasses or crops. The spines on some weeds such as cocklebur and thistle can irritate livestock and other weeds such as perilla mint and poison hemlock are toxic. Morningglory and other vines can make corn and soybean harvest difficult.
Weeds can be controlled in a number of ways and an integrated approach that includes good fertility management, mechanical and biological control when practical, and timely herbicide applications will yield the best results. When using herbicides, making sure your sprayer is properly calibrated is a critical step. An easy rule of thumb is 20X20, meaning at least 20 gallons of water per acre at 20 PSI should be applied to ensure good coverage.
Many of our available herbicides require only a few ounces per acre. Without knowing exactly how much water your sprayer is putting out, it is likely you are applying ether too little or too much chemical. Applying too little wastes money because the herbicide may not work. Applying too much wastes money because more product than necessary is being used. Applying too much can also damage desirable plants and lead to environmental consequences.
Calibrating the sprayer before use can be done quickly and easily using the 1/128 method. This method is based on the fact that there are 128 ounces in a gallon of water. Therefore, if we measure the output of a sprayer in 1/128th of an acre in ounces, that number is the equivalent of gallons per acre. This is done by measuring the time it takes to drive a specific distance based on your nozzle spacing. Then turn the sprayer on and measure the output from one nozzle for the time it took you to drive the course.
For example, if your nozzle spacing is 20 inches, you would measure 204 feet and drive that distance at the speed you would normally spray. If it took you 30 seconds to drive that distance, you would then park the tractor and collect water from one nozzle for 30 seconds at the same RPM you had been driving. If you collected 25 ounces, that means your sprayer is putting out 25 gallons of water per acre.
A similar method can be used with boomless nozzles. The only differences are your course length is based on the width of the spray swath, and the output is measured in pints instead of ounces. Both of these methods are covered in the UT Extension publication “A Simple Method To Calibrate Sprayers”, available online at smith.tennessee.edu. We also have an excellent video covering the topic that is available at utbeef.com.
Weeds can certainly be a problem with production and this season will probably be no different. While a healthy growing crop is a good defense against weeds most of the time, it may be necessary to use herbicides occasionally. Always refer to the chemical label and make sure your equipment is properly calibrated. If you have questions or would like assistance calibrating your sprayer, give me a call at 615-735-2900.
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