Dry conditions often persist in most parts of Louisiana this time of year and into the summer, but LSU AgCenter horticulturist Dr. Tom Koske says there are actions you can take to avoid the lawn problems associated with drought.
"There are some things to keep in mind in the short term to avoid drought problems with turf grasses," Koske says, adding that those are to maximize the efficiency of your irrigation water and to carefully manage the stress your grass is facing.
"You need to make the most of your water by irrigating in the early morning, if at all possible," Koske advises, explaining, "This limits the duration of leaf surface moisture – a contributor to disease development. It also assures a better distribution of the irrigation water, since wind likely will be low to nonexistent, and it reduces moisture losses because of evaporation."
The LSU AgCenter expert says municipal water pressure generally is best in the morning, as well, which offers another benefit to morning irrigation.
When you do irrigate, Koske says to water so that the root zone is moistened to several inches rather than putting out a little water every day.
"Light daily irrigations will cause roots to accumulate in the top inch of soil," he explains. "This restricts the roots and sets up a dangerous situation for the turf."
Heavier clay soils hold and require more water than do sandy loams, according to Koske, who says they should be watered longer but less frequently.
"These heavier soils usually require watering in ‘cycles,’" he says, explaining, "A cycle should be ended when surface water begins to run off into the street, for example. Then wait a while and water again."
The horticulturist says to check with a shovel to determine how far down the moisture has penetrated, and continue such watering cycles until the moist zone is at least 3 inches to 4 inches deep. Make notes about the length and number of cycles it took. Then move your sprinkler and start over on another area.
As for determining how often you’ll need to water, Koske says to go back to the well- watered area and push a screw driver into the soil several inches.
"Note the force needed. As the soil dries, it gets harder to push through," he explains. "The amount of resistance to penetration can give you an idea of how dry the soil has become and can help you to schedule the next irrigation cycle."
Turning to the issue of managing the stress your grass is facing, Koske says even the hardiest ones can face problems.
"Your grass will be under serious stress because of dry environmental conditions. Even our warm-season grasses that are adapted to hot, dry conditions can show the wear and tear of the summertime heat and a lack of rainfall," he says. "If your turf isn't being irrigated and it has been dry, it is very likely to be suffering from a lack of moisture. It may be hanging on, waiting for rain, or it may have entered a dormant state waiting for the rain."
The LSU AgCenter horticulturist says there are serious concerns for loss of centipedegrass stands during an extended drought, but most bermudagrasses and St. Augustine will bounce back when a significant rainfall – a half-inch or more – is received.
Koske also says that as we ride out these weather conditions, you should keep in mind many standard cultural and chemical practices must be altered because of the stress the grass is under.
"Pesticides should be applied only with assurances that the desirable turf can withstand the treatment," Koske says, adding, "Plus, if the pests are not active, there is no reason to apply the pesticide in the first place."
In one case he cites, however, Koske notes that chinchbugs often are more active in hot, dry conditions.
Another common problem seen recently is with post-emergence grass and nutsedge herbicide applications that have been relatively ineffective. According to Koske, this stems primarily from limited uptake and translocation of the chemical by the targeted weeds because the weeds also are suffering from drought stress. He advises postponing most weed control efforts until drought conditions subside.
The LSU AgCenter horticulturist says the same concepts apply for fertilization.
"If you have ample irrigation, your warm-season grasses will continue to respond to nitrogen applications," he says. "However, there is no point in fertilizing grasses under moisture stress that cannot be irrigated sufficiently to support active growth. Under these conditions, the plant is basically inactive, and the fertilizer is unavailable since water is the carrier of the nutrient, so about the only thing you are doing is increasing the salt content of the soil."