News Article for June 22, 2009 from LSU AgCenter County Agent Kenny Sharpe:
Lack of rain fall and very high temperatures are starting to take a toll. Pastures are drying up, irrigation is more frequent in the commercial vegetables, and home lawns and gardens are burning up. Not to mention that so many people are trying to water their lawns in the afternoon that there is hardly enough water pressure in the shower to knock the soap off of you.
Earlier in the spring we were getting adequate rains, but now most of the lawns in my neighborhood are turning brown, especially near the trees. Many of the lawns were just now recovering from winter and starting to look nice, so if you allow a lot of damage from drought stress, you will have a problem recovering before winter.
I have a lot of conversations with people about when to water. The best time to water from an efficiency standpoint is morning. If you have an irrigation system, then it is usually set for predawn to take advantage of good pressure before everyone wakes up and starts using household water. If you are watering by hand or sprinklers, then you do not have to get up that early. I would recommend, however, that you to water in the morning to reduce evaporation and to reduce plant diseases.
Many people in my neighborhood come in from work and turn the sprinklers on or they will wait until late afternoon when the sun goes down. If the grass or ornamental plants are wet at night, you have a great potential for plant diseases to be rampant. If you get a fungal disease, it will actively spread all night in the moisture and will actually make your lawn look worse.
The rule to irrigation is to never put the plants to bed wet. In other words, if at all possible, irrigate so that the sun will dry the plants' foliage before nightfall. Yes, you can irrigate in the middle of the day as long as you do not let the water puddle, since standing water will scald the plants. You will, however, get more evaporation loss by watering in the middle of the day.
The other question is how often do I water? The answer depends on several site-specific criteria, but it is always best to water thoroughly once a week than lightly several times a week or daily. You want to water slowly and deeply to encourage deep root penetration, which makes your lawn grasses more drought resistant. If you water lightly you encourage the roots to grow toward the surface to get moisture and this shallow soil zone is much hotter and much more prone to drought. .
Pay attention to water runoff. These clay soils will only take between a ¼ and ½ inch of water at a time before running off into the street or ditch. When the soil has absorbed all that it can at one time, turn off the water for a while and then add more water later.
To really tell how good you are doing, you can dig a hole in the corner of the lawn down about 4 inches deep and check for water penetration. Once you get the soil wet down that deep, you may be able to go a couple of weeks without irrigation even in the absence of rain.
As a general rule it will take 1-2 inches of rain a week to keep up with evaporation and the plants' water requirements. A rain gauge is a useful tool to help you keep up with how much water has fallen so you can decide when to water and how much. It also helps if you put a container in the lawn when watering to measure how much water you are applying.
For more information on this or related topics, contact Kenny at 225-686-3020.