Adapted from articles by Joe Provey which appeared in Lawn Boy magazine.
Simplifying Turf Fertilization
Grasses require at least 16 different essential elements in their diets. Most of these are available from the surrounding environment, but the growth demands we put upon the typical suburban lawn are difficult ones. Having healthy grass usually entails helping Mother Nature along. Even if you are dedicated to having a low-maintenance lawn, you will need to fertilize with nitrogen to sustain thick, vigorous turf. In addition to bringing on deep green color, nitrogen is responsible for the sturdy growth and shoot density needed to fight off weeds and stand up to diseases, bugs, and traffic.
All of these positive effects can easily turn into negatives if excess fertilizer is used or if it is applied at the wrong time. The commonly followed practice of fertilizing in the early spring is actually not the way to go. It not only encourages excess blade growth, which means more mowing; it gives your weeds a boost and increases thatch! Excessive spring growth also produces thin-walled grass blade cells that are more prone to injury and disease. Mid-spring is the preferred time for feeding southern grasses.
In addition to nitrogen, your lawn may need phosphorus and potassium. Depending on where you live, your soil may naturally contain adequate levels of these elements. Aiding in root growth and improving germination rates, phosphorus (or phosphate) is needed in small amounts, and tends to remain in the soil. Potassium (or potash) is more prone to leaching, and plays an important role in enhancing your grass’s resistance to cold, disease, drought, and wear.
A fertilizer containing all three of these nutritional elements is called “complete.” The percentage of the bag that is made up respectively of nitrogen, phosphorus, and potassium can be found by looking at the fertilizer grade. These three prominent numbers also tell you the ratio of nitrogen to phosphorus to potassium. For example, in a 50-pound bag of 20-10-10 grade, the ratio is 2:1:1 and you will have 20 percent of the 50 pounds, or 10 pounds of the bag as actual nitrogen; 10 percent or 5 pounds as phosphorus, and 10 percent or 5 pounds as potassium. The remaining 30 pounds in the bag may contain additional elements such as iron and sulfur, as well as organic material known as “filler.”
In considering which bag of fertilizer is most appropriate for your yard, it is important that you read the back label for the guaranteed analysis of the contents. If your soil test indicates that you don’t need to add phosphorus or potassium, choose a bag where the grade has a low numeral or zero for that element. Aside from checking the grade, you should also determine whether the nitrogen is “water-soluble” or “water-insoluble.”
Grass plants can immediately use water-soluble nitrogen, once watered into the soil. Man-made ammonium nitrate, ammonium sulfate, and urea are examples of such quick-release forms of nitrogen. These provide a rapid green-up but have drawbacks. To spread the release of nitrogen over time, fertilizer companies manipulate the size of particles, and sometimes coat them as well. Because these forms take longer to dissolve, they release nitrogen at varying rates. While still water-soluble, they are called “slow-release.” Soil microbes must first break down water-insoluble nitrogen into forms grass plants can use. These truly slow-release sources include synthetic organics, like ureaforms, or those derived from natural organic materials, such as composted manure. When buying fertilizer, opt for the water-insoluble types or other slow-release forms. Using slow-release fertilizers will allow you to minimize the amount of time spent behind your spreader. They last much longer and don’t have to be applied as frequently.
Caution: many fertilizers have a combination of both fast- and slow-release types of nitrogen; check carefully to find products that derive a majority of their nitrogen from slow-release sources.
For low-maintenance lawns, you should be applying 1 to 4 pounds of actual nitrogen per 1,000 sqare feet per year. This may require adjustment given your specific growing environment, soil test results, the lawn’s condition, and type of fertilizer (slow- or fast-release). The fertilizer bag directions take into account what type of nitrogen is being used and the rate at which it should be applied. Follow the manufacturer’s instructions, and check the square footage of your lawn to ensure you are applying the appropriate amount. Remember, more is not better with fertilizers, as applying too much may “burn” your lawn as well as promote thatch formation and diseases. Leaving mulched clippings on the lawn over the course of a year will add about 1 pound of nitrogen per1,000 square feet, so figure accordingly.
Trim Time While Cutting Your Grass
The amount of time and money you spend maintaining your lawn depends a lot on what your idea of a lawn should be - not necessarily what your lawn actually needs. Early lawns of the Middle Ages did not require much maintenance. That’s because they were inspired by glades or grassy openings in the forest (not pictures in magazines or golf courses). These lawns were meadow-like mixtures of grasses and flowers that were planted amongst fruit trees, vines, flowers, and herbs, and enclosed by fences or courtyards. There was no mowing. Grass was kept from growing too tall by trampling it into a soft, woven, mat-like surface. If you too can adjust your expectations to taller grass, a mix of other plants in your turf, such as clover, and mid-summer periods when your grass temporarily turns brown, you can achieve a low-maintenance lawn - and one that’s closer to the original spirit of the lawn.
The right height. There are several reasons not to cut your grass too short. First, grass grows from the crown, not the blade tips. This trait makes grasses ideal for lawns because they keep on growing despite the regular mowing off of their upper stem, leaf sheath, and blades. This is also why it’s important not to damage grass crowns by accidental scalping with the mower. No crown, no grass! Second, keeping grass on the longer side also allows it greater surface area to carry out photosynthesis. This in turn results in healthier plants. Third, taller grass grows slower than shorter grass. You can use this simple fact to eliminate up to 20 percent of the mowing you do annually. That’s a savings of about 8 hours for the average lawn owner, not to mention a savings of gasoline and wear and tear on equipment. Finally, by keeping your grass at the high end of its recommended mowing height, you can prevent 90 percent of all weeds from germinating - and thereby eliminate the need for herbicides.
When to mow. Most cool-season grasses should be cut when they reach heights of 3 to 3-1/2 inches - typically once a week. Warm-season grasses should be mowed when 2 to 2-1/2 inches tall. Cut no more than 1/3 of the grass height at each mowing to avoid damage to plants. If the lawn grows too high for you to cut off 1/3 the height and have an acceptable length, cut off 1/3 now, and mow 1/3 off again in two or three days. Cutting more than 1/3 the height will cause grass clippings to lay on top of the lawn and decompose more slowly, and will give the grass a more open, bristly appearance. In addition, short cutting will stunt or slow root growth and weaken the grass plants.
What to do with your lawn clippings. Today’s advice, contrary to 20 or 30 years ago, is to leave clippings on the lawn. The old belief that clippings contribute to thatch build-up is false. Thatch is a build-up of roots and stems, not grass blades. Use a mulching mower, and leave clippings where they fall. It not only saves the labor of collecting and composting them, it also reduces the need for adding fertilizer to your lawn, and helps to conserve soil moisture. There are exceptions, however, to this advice. If you have neglected your mowing or must mow in wet conditions, the long clippings are likely to form heavy, soggy clumps that cover the grass. In such cases, the clippings should be removed so they do not smother the grass.
The idea of leaving clippings on the lawn is not new. In 1859, Henry Winthrop Sargent, a garden book writer and editor, wrote that “except during May and June when the growth of grass is more rampant, and has to be gathered, we have removed our box for catching the grass as it falls from the rollers, and permit it to fly in a little shower all over the lawn as the cutting progresses. In this way, the lawn-top dresses itself, by returning all that it produces.” Today’s new mulching mowers, also called recycling mowers, make it even easier to leave clippings where they fall. The deck and blade designs enable these mowers to cut each blade several times, producing a finely chopped clipping.
For further information on lawn care, contact Steve McCarthy, Section Editor, Lawn Boy magazine, at <firstname.lastname@example.org> or at (612) 861-5230, extension 14.
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