Irrigating the Lawn

This article originally ran in the Ruston Daily Leader on May 25th, 2010.

Since the irrigation of lawns and other ornamental plantings can use as much as 50 percent of a community’s water supply during the summer months, water restrictions are becoming commonplace throughout the country.

Improper irrigation practices may be more harmful to lawns than not irrigation at all. For example, light or occasional irrigation during extreme drought may cause the depletion of stored carbohydrates, reducing the vigor and drought tolerance of the lawn. If this situation occurs and irrigation cannot be maintained properly, it may be advisable to allow the turf to go dormant. This is the natural defense mechanism of the plant. After the drought, the lawn grass will usually return to normal growth. The decision whether or not to irrigate depends on the use of the area, the desired aesthetic look, the severity of the drought, the availability of water, and your budget. Under less severe situations, improper irrigation can increase both disease and weeds and can produce a meager, shallow root system.

Recognizing Drought Stress
The first visual symptom of a drought stressed lawn is often a loss of rigidity that is evident by “footprints”, which is the appearance of footprints on the lawn after walking over it. If the lawn is under water stress, footprints will be highly visible because of the shoots’ inability to spring back. Lawns that are well-watered will barely show the foot printing effect, springing back almost immediately. Other symptoms of water stress include a blue-green or gray leaf color and finally if stress continues, the tops begin to turn brown and die. Storage of water in the roots and crowns will keep the plant alive long after the shoots die.

Ideally, the lawn should be watered before any of these symptoms appear. If water is applied during the wilting stage, the grass will usually recover rapidly. However, lawns that turn brown and enter the dormant stage take considerable time to come back to a restored, healthy condition.

Frequency and Amount of Irrigation
As previously mentioned, to maintain a lawns’ vigor and quality, it is ideal to start irrigating before visual symptoms are apparent. As a rule, daily irrigation is not recommended for mature stands of lawns. Such a practice keeps the soil surface constantly wet and encourages shallow rooting. With the majority of the roots in the surface layer of the soil, the lawn becomes more susceptible to stress during even short periods of drought. Light, frequent irrigations are only recommended for newly seeded or vegetative propagated areas.

To develop a deep, extensive root system, irrigate deeply but infrequently. Deep, infrequent irrigation will allow the surface to dry out, forcing roots to grow into the lower depths of the soil that contain water. Generally, on our sandy soils in northern Louisiana water may be applied at the rate of one inch every 3 to 4 days. If more than one inch is applied at one irrigation, much of it may move down below the root system and be wasted.

The amount of water applied can be determined with a rain gauge or the coffee or tuna can approach. After running your irrigation system and measuring the water in the cans to determine if one inch has been applied.

Time of Day to Irrigate
Technically, lawns can be irrigated any time of day or night. However, depending on the situation, certain times of the day may be more advantageous than others. For instance, at night less water is loss to evaporation because of reduced wind movement, cooler temperature, and higher humidity. One serious draw back of night irrigation is that disease activity may increase on lawns watered at night.

Midday or mid-afternoon irrigation has its own advantages and disadvantages. First, as much as 50 percent of the water applied may be lost to evaporation before it hits the ground. Disease activity resulting from free-standing water is greatly reduced, but if the water application rate exceeds the infiltration rate or if drainage is poor, the turf may be subject to scald. Scald is the scorched appearance of the lawn that has been submerged or partially submerged on bright, sunny days, when water temperature increases to a point that injures the plant tissue.

Early morning irrigation combines several advantages of night and midday watering. For example, winds are reduced, humidity is high, and solar radiation is low. These factors help to reduce evaporation. Early or mid-morning irrigation also avoids prolonged free water on the lawn, discouraging disease development. Reduced wind movement allows proper water distribution from the sprinkler. There is also less chance of interfering with the use of the area.

Please contact me if you have any questions regarding this article or any other related topics.
5/24/2010 11:13:42 PM
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