New Waves November 2011

Breaking news about water resources research and education in Texas

Tools offered to determine how much is enough when watering the grass

Tools offered to determine how much is enough when watering the grass Watering grass, whether in a park, a football field or a homeowner’s yard, was an issue throughout the summer as those responsible for upkeep tried to keep things green under drought conditions.

But pouring water onto grass during periods of drought is not necessary and can even have the opposite effect of what lawn managers might want, according to Texas AgriLife Extension Service experts.

Dr. Jim McAfee, AgriLife Extension turfgrass specialist in Dallas, and Dr. David Chalmers, AgriLife Extension state turfgrass specialist in College Station, say two things are needed for anyone to maximize the effectiveness of the water they put on grass—sprinkler auditing and evapotranspiration information.

The goal this summer was to not lose the grass, Chalmers said. To accomplish that, consumers need research-based information on the minimum amount of irrigation required to maintain the viability of warm-season turfgrass, regardless of the appearance, through long-term drought.

Chalmers conducted a three-month study this summer looking at deficit turf irrigation on St. Augustine grass based upon weather station evapotranspiration data. The study indicated that even at levels of 24 percent of the evapotranspiration rate, which is considered very high stress, and 36 percent or normal stress, the ground cover will be greatly reduced but the plant population would be maintained for regrowth and lawn recovery when more moisture is available.

The amount of irrigation needed to maintain warm-season turf with acceptable quality was equal to 60 percent of weather station evapotranspiration, Chalmers said.

Evapotranspiration for some areas can be found by going to and clicking on the county and weather station nearest to the lawn. It will calculate how much water needs to be applied with input of a little information, McAfee said. This site does not cover the entire state, so others may need to find an alternative source for collecting the evapotranspiration rate.

“In addition to knowing how much evapotranspiration is taking place, you have to know what your system is putting out,” he said.

So one of the first steps to correctly and efficiently water grass is auditing the sprinkler system in use, McAfee said.

“In some cases, reducing the amount of water these people are putting on their sports fields can actually improve the field,” he said. “The whole thing is about having available oxygen to the roots. Overwatering can reduce the quality of the field, because the roots can’t get oxygen when they are water-logged.”

Read the entire AgriLife TODAY story for more information.

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