December 2011 Articles

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Proper watering is important during dry weather

Proper watering is important during dry weather By Dan Gill, LSU AgCenter Horticulturist
Dry weather has been common around the state since spring started, and most of us have received less than the typical amount of rain this year. We don’t know how much rain will fall this summer, but we can be fairly certain that there will be at least some periods of hot, dry weather when we will need to water our landscapes.
How often we need to water varies, depending on such factors as temperature, rainfall, humidity, season, plants and light intensity. You need to irrigate more frequently, for instance, when temperatures are high, plants are growing in full sun and a lot of plants compete for the water in the soil – when a tree is nearby, for instance, or in a thickly planted bed). Proper watering is a function of applying the right amount of water at the appropriate times.
Many gardeners tend to water lightly every day during dry weather, but the water doesn’t penetrate deeply into the soil. Because roots only grow where there is adequate moisture, this results in a shallow root system. Shallow-rooted plants are unable to tap reserves of water deeper in the soil and are prone to drought stress in even brief dry periods. Eventually, your plants become dependent on you to water them constantly. And watering every day also increases the chances of foliar diseases and root or crown rots.
As relaxing as hand watering is to the gardener, it is not an effective way to irrigate plants growing in the ground. When we water by hand, we tend to apply water rapidly for a short period and move on. Applied this way, water does not penetrate deeply into the soil. To irrigate properly, water needs to be applied slowly over a sufficient period of time to allow it to soak deeply into the soil.
To irrigate thoroughly, enough water should be applied to penetrate about 6 inches into the soil. Applying about an inch of water to medium-textured soils generally will accomplish this. A thorough watering should not be necessary for established landscape plants more often than once a week.
Early morning is the preferred time to irrigate. This provides plants adequate moisture going into the hottest time of the day when they need it most. And sunlight helps the foliage to dry rapidly, reducing the possibility of foliar disease problems. (Wetting the plants while the sun is shining on them will not burn the leaves.) If sprinklers are used, watering in the early morning when it is cooler and humidity is high reduces water lost to evaporation.
You can use a variety of methods to irrigate your landscape. You may even use different methods in different areas.
Soaker hoses are made of a material that oozes water slowly. They apply water very efficiently, don’t wet the foliage – reducing potential disease problems – and can be left in place or moved easily. Soaker hoses must be laid fairly close to the plants to be effective, so snake them throughout a bed around the plants. It may be helpful to pin the soaker hose in place with U-shaped pieces of wire to make it stay where you want it. Finally, cover soaker hoses with mulch so they are not noticeable. Soaker hoses are ideal for irrigating flower beds, vegetable gardens and shrub plantings.
The most common and popular method of landscape irrigation is sprinklers, which are also the only practical way to water lawns and large trees. Installed underground systems and hose-end sprinklers are the two basic types.
Underground systems are effective and very convenient, but they’re expensive to purchase and generally must be installed professionally. Professional landscape irrigation system installers must be licensed by the Louisiana Department of Agriculture and Forestry. Ask to see a copy of their license to make sure the company or individual that installs your system is reputable and knows what they are doing.
Most home gardeners use hose-end sprinklers. They are less expensive and do not require professional instillation. But they’re inconvenient to use because they must be moved to cover large areas and generally must be picked up after use.
To figure out how long to leave your sprinkler on to apply one inch of water, first, place several empty cans in the spray pattern of the sprinkler. Turn on the sprinkler and check the time. When about an inch of water has accumulated in most of the cans, check the time again. That’s how long it takes your sprinkler to apply an inch of water – and about how long you should leave it on to thoroughly irrigate an area.
The best check of how thoroughly an area has been watered is to go back about 15 minutes after watering and dig into the soil with a trowel. Did the water penetrate 6 to 8 inches? Check several places. This procedure also works to calibrate an installed irrigation system or hose-end sprinklers.
In some situations, such as on slopes and heavy clay soils, the water may need to be added even more slowly to reduce runoff. It takes water longer to penetrate heavy clay soils than light sandy soils. Run the sprinkler on for 10 to 15 minutes and off for 15 to 20 minutes until you’ve applied an inch of water.
Finally, don’t forget to keep your landscape beds and vegetable gardens well mulched. A layer of mulch covering the soil surface cuts down on evaporation, conserves soil moistures and reduces watering frequency.