Barrett A. Courville | 5/20/2011 9:11:13 PM
For the second consecutive year we are experiencing a significant drought here in south Louisiana. Many homeowners don’t know the proper method of lawn irrigation. Today I will try to cover some important information on proper lawn irrigation. Here in south La. we generally have more rain then we need and irrigation is usually only required every now and then. Usually June, July, August and September are our driest months. More water is used during the summer months by grass than is replaced by rainfall. If supplemental irrigation is not added, some turf grasses have mechanisms to survive the dry period. Warm-season grasses like centipede grass, bermuda grass, zoysia grass and St. Augustine grass will survive dry periods and will rebound when favorable conditions return. During dormancy the plants stop growth of leaves and shoots, causing the existing turf to turn brown. The plants usually do not die, although the leaves cease growing. When adequate water returns, new growth will occur with no long-term damage.
There are exceptions when it is important to keep the grass growing throughout the summer by supplemental irrigation. Any turf that is affected by or is recovering from pest damage, such as disease, insects or excessive weed growth, should receive plenty of water to aid recovery. Any area that has been recently seeded should be watered frequently.
How much water should I use?
The amount of water to apply depends on the soil type and the wetness of the soil. The preferable method is to thoroughly wet the soil down to a depth of 5 inches. If the soil is initially very dry, it may take 1/2 inch of water to wet a sandy soil down to a depth of 5 inches, while 1-1/2 inches of water may be needed to wet a clay soil down that far. Once the soil is thoroughly wet to a depth of 5 inches, any additional water will simply drain below the root zone. Occasional extraction of soil cores after normal irrigation can help give some idea of how deeply you are watering. Another easy method is to sink a shovel into the soil and spread the hole so you can see how far the water has penetrated. Then remove the shovel and press the soil into place with your foot.
Several aspects of lawn sprinkling are important. First, determine how uniform and how much water is applied in a normal irrigation. This can be done by placing a row of equal-sized, straight-sided cans in a line at one or two foot intervals from the sprinkler and out to the farthest point of watering. Following a normal sprinkling of known time, measure the amount of water collected in each can. Then determine the appropriate placement of sprinklers and length of time to water for a uniform distribution of the desired amount of water.
Second, remember that water should not be allowed to run off the surface or to form puddles because these lead to poor distribution and efficiency of water. Occasionally, the rate at which water can enter the soil is less than the amount applied by the sprinkler after watering has continued for a time. If you notice water running off the surface or forming puddles but you still want to apply more water, turn the water off for 15 minutes, then resume watering until the desired amount has been added.
How often should I water?
This is not an easy question to answer because frequency will be affected by grass species, soil texture, climate, exposure and intensity of use. Ideally, the grass plants should dictate the watering program. Slight wilting, a color change to a more grayish or bluish-green shade or foot printing (when plants will not rebound after walking on them) are indications that irrigation is necessary.
It is desirable to keep the interval between watering as long as possible without allowing the plants to go into water stress. Deep, infrequent irrigations cause plants to develop deep, strong root systems that can extract water from a much larger volume of soil than the shallow roots associated with light, frequent irrigations.
Some areas of the lawn will probably dry faster than the rest. This is common on southern exposures, sunny areas, borders of sidewalks and slopes. Hand watering of these areas may save water by extending the interval between watering of the entire lawn.
When should I water?
The most efficient time to water lawns is probably early in the morning hours from 4 a.m. to 8 a.m. - less water is lost to evaporation due to lower temperatures and less sunlight. Also, wind velocities are usually lower than they will be later in the day, so distribution is improved. Water demand on municipal systems is usually less at that time as well.
Midday watering, though good for the plants since it cools the plant temperatures and reduces heat stress, is not as efficient because some of the water evaporates before getting into the soil.
Watering in the evening should be avoided. If the grass plants go into the nighttime hours wet, they will remain wet for extended periods of time. This may favor the growth and development of turf grass diseases.
Lawn Watering Tips