Prescription for a healthy turf
  Proper watering, fertilization and mowing help maintain a verdant lawn

 

March 18, 2004

Loretta Johnson and Brice Pavlish
Victoria County
Master Gardener Association Interns

There are so many people questioning why their lawns look poor, weak, or even have dead or dying spots. Turfgrass health is dependent upon proper care that maximizes root growth. The health of your turf rests on its ability to resist disease and handle stress. Root-healthy culture requires proper watering, fertilization and mowing. Although turfgrasses can appear to thrive on improper care, they will not sustain good year-round health and vigor.

Irrigation is one of the most basic practices, but is also the one most often done incorrectly. Shallow frequent watering promotes shallow root growth. Turfgrasses should be watered more deeply and less frequently. Water to provide moisture equivalent to one inch per week in hot dry weather - or moisture to a depth of six inches. Repeat only as signs of drought stress appear. Early morning is the best time to water. Late evening watering makes turfgrass more susceptible to disease. Over-watering can lead to wet wilt, leaching and loss of nutrients, and polluting runoff. Check your sprinkler or irrigation system to avoid loss of water from wind shift and runoff.

Lighter grass color is not necessarily an indication of poor plant health, but rather an indication of the lack of essential elements. Light color is usually a sign of a shortage of nitrogen, but can also result from a shortage of micro-nutrients such as iron and zinc caused by an overabundance of phosphorus. Establish a fertilizing program, and don't let grass color influence your fertilizer applications.

Begin your fertilizing program by soil testing, which can be obtained through Texas Cooperative Extension. Contact the Victoria County office for containers and mailing information. Best repeated every 3 - 5 years, these tests will analyze for soil pH, major nutrients as well as micro-nutrients and will give recommendations for your specific site.

The three major nutrients required by grasses are nitrogen, phosphorus and potassium, listed in order on bags of fertilizer. An example would be 21-7-14. This would be known as a 3-1-2 NPK ratio, N for nitrogen, P for phosphorus and K for potassium. In this case it would contain 21 percent nitrogen, 7 percent phosphorus and 14% potassium by weight. A 40 lb. bag then would contain 8.4 lb. of nitrogen, 2.8 lb. of phosphorus and 5.6 lb. of potassium. The label will also quantify the relative amounts of readily available (soluble) nitrogen and slow release nitrogen.

Some fertilizers are advertised as slow release. A fertilizer with 50 percent slow release is most desirable. If this is unavailable, you might consider using the lower nitrogen organic fertilizers. These are easier to apply because higher spreader feed rates can be used. Organic fertilizers are slow release and not as susceptible to nitrogen leaching and runoff. These are particularly good for sloping lawn areas.

For home lawns, the Texas Cooperative Extension recommends application of no more than 1 pound of soluble nitrogen per 1000 square feet of lawn at 8-10 week intervals, if needed - that means if your grass is showing deficiency symptoms. That is only three times per year - if needed. One or two applications may even be enough for some yards. More frequent fertilizing is not needed. The first fertilization should not start until around mid-April. This assures active growth for warm season grasses and allows for some die-off of winter weeds before fertilizing. Final application can be made between mid-September up to mid-October. However, applications should be reduced to one-half rate of normal or 1/2 lb. of nitrogen per 1000 square feet of lawn after September 1st. Over-fertilizing after September can just promote brown patch disease.

To illustrate that the application rate of 1 pound of readily available nitrogen per 1000 square feet of lawn is a light application of fertilizer, let's look at an example of actual lawn area in an 85' X 170' lot, 14, 450 square feet or approximately 1/3 acre. Subtract from that the square feet of non-lawn areas to determine square feet of lawn: House - 1980 square feet, garage - 538, patio - 420, driveway - 720, sidewalks - 364, and landscaping beds - 425. So the total lawn area is 10,013 square feet.

Let's use that same 40 lb. bag of 21-7-14, 50 % slow release fertilizer. 10,013 square feet divided by 1000 square feet is approximately 10, so we would apply 10 X 1 lb. of nitrogen or 10 lb. We found that the bag contains 8.4 lb. of nitrogen, so we would need to apply 1.2 bags on the entire lawn area! It's better to put on less than more, so in this case one bag would be sufficient.

More is not better. Fertilizing at an arbitrary rate per 1,000 square feet or so many times per year is strongly discouraged for a number of reasons. You are likely over-fertilizing. It potentially increases leaching and runoff, a major source of pollution in our streams and rivers. Over fertilization wastes your money and time and requires more frequent mowing and watering. Also, excess nitrogen will be converted to leaf growth at the expense of root structure growth, resulting in less resistance to drought stress, insects and disease. It promotes increased thatch buildup, promotes fungal diseases such as Brown Patch and Take-All Patch, and will increase already high non-reversible levels of phosphorus which can lead to plant deficiencies of iron and zinc. To further emphasize this point, a recent soil testing campaign promoted by the Victoria County Master Gardeners indicated 75 percent of the Victoria area samples were already too high in phosphorus from over fertilizing.

Mower height for St. Augustine grass is ideal at 2-1/2 to 3 inches. Increase the height in shady areas to compensate for the lower light by providing more leaf surface. Mow Bermuda at a height of 1-1/2 to 2 inches. Never remove more than 1/3 of the leaf growth at one time. Scalping exhausts the plant's food reserves and should not be done.

Do not bag grass clippings. Allow the cuttings to return to the lawn. They provide natural fertilizer with a NPK ratio of 3-1-2, just like your fertilizer. Clippings will not increase thatch buildup if proper mowing frequency is maintained, but can lead to too high nutrient levels and even possibly disease problems if you indiscriminately over-fertilize.

Good lawn care practices will minimize the risk of significant damage from disease and insects which are increased in stressed lawns. Grubs, chinch bugs, weeds, brown patch and take-all patch are pests that can be a problem in the Victoria area. For help with these problems contact your County Extension office.

So there you have it. This is the third and final article on turfgrasses for this spring. The articles were intended to provide a factual overview for growing turfgrass in Victoria. Hopefully you have found them helpful. Happy gardening!