LAWN FERTILIZATION IN TEXAS
Adapted from an article by: R. L. Duble, James A. McAfee, and A. C. Novosad Extension Turfgrass Specialists
Lawn quality is generally measured in terms of color, density and uniformity. Cultural practices, particularly fertilization, largely determine lawn quality. A fertilization program should include timely fertilizer applications in amounts and formulations that meet the requirements of your lawn. Excessive nitrogen applications stimulate production of leaves and stems and increase the mowing requirements. Higher water requirements, increased thatch and increased susceptibility to insects and diseases also results from excessive application of nitrogen. Poor timing of fertilizer applications,such as mid-summer and early fall applications of soluble nitrogen, also increases the likelihood of chinch bug and brown patch problems in St. Augustine lawns.
Soil tests provide information on the availability of major fertilizer nutrients. Soil tests also suggest the need for lime or other amendments to correct soil acidity, soil salinity
or alkali soil conditions.
Environmental conditions such as shade, soil type and rainfall also influence fertilization requirements. Moderately or heavily shaded areas should not be fertilized
as much as areas in full sunlight. Grass growing in shade is more succulent and has a weaker root system than grass growing in full sunlight. Fertilizer tends to make the
grass more succulent and increases its susceptibility to disease, drought and other stresses. Nitrogen fertilizer also stimulate leaf growth at the expense of the root
system. St. Augustine growing in moderate to heavy shade should be fertilized in the spring and fall only, at a rate of 1 1/2 pounds of nitrogen per 1,000 square feet.
Turfgrasses growing in sandy soils require more frequent applications of nitrogen than those growing on clay soils.
Lawns in areas subject to high rainfall require more total pounds of nitrogen per year(the higher numbers in the above table) than lawns grown under dry conditions (the
lower numbers in the table). Thus, St. Augustine lawns in East Texas may require 4 to 5 pounds of nitrogen compared to 2 to 3 pounds in Southwest Texas.
Mowing practices, such as regular removal of grass clippings, also influence fertilizer requirements. Grass clippings contain 3 to 4 percent nitrogen on a dry weight basis,
which is recycled through the soil if grass clippings are not removed. Regular removal of grass clippings will add at least one fertilizer application annually to lawn
Timing and distribution of fertilizer applications, as well as rate of application, are important considerations in a lawn fertilization program. Timing applications to corresponds to grass requirements rather than to the convenience of the homeowner can reduce maintenance problems (figure 1). Generally, spring and fall fertilizer applications are adequate for St. Augustine lawns. Colorado County lies somewhere between region 4 and 5, so you can generally take the average of the two dates.
In early spring there is usually enough residual nitrogen to maintain grass through several mowings. The first application of fertilizer should be made after the second or third mowing.
If the lawn appears vigorous and healthy at that time, delay the first application until May. In the absence of soil test information, apply a fertilizer with a 3-1-2 or 2-1-1 ratio at a rate equivalent to 1 pound of nitrogen per 1,000 square feet.
Bermudagrass lawns require supplemental applications of nitrogen at 45- to 60-day intervals between spring and fall fertilizations. These applications should not exceed 1 pound of nitrogen per 1,000 square feet per application. .Occasionally, St. Augustine grass may need a supplemental application of nitrogen to enhance color during the summer. Use organic or slow-release nitrogen sources on lawns during the summer. Summer fertilization of St. Augustine grass growing in moderate shade should be avoided because of increased disease activity.
Fertilizers can be distributed with a broadcast (cyclone) or drop-type spreader. Uniform distribution is essential to prevent light and dark streaks across the lawn. For better distribution, divide the fertilizer to be applied into two equal lots. Apply one lot lengthwise and the other crosswise over the lawn (figure 2).
Type of Fertilizer
Choice of the type and grade of fertilizer material to use depends on soil test recommendations. Table 1 shows some analysis, ratios and equivalent applications rates of various fertilizers. In every fertilizer analysis (such as 12-4 8), the first number represents the percent nitrogen (N), the second number represents the percent phosphorus (P2O5) and the third number represents the percent potassium (K2O).
Additional nitrogen needed between the fall and spring applications for complete fertilizer can be supplied from one of several sources, as shown in table 2. Slowly available sources of nitrogen, such as ureaformaldehyde, IBDU, processed sewage sludge or cottonseed meal, are more desirable for summer applications of nitrogen than soluble sources such as ammonium nitrate, urea or ammonium sulfate. Slow-release and organic fertilizers usually cost more, but they are available to the grass over a longer period of time and help avoid the excessive growth produced by soluble nitrogen fertilizers. Soluble nitrogen sources should be applied in small amounts and more frequently than slowly soluble or slow-release types. Also, soluble nitrogen fertilizers are more likely to burn the grass than slow-release nitrogen fertilizers.