Let us spray: Proper use of herbicides will save money

Special to The Post

If you sit around agricultural chemical retail outlets during herbicide buying season, you will hear a lot of griping about the prices.

As with other input costs, herbicide prices continue to increase. If used properly, however, they still provide more economical weed control than a shredder.

Gregory Clary and Larry Redmon of the Texas AgriLife Extension Service determined that 2.7 acres can be mowed in one hour with a 40-horsepower tractor pulling a six-foot rotary mower.

The same sized tractor equipped with a 30-foot boom sprayer can treat 14.18 acres per hour.

This means that five times more acres can be covered with spray in an hour than can be shredded.

Clary and Redmon calculated that herbicide cost is less than the extra fuel required to shred the same amount of ground.

Herbicides are cost-effective only if applied properly, though. Here are five tasks required to apply herbicides correctly are:

* Identify problem weeds.

* Select an herbicide that will control the identified weed species.

* Spray weeds at the right time.

* Calibrate the sprayer.

* Follow directions on the herbicide label.

Weed identification

It is necessary to identify your problem weeds in order to select the right herbicide. If you are not adept in plant identification, there are several ways to obtain assistance. One of the easiest ways is to ask your county agricultural extension agent to walk your pastures with you and help identify the problem weeds.

Web sites designed to help landowners with brush and weed identification were listed by Barron Rector during his presentation at the 54th Annual Texas A&M Beef Cattle Short Course. They include:

* rangeweb.tamu.edu/ctrp/public

* www.noble.org/webapps/plant-imagegallery

* www.geocities.com/sanansp/ index.html

* uvalde.tamu.edu/herbarium/ index.htm

* texnat.tamu.edu/htm

Dale Rollins, director of the Rolling Plains Quail Research Ranch near Roby, recommends scanning plants on a flat-bed scanner. He suggests digging an entire plant including its roots for the scan. Then send the scan to a state university or county agricultural agent for identification.

After the plant is identified, label the scan with the plant name, collection location and any observed growth characteristics. Keep your scans in a loose-leaf notebook for future reference.

Once plants have been identified, it is time to select the herbicide. There are two Texas A& M publications which list various weed and brush species with a recommended herbicide for their control: Texas AgriLife Extension Service bulletin B-1466 entitled Suggestions for Chemical Weed and Brush Control for Rangeland and Bulletin E-241, Suggestions for Weed Control in Pastures and Forages.

These two publications can be obtained from the county agricultural agent or by ordering through the Texas Agri-Life Bookstore website.

Spray at the right time

"We get the best bang for our weed control buck by spraying when weeds are small," said Melvin Poldrack. He owns and operates Poldrack Grain and Cattle Company at Coupland with his son, Terry, and grandson, Hunter.

"We spray the weeds when they are too little to reach with a shredder. This way, we get them before they start robbing moisture and nutrients from the grass,"Poldrack said.

Jeff Ball, agronomist with the Samuel Roberts Noble Foundation in Ardmore, Okla., agrees this is a sound strategy.

"When weeds are big enough to mow late in the growing season, there is no chance for optimum control," Ball said.

"Eliminating weed competition for nutrients and moisture in the spring is critical, since over 60 percent of the summer's forage is produced from May through June," Ball said.

Herbicide labels list optimum times to spray various weeds and these recommendations should be followed to obtain good weed control. Also refer to the label to obtain the correct rate of herbicide to apply.

Sprayer calibration

Proper sprayer calibration is a key component in obtaining economical weed control.

Using too much herbicide increases application costs and not applying enough chemical usually results in ineffective weed control, according to Texas AgriLife Extension experts.

Sprayer calibration can be a very confusing process, but Mark Matocha of Texas AgriLife Extension makes it very simple with his easy-to-follow step methods.

His calibration steps are slightly different for boomless sprayers than for boom-type sprayers.

Boomless sprayer calibration

* Measure the swath width.

* Use the table below to determine calibration course length.

* Mark the length of the calibration course and flag each end.

* Drive the course several times in the desired gear and at the desired rpm. Average your drive times and record the number.

* Park the tractor, maintain rpm used to drive the course and turn on the sprayer.

* Catch water sprayed from the nozzle into a bucket for the same amount of time that it took to drive the calibration course.

Measure the volume of water captured from the nozzle using a container graduated in pints. Pints of water caught in the bucket are equal to number of gallons the sprayer will deliver per acre

Matocha uses five simple steps to calibrate a boom sprayer.

Boom sprayer calibration

* Measure the nozzle spacing.

* Refer to table below for length of calibration course.

* Drive the course in the desired gear and at the desired rpm three or four times. Record your drive times and then average the numbers. The averaged number is the amount of time required to spray 1/128 of an acre.

* Catch sprayed water in a garbage bag from one nozzle for the time required to drive the calibration course.

* Pour the water from the garbage bag into a bucket and then measure the volume with a graduated container. The number of ounces of water caught in the container is equal to the number of gallons the sprayer will deliver per acre.

It is important to catch water from each nozzle to determine if all the nozzles are delivering the same volume. If the flow is uneven among the nozzles, examine each one to ensure that all nozzles, orifices and screens are the same size. Also check these parts for foreign particles that could impede flow.

The last principle in proper herbicide application is to follow the product label. Precautions and use recommendations on the label should be read thoroughly and used in the product application.

Optimum weed control can be obtained by using basic steps in herbicide application.