Prepare your lawn for drought and save our valuable water resources every day
You may have noticed that your lawn is drying out much faster these last few weeks.
April is a very dry month averaging only 2.03 inches of potential rain fall. Add to that fact the higher temperatures and wind and you end up with a high evapotranspiration rate.
Evapotranspiration (ET) is a process by which water is transferred to the atmosphere from vegetative surfaces. ET consists of two components, evaporation and transpiration. Evaporation is a physical process by which water is changed from a liquid to a gaseous state. Evaporation takes place from free water surfaces such as ponds, streams, wet soils or wet vegetation. Transpiration, the other component of ET, is a plant process of water loss. For practical purposes it is impossible to separate the evaporation and transpiration components of water loss from turf surfaces. That is why the term evapotranspiration is used.
The amount of water transferred into the atmosphere by evapotranspiration from turf surfaces is governed by a number of environmental factors. Sunlight, relative humidity, temperature, wind and available soil moisture supply are the controlling elements. Minimal ET rates occur when there are dark, cloudy days with high relative humidity, low temperatures and no wind. Maximum ET rates occur on bright sunny days with low relative humidity, high temperatures, and moderate to high winds. This means higher irrigation requirements than were needed during the previous cooler months.
The idea when watering is to wet the entire root zone but don’t saturate the soil. A general rule is to apply from three-fourths to one inch of water every two weeks in cooler, winter months and one to two times per week in hot spring and summer months. All soils are not the same so you should adjust the amount of water to apply to your particular lawn.
Knowing the amount of water your sprinkler system applies to your lawn is an important step in using water efficiently. Most people irrigate for a given number of minutes without knowing how much water they are really applying.
Calibrating or determining the rate of water your sprinkler system applies is an easy job.
1. Obtain five to ten coffee cans, tuna fish cans or other straight sided containers to catch the irrigation water. Containers three to six inches in diameter work best.
2. Place the containers in one zone at a time. Scatter the cans at random within the zone. Repeat the entire procedure in every zone because there may be differences in the irrigation rates.
3. Turn the water on for fifteen minutes.
4. Use a ruler to measure the depth of water in each container. The more precise the measurement, the better your calibration will be. Measurements to the nearest eighth of an inch are adequate.
5. Find the average depth of water collected in the containers by adding the depths and then divide by the number of containers.
6. To determine the irrigation rate in inches per hour multiply the average depth of water times four.
Try to calibrate the system during the same time the system is normally run so that water pressures are similar. Low water pressure can significantly reduce the amount and coverage of water applied by a sprinkler system. Never apply more than one inch of water per irrigation. Avoid mixing sprinkler head types. Mist heads apply more water than stream and rotor heads. Match sprinkler heads for uniform coverage. Check your system frequently. Replace broken heads, clear clogged nozzles and adjust the direction of spray. Now that you know your sprinkler system irrigation rate, you can more efficiently apply water to your lawn.
Avoid extremes in water. Light, frequent waterings are inefficient and produce shallow root systems. Excessive irrigation which keeps the roots saturated with water is also harmful to the grass. Roots need air to function and too much water kills or greatly decreases root growth.
Proper mowing practices are also essential for a drought prepared turf. Every time a lawn is mowed the grass is stressed which reduces root growth. Mowing frequency and height of cut should be carefully considered. Use the highest setting on the mower as a short cut will stress the turf. By increasing the grass leaf area, more photosynthesis can occur. This means more carbohydrates for plant growth, especially root growth. The higher the height of cut on a lawn the deeper and more extensive the root system will be. Adjust the frequency of mowing to the growth of the turf. At least once a week in summer, while once a month may be enough in the winter. Also, keep the mower blades sharp. A clean cut leaf blade will heal more quickly and thus lose less water than a shredded blade.
Fertilization practices can enhance drought tolerance of turfgrass if properly done. All the drought conditioning accomplished by proper irrigation and mowing practices may be eliminated by excessive nitrogen fertilization. Shoot growth is enhanced and root growth reduced by excessive nitrogen. Drought conditioning can only be accomplished by applying just enough nitrogen to obtain a small but continuous amount of growth. Lawns should never be fertilized to deepen the green color since southern turf grasses are more often yellow-green. Potassium fertilization promotes increased root growth and thicker cell walls. Drought tolerance is improved by applying potassium. Turf grasses require potassium in nearly the same amount as nitrogen, especially in sandy soils where both can readily leach out. In times of drought a 15-0-15 lawn fertilizer would be preferable over a 16-0-8 analysis.
Pest control on lawns should be done with great care because pesticides can add extra stress through phytotoxicity (chemical damage to plants). Pesticides should never be applied on a preventative basis. When a pest problem is diagnosed however, it should be treated appropriately. Spot treatments can be as effective as treating the whole lawn. Be particularly watchful for insects and diseases which attack turf grass root systems such as grubs or root rots.
If you have areas in your lawn which will not survive without extraordinary care, alternatives to turf should be considered. Mulched beds, shrubs and ground covers which do not require supplemental irrigation should be chosen.
Don’t wait for water restrictions to be imposed. Prepare your lawn for drought and save our valuable water resources every day of the year.
Eileen Ward and her husband Peter have owned and operated Greensward of Marco, Inc., a lawn maintenance and landscaping company, since 1981.