NEW SPRAYER TECHNOLOGY NOW AVAILABLE FOR MANAGERS OF FOOD PLOTS

Part III: Sprayer Operations

 By W. Carroll Johnson, III
Coastal Plain Experiment Station
Tifton, GA
wcjohnsoniii@planttel.net

In Parts I and II of this series on ATV sprayers, we discussed basic sprayer concepts, set-up and calibration. The next step is sprayer operation - the point where you begin to recover the investment in an ATV sprayer.

Dilution and Mixing 

At this point, it is assumed that the nature and severity of the weed or grass problem is known, along with an appropriate herbicide needed to control the weeds. Carefully read the herbicide label, which in this context refers to the detailed instructions provided with the herbicide. The label also provides information on protective clothing when applying the herbicide. Protective clothing may be chemical resistant coveralls, boots, gloves and safety glasses. Pay close attention to all safety statements, for your safety as well as the safety of others.

The first step is to visually estimate or measure the size of the area treated, which will determine the volume of spray mixture needed to treat the area. Unless you have a knack for estimating area, simply measure or step-off the rough dimensions and calculate the estimated area in square feet (ft²), which can then be easily converted to acres (1 acre = 43,560 ft²). As a reference, the area of a football field is 1.3 acres. Once the size of the treated area is determined, retrieve the sprayer calibration value (gal./A) described in Part II of this series. Use the calibration value and the area to be treated to determine the amount of spray mixture needed for the task.

(acres treated) * (gal./acre) = gal. of spray mixture

Depending on the calibration, area to be treated and size of the spray tank, the task may require a partial tank or multiple fillings to treat the site. Add the calculated amount of clean water to the spray tank.

Example:   A food plot measures out to be approximately 1.25 A. You calibrated the ATV sprayer to spray 15 gal./A. and the tank has a capacity of 20 gal  The volume of spray water needed to treat the food plot is: (15 gal./A * 1.25 A = 18.75 gal.). Add 18.75 gal. of clean water to the spray tank.

The next step is to calculate the amount of herbicide and additives necessary for the area treated. The appropriate rate (dosage) is found on the herbicide label in the text section for the crop and weeds/grasses to be treated. Herbicide rates vary according crop, weed, grass, geographic region, soil type, etc. Always refer to the label to make sure you are using the herbicide correctly. The herbicide rate will usually be expressed in volume/A or weight/A, depending on herbicide formulation (liquid or dry commercial product). Using the published rate and area treated by the volume of spray water in the tank, the amount of herbicide to add to the spray tank can be calculated using the following equation:

(herbicide rate/acre) * (acres treated) = amount of herbicide to add to spray tank

Spray adjuvants (additives) are often needed for postemergence herbicides. Adjuvants are surfactants (wetting agents), crop oil concentrates and water soluble dyes for marking spray patterns. Many times, the adjuvant rates are listed as volume of adjuvant per gallon of spray water or percent concentration of total spray volume.  Refer to the adjuvant label for rates.

Example (cont.): Vantage is needed to control crabgrass in a planting of Imperial Whitetail Clover. The label lists the Vantage® rate at 2.25 pt./A. The food plot is 1.25 A. The amount of Vantage to add to the 18.75 gal of water in the spray tank is: (2.25 pt./A * 1.25 A = 2.8 pt.). A crop oil concentrate adjuvant is not needed with Vantage.

Always check and double check all calculations.  

Operations 

Once the herbicides and adjuvants are added to the spray tank, the contents of the tank need to be mixed. Some sprayers have bypass agitation, which is a means by which some of the herbicide mixture is circulated by the pump from the bottom of the tank to the top. This is adequate to keep herbicides mixed during operation, but not enough to outright mix spray tank components. Simply stir the contents of the spray tank with a piece of lumber or a stout stick.

Most agronomic crops including corn, soybean and sorghum are planted in rows. The row pattern makes it fairly easy for growers to keep track of where they have sprayed. Forages, whether for livestock or wildlife, are a different matter since they are either broadcast seeded or drilled like small grains, leaving few visual reference points for spraying. Managers of food plots have three options to keep track of where they have sprayed. One technique is to measure and mark the width of the spray swath across the field using surveyor flags. Simply drive and spray between flags across the field. Another technique is to use a dye specially formulated for use in herbicide sprays. In this example, the blue spray mixture is deposited on plant foliage, marking the area already treated. The last technique is to do nothing and guess at the previous spray swath using the tire tracks from the previous pass. This is not recommended since many herbicides have narrow margins of safety to the desirable crop plants and unintentional overlap of spray may seriously injure the crop.

Make every effort to ensure that you avoid grossly over-estimating the amount of mixed herbicide needed to complete the task. Given a choice, it is better to under-estimate than over-estimate the amount of mixed herbicide. This prevents the problem of disposal of extra mixed herbicide. Mixed herbicide needs to be used (sprayed) in an appropriate manner. Simply dumping the leftover contents of a spray tank is wasteful and environmentally irresponsible.

Clean-up and Storage 

Sprayer clean-up is an important maintenance step for the longevity of the ATV sprayer, since some pesticides are corrosive or foul the sprayer with herbicidal sludge. In addition, thoroughly cleaning the spray tank will help prevent contamination that may injure sensitive crops the next time the sprayer is used. This is particularly important with herbicides like Roundup and 2,4-DB. The standard protocol is to triple rinse the tank with clean water, thoroughly rinse the outside of the sprayer, and use a final rinse with an ammonia solution. The sprayer should be pressurized and operated for a few minutes to allow the ammonia solution to circulate and cleanse the lines and spray tips. It is a good idea to periodically remove and clean all spray tips and screens. If there is any doubt about the sprayer clean-up procedure, refer to the herbicide label for instructions.

An often-overlooked consideration with herbicides and other pesticides is storage. Avoid the temptation to stockpile herbicides. Buy the absolute minimum amount to do the job. The reason is obvious – safety to people and the environment. Eliminate the storage issue by not having any to store when you are finished with the task. If herbicides need to be securely stored, refer to the herbicide label for guidance. Always keep herbicides in the original container. Motor oil cans, soft drink bottles and milk jugs are not appropriate containers to store herbicides.

In conclusion, the ATV sprayer is a powerful and valuable tool to managers of food plots. Good weed and grass control is a readily achievable goal when judiciously used herbicides are used to back-up the foundations of good site preparation, stand establishment and a healthy forage crop. This is integrated weed/grass management. For all their advantages, herbicides and ATV sprayers come with a hefty responsibility. Be prepared. Be knowledgeable. Be careful.