Lawn Water Conservation
by Keith C. Hansen, Extension Horticulturist
Wouldn’t you know it! As I begin writing on water conservation, we get 3 inches of rain! This spring has blessed us with what appears to be drought-breaking rainfall. However, you can count on the fact that Texas weather is unpredictable. Occasional water shortages in Texas are a fact of life, and can dramatically affect our lives. Water rationing, crop failures, along with stressed or injured trees, shrubs and lawns, are all casualties of prolonged lack of rainfall.
The population of Texas is projected to increase significantly over the next 30 years, putting additional strains on our water resources. Although East Texas is a water-rich region of the State, droughts have resulted in water rationing in several East Texas communities in past years. Recent articles in the Tyler paper on the status of 2 proposed reservoirs in East Texas to supply the ever increasing population of the Metroplex underscore the critical situation the State faces regarding water. There is a need for continued vigilance for water conservation, practicing good landscape management to help buffer the impacts of any future droughts on both the health of plants in your yard and the region’s water resources.
Water utilities are required to implement drought contingency plans in the event of severe droughts. Outdoor watering is one of the first targets of water restrictions. You can do several things to condition your lawn and landscape to prepare for drought. Even if we do not experience another severe water shortage this year, summertime is traditionally a water-short period of the year when water consumption dramatically increases. So, it makes sense to prepare the yard for the eventuality of reduced rainfall.
Irrigation Practices. Since turf grass typically receives the largest amount of irrigation water, most water conservation practices focus on the lawn. Horticulturists and irrigation engineers agree that lawns and most landscape plants are over-watered, or watered inefficiently. Many people tend to rely on their automatic sprinkler systems to apply small amounts of water several times weekly to their lawn, regardless of any rainfall received. This practice is detrimental to the grass and actually promotes a lawn that requires more water and one that cannot withstand drought stress.
Less frequent, longer irrigations will help promote a deeper, more viable root system. Frequent (e.g., every other day), light waterings encourage shallow root systems that do not result in healthy turf. To develop a deep root system, lawns should only be watered when the first signs of wilt occur. Spots in the lawn that turn bluish-gray, footprints that remain in the grass, and many leaf blades folded in half length-wise are all indications that the lawn needs water.
Apply only enough water to wet the soil in the rootzone, at least 4 to 6 inches deep. A general recommendation is to apply approximately 1.0 inch of supplemental irrigation water per week in the spring and fall months when adequate rainfall does not occur. In the heat of summer, apply approximately 1.5 to 1.75 inches of supplemental irrigation per week if adequate rainfall does not occur. Note, St. Augustinegrass can actually survive on less than this amount of irrigation, but will not be as dense and green a stand of turfgrass.
Fertilization practices. Fertilization practices can enhance drought tolerance of turfgrasses if properly done. Understanding plant responses to nitrogen and potassium fertilization is helpful in developing a beneficial program as well as providing a well-balanced nutritional program.
All of the drought conditioning accomplished by proper irrigation and mowing practices can be eliminated by excessive nitrogen fertilization. Shoot growth is enhanced and root growth reduced by excessive nitrogen. Leaf blades become more lush as nitrogen fertilization increases. Drought conditioning can only be accomplished by applying just enough nitrogen to obtain a small but continuous amount of growth. Look for products with a high percentage of nitrogen in a slow release form.
Potassium fertilization can help turfgrasses increase their tolerance to many stresses, including drought. Potassium promotes increased root growth and thicker cell walls. Turfgrasses require potassium in nearly the same amount as nitrogen, especially in sandy soils where both can readily leach out. Soil test results from Smith County frequently show low to very low levels of potassium.
Soil pH is another important factor in plants ability to take up applied nutrients. Supplemental iron application can sometimes provide desirable green turf without promoting succulent shoot growth. Iron applications have also been shown to increase turfgrass rooting.
Too little nutrients can be just as stressful on grass as too much. Soil testing helps you monitor nutrient levels and determine turfgrass fertility and lime requirements.
Mowing. One of the most overlooked practices in maintaining a healthy lawn is mowing. Infrequently mowed lawns are more prone to stress, resulting in thinner turf and a weaker root system. The first key is to keep the blade sharp. A dull blade rips instead of cuts, resulting in ragged leaf edges which lose more water. Mowing height and frequency are crucial to a healthy lawn. Mow the lawn at the highest setting proper for your type of grass. Different grass types each have their own range of cutting height preferences.
Probably the most critical factor is mowing frequency. Remove no more than 1/3 of the length of the grass blade per mowing. Removing more than this places the grass under stress, reducing its ability to manufacture food to sustain growth. So, adjust your mowing frequency to keep pace with the growth of the lawn. In the summer, you might need to mow more than once a week, depending on the vigor of the lawn. In the cooler spring and fall, mowing will be less frequent. When you mow frequently, clippings should be returned to the lawn to recyle nutrients and organic matter back to soil.
The Extension publication “Lawn Water Management” is an excellent resource for more details on proper lawn watering.