Applying Over-the-Counter Lawn Care Products Correctly

Prior to the purchase of over-thecounter (OTC) products, homeowners need to give some thought about their lawns, gardens, and flower beds. If the task for the day is to apply a fertilizer treatment, it would be helpful to know what the soil is deficient of, if anything. Do you routinely apply lime without knowing what the soil pH is? Are you confident the product you purchase will do what the label indicates? The results of this question are highly dependent on the next question. How do you apply these products confidently?

Two basic steps, soil testing and measuring the square footage of your lawn will make things easier. Part of applying OTC lawn care products correctly is to know if products are even needed or not. Measuring the square footage of your lawn is simply onetime procedure to purchase only what you need, without second guessing.

A routine soil fertility test (pH, neutralizable acidity, phosphorus, potassium, calcium, magnesium, organic matter, and cation exchange capacity) is recommended every two or three years for established turfgrasses. Obtain a Horticulture Soil Sample Information form, MP 555, from your local MU Extension center or on the Web. For additional information refer to MU Guide G6954 – Soil Testing for Lawns. Take the soil sample to your local Extension Center or send the sample to the following address:

Soil and Plant Testing Laboratory
23 Mumford Hall
University of Missouri
Columbia, MO 65211

Area measurements and mapping a lawn should be the first step in any home lawn care program. It is essential to know the square footage of your lawn in order to make accurate applications of fertilizers and other lawn care products. The most commonly used area measurements are square feet (sqft) and acres (ac). Most home lawns can be measured up in units of 1,000 sqft.

Calculating area can be accomplished using very simple applications of geometric figures (rectangles, triangles, or circles).

Geometric figures:

• Rectangle: Area = length x width
• Triangle: Area = (length of base x height) / 2
• Circle: Area = 3.14(radius)2

• For fertilizers or pesticides to be effective, they must be applied uniformly at recommended rates.
• Equipment (sprayers and spreaders) must be calibrated to ensure adequate application.
• Misapplication wastes time, material and money, and may harm the applicant or the environment.
• Liquid application equipment should be calibrated with plain water.
• Granular applicators (spreaders) must be calibrated with the actual product.

Proper use of fertilizers and pesticides, whether of synthetic or natural origin, contributes to healthy plant growth. Applying too much may cause foliar burns or other toxic reactions in the plant. Using too little may result in damaged plants from inadequate pest control or nutrient deficiencies.

The only way to know just how much fertilizer or pesticide is being applied to the plants in your yard is to calibrate the application equipment. Calibrating application equipment is relatively simple.

This guide outlines the steps for calibrating sprayers used for liquid applications and lawn spreaders used for dry products. Always read and follow the product label. Be sure to follow all safety precautions and wear proper clothing, rubber gloves, etc. as specified by the label.

Steps in calibrating a pump-up sprayer

• Adjust the nozzle opening to give the type of spray pattern desired. For hose-end sprayers, adjust the setting to the recommended dilution rate on the product label.
• Add a measured amount of plain water to the sprayer or concentrate canister. Use an amount equal to about half the sprayer's capacity.
• Pressurize the sprayer. Hand pump canister sprayers or turn water on for hose-end sprayers. Most canister sprayers do not have a pressure gauge. You can tell if you are maintaining a constant amount of pressure by the feel of the tension on the plunger.
• Spray the water onto a hard, flat surface such as a driveway. Use the same walking pace you would if applying actual pesticide. Make certain the water is applied uniformly, with no gaps and with only a small amount of overlapping.
• After the spray canister is empty, or when the concentrate container of the hose-end sprayer is empty, measure the area covered by the water.

• Calculate the amount of liquid coverage per unit area, and record that value for future reference.

Hose-end sprayer example
One-half cup of water in the concentrate container covered 1,200 square feet when diluted. 1/2 cup = 24 teaspoons, so each teaspoon covered 50 square feet (1,200/24).

• Measure the area to be sprayed and calculate how much spray will be needed. Mix only the amount of chemical needed to do the job. For large areas, mark off sections with flags to break the yard up into areas no larger than can be covered by one tank full of spray. Liquid calibration tips
• Rate of liquid applied varies with pressure and size of nozzle opening. Maintain constant, adequate pressure. Keep nozzle clean and setting unchanged for variable nozzles.
• Avoid excessive spray overlap. Overlapped areas get a double dose. A small overlap is necessary to prevent unsprayed gaps. If good spray coverage is questionable, cut the application rate in half and apply to the same area twice at right angles to one another. Let the first application dry before applying the second.
• The spray pattern should be continuous and uninterrupted. Keep your walking rate and sprayer wand arm movement constant.
• Direct the spray pattern away from the applicator. Avoid walking through the spray.
• Never spray on a windy day. Air movement above 10 miles per hour may cause undesirable drift.
• Keep a separate set of measuring spoons and cups for pesticide use only. Do not use them for any other purpose.
• Use a separate sprayer labeled "weed killer only" or "herbicide only" for weed control products.
• Wear appropriate protective clothing. A long-sleeved shirt, long pants, rubber gloves and water-proof footwear are recommended. Protective eyewear may be necessary. Check the product label for requirements.
• On trees, shrubs and other upright growing plants, spray until the pesticide solution begins to drip from the leaves. Spray the underside of leaves as well as the top.
• Clean sprayer thoroughly after each use.

Calibrating spreaders
Homeowners have a wide variety of spreaders to work with - some drop type, some rotary type, some listed on the product label for recommended settings, and many that are not. Rotary type spreaders are the best option in the application of lawn care products. They make applications easier, due to the fact that you do not need to worry about coming back precisely on your previous wheel marks. Rotary spreaders also require fewer passes to cover your lawn.

The best approach for homeowners does not necessarily involve the actual calibration of their spreader, but a more common sense approach to applying lawn care products. First, you need to accurately measure the square footage of your lawn and then purchase the correct amount of lawn care product. Second, evenly distribute that material over the total square footage. For example, you measured your lawn to be 10,000 square feet. The lawn care product you purchase states that, the contents of this bag covers 5,000 square feet. Therefore, you require 2 bags of this product to cover 10,000 square feet. You may ask now, what is the best technique to evenly distribute this product. Even distribution is usually assured with multiple passes in multiple directions over your lawn. Therefore, place your spreader on a light setting and continue to make passes over your lawn, changing directions with each pass until all the required material has been applied. This may require 3, 4, 5 or more trips over your lawn, but you can be certain that the distribution of the material is very good. In time, as you become familiar with your spreader and the products you use; you can fine tune your spreader to reduce the number of trip required.

Most fertilizers and lawn care products have tables on their bags with suggested settings for various brands of spreaders. If you are fortunate enough to own a spreader specified in the table, then; use that setting. Keep in mind that those settings are usually for one pass over the lawn. These application tables also assume a 3 mph walking speed. To give uniform applications, consider cutting the setting by 1/3 to ½, making two to three applications to avoid skips. This might be a way to decrease the number of trips you have to make with the above method.

For those wishing to know specific calibration techniques of rotary spreaders, please refer to MU Guide Sheet WQ551 - Calibrating Home Garden Equipment at http://extension.missouri.edu/explore/envqual/wq0551.htm.

Granular calibration tips