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LAWNS |
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KEY CONCEPTS
A. MowingB. Watering
1. When to water
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WATERING
Water is essential for plant growth. It is the liquid in each cell. Water carries nutrients and food throughout the plant. Water dissolves nutrients making it possible for the plant to absorb them. During Ohio summers, lawns that are not watered may go into dormancy. Summer days of high temperature, low humidity and breezes can quickly deplete available moisture.
There are many variables affecting how often a lawn may need to be watered. Gardeners must recognize signs of insufficient moisture. One visible sign is the change in color to a blue-green, purplish or smoky tinge. Another sign of need for water is footprints that leave an impression instead of bouncing right back.
Factors that influence how long a lawn can go between waterings (or rain) include the following:
! depth of roots;
! soil conditions;
! type of grass grown;
! weather conditions.
When the average daily temperature is above 60o F, the soil loses 1/4 inch of water each day. Turfgrasses in most Ohio soils will need 1 inch of water from rain or irrigation every 5 to 7 days.
Roots grow where there is water. A daily short sprinkling results in turfgrass with shallow roots. Deeply watered lawns have roots that grow deeply into the soil. Deep root systems have much more water to draw upon. Lawns with deep root systems can go much longer between waterings.
Lawns grown in sandy soil require more water and more frequent watering. Loam soils provide optimal conditions for holding water. Clay soils, although they hold more water, are more likely to have runoff if water is applied too heavily. Compacted soil will not absorb and hold much water.
Kentucky bluegrass and perennial ryegrass are not as drought tolerant as tall and fine fescues. Bluegrass and perennial ryegrass can be maintained with as little as an inch of water per week. In drier areas or where irrigation of the lawn is not possible, tall fescue may be a better option.
Ohio is prone to warm, windy summer days. These conditions result in the need for water. In some years, Ohio experiences long periods of summer drought.
Cool-season grasses go dormant and turn brown during prolonged droughts if not given supplemental water. Dormancy is the plant's way of coping with high temperatures and lack of moisture. Dormancy allows plants to remain alive until conditions change, while using minimal stored food.
Most healthy lawns can recover from dormancy without watering during the drought period. Gardeners can save money and effort by accepting brown turf during occasional dry spells. However, if the drought conditions last more than 4 to 6 weeks, the grass may die. Supplemental watering of 1/2 inch every 10 days during drought is advised to prevent the crowns of the grass from dehydrating. Drought damage is more severe when temperatures are high.
Many gardeners choose to maintain a green lawn during summer, despite droughts. Sufficient supplemental watering throughout the dry period is necessary to maintain active growth and green color.
Depth of watering is critical to lawn health. During summer a lawn usually requires 1 inch of water per week. One inch of water will wet most soils 6 to 8 inches deep. To determine the length of time needed to apply 1 inch of water, place several straight-sided containers 5 feet apart in a grid pattern throughout the area irrigated by the sprinkler.
Record the time it takes for water to collect to 1 inch in these containers. Use that length of time for supplemental watering. A quick but less accurate way to check the amount of water in soil is to poke a screwdriver into the ground. If it penetrates about 6 inches without much resistance, the lawn probably has been sufficiently watered.
When doing the straight-sided container test, also check that each container is filled with approximately the same amount of water. In-ground irrigation systems usually have a very even pattern of application. Some oscillating-arm sprinklers drop more water near the sprinkler than at the end of their range. Whirling-head sprinklers also deposit larger amounts of water close to the sprinkler. Each sprinkler may have variations in uniformity, so it is best to test them. When sprinklers give uneven application, it is important to overlap or supplement areas that receive less water.
With most sprinklers, it takes at least 1 hour to apply 1 inch of water. Heavy soils do not absorb water as quickly as lighter soils. If your soil is heavy clay, you may need to apply 1/2 inch at a time to avoid water runoff.
If lawn grasses do not receive deep waterings, they decrease in vigor. Frequent, brief watering causes shallow root development and, therefore, weak turf. Weak turf is apt to be invaded by weeds and insects and is less tolerant of water and heat stress.
The best time of day to water is morning through mid-afternoon. Light sprinkling by hand in the evening increases the chances of infection by diseases. Such watering practices promote ideal conditions for fungal diseases such as leaf spot. When water stays on grass blades for a long time, the probability of disease infection increases. Fungal diseases require moist conditions for their infection, growth and reproduction. Water applied late in the day may not have a chance to evaporate before nightfall.
MYTH: Watering in the middle of a hot, summer day will scald the lawn.
Grass blades are not burned by midday watering. If a lawn shows a need for supplemental watering, go ahead and irrigate. Grass plants use more water during the day because they are actively photosynthesizing. Watering cools grass that is heat stressed. However, afternoon watering does have its disadvantages:
! Evaporation is at its peak. This means that less of the water applied is actually available to the plant. It is estimated that up to 20% of the water applied evaporates from leaves and soil surface before it enters the ground.
! Water consumption is at its highest, possibly causing low water pressure.
MYTH: Daily watering will ensure that turf gets the moisture it needs to keep its green color.
The grass will get enough water to keep it green, but the roots will be shallow. If there is a watering ban, the shallow roots will not sustain the grass through a prolonged drought. It is better to apply 1 inch of water every 5 to 7 days.
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