Saturday, May 18, 2002

Submitted by Calvin Finch, Ph.D., Manager, Conservation Division, Water Resources & Conservation Department, SAWS, and Horticulturist

A LITTLE “SIP” IS ALL YOU NEED FOR A GREEN LAWN

If you were not alert, you missed spring this year. We went from winter to summer over a period of a week. Temperatures in the low 90’s for a high and mid 70’s for a low are good growing conditions for a lawn, if the moisture is adequate. The best way to receive adequate moisture is with well-timed rains—weekly would be nice. Unfortunately, we rarely get rain when we need it for the lawn. That means if we want a green healthy lawn, irrigation is required. Irrigation can be wasteful or it can be efficient.

In my lawn all the winter grasses are just now dying and the Bermuda grass and St. Augustine are growing. We want to base any irrigation on the needs of the Bermuda and St. Augustine, not the dying rye, rescue or bluegrass. It does not matter how much water is applied to the cool weather weed grasses; they will not live when temperatures pass 85 degrees F.

The water needs of St. Augustine, zoysia, Bermuda, and buffalo grass in San Antonio have been scientifically determined over a five-year period by SAWS, the Texas Cooperative Extension, and the Bexar County Master Gardeners. They followed various watering schemes on the lawns of 64 area residents closely and then enlisted several thousand more folks to test the findings.

The results can be utilized in several manners. The best way is to select one day a week as your watering day and add back the amount of water used by the lawn that week by irrigating. These amounts are known because the water needed has a direct relationship with weather conditions. A weather station measures temperatures, humidity and solar radiation, and a computer translates that data into the amount of water that your St. Augustine grass needs that week. Last Saturday on the second page of the “SA Life” (where it appears every week), the water requirement for zoysia and St. Augustine in the sun was .5 inch; St. Augustine or zoysia in the shade also required .5 inch; Bermuda and buffalo grass did not need irrigation last week.

Using SIP (Seasonal Irrigation Program or Evapotranspiration [ET]) recommendations will require that you know how much water your sprinkler applies over a period of time. Take the time this weekend to make that determination. “Borrow” 4 or 5 pie pans from the pantry and place them on the lawn. Put one on the driest spot and one on the lushest spot with the rest in between. Run your sprinkler for 15 minutes and then stick a ruler in the pans to see how much water was applied. Average the amounts to make a rate determination for your sprinkler system.

One-quarter inch for 15 minutes is what many systems apply. If your average turned out to be .25 inch for 15 minutes, it would take a half-hour to apply .5 inch and 1 hour to apply 1 inch. Within a week these instructions will be available on the SAWS website saws.org. Obtain an ET (SIP) kit by calling the Texas Cooperative Extension at 467-6575 or SAWS at 704-7354 to find the distribution point closest to you.

On my irrigation control box there are three options for time settings for each station. That would mean if the SIP recommendation is .5 inch, option A can be run.

If your sprinkler control box does not allow you to have several settings for each station, you could delay irrigation for several days. If your timer is set for a length of time to apply .75 inch of water and the recommendation is only .5 inch, wait 3 extra days before irrigating.

The third way to use what was learned from the research project is to set your sprinkler system at the average/week rate for your type of lawn. St. Augustine and zoysia in the sun require an average of .75 inches of water per week in the summer to stay green. St. Augustine or zoysia in the shade and Bermuda in the sun require .50 inches of water through the summer; buffalo only requires about three-eighths of an inch. If you have a relatively deep (6 inches), heavy soil under your buffalo grass you can apply .75 inch every two weeks and meet its needs.

For those folks who do not have the recommended 4 inches of soil under the grass, you will be better off splitting the recommendation in half and applying the half ration twice per week. The shallow soil reservoir will only hold a small amount of water.

If you use SIP this year you will save money on individual water bills, do your part for San Antonio’s conservation effort, and still have green healthy grass.

If your neighborhood irrigates and is interested in following the SIP recommendations as a group, you will save 10 or more percent of your water for the year. Enroll the neighborhood in the Community Conservation Challenge as a group and the 10 percent water savings could translate into $1000 for a group project if you and 100 neighbors fulfill the commitment. Call Karen Guz at SAWS 704-7479 for the information. The Community Conservation Challenge is co-sponsored by SAWS and the Neighborhood Resource Center.