Evaluation of polymer-coated sands to conserve water

By Dr. Joey Young

Water is a precious resource around the world but when you live in a semiarid environment, water becomes a bit more precious. From residential landscapes to our athletic fields, it can be a challenge to manage turf under these environmental conditions. Many of our athletic fields in the West Texas region are artificial, and I believe one of the reasons may be the challenge of trying to provide safe and aesthetically pleasing fields during the season. With these challenges in mind, we have been establishing a number of research studies to evaluate newer bermudagrass cultivars for sports field use in this transition zone environment and develop techniques that can be used to save water and maintain acceptable turf quality.

A previous study nearing completion at Texas Tech evaluated numerous residential water conserving products applied to TifSport hybrid bermudagrass managed at 0.5 inch mowing height with and without core aerification. This study was designed to be a worst-case scenario by all means because after the initial product applications were made in mid-June, the irrigation was turned off completely until follow-up applications of some products needed to be made.

The study area received reasonable rainfall the first month of the trial through the first week of July; however, no more rain came until the middle of September. Under this significant water deficit stress situation, one of the products that successfully extended green cover compared to untreated control treatments was AquaSmart polymer-coated sand. In contrast to our hypothesis, data collected last year indicated that aerification before application of AquaSmart did not alter the effectiveness of the application. However, applying AquaSmart at a 4:1 ratio (sand:AquaSmart) provided significantly better color and green cover compared to untreated control treatments for 4-5 weeks with no irrigation or rainfall.

Some of the biggest benefits to this application for a sports field manager are the extended life of the product in the soil and the potential to apply a mixture of polymer-coated sand in your typical topdressing practices. A single application of mix was applied in mid-June last year and incorporated into the canopy using brooms for our small plot work. The abrasive actions of getting the sand into the canopy resulted in poor visual turf quality, color, and green cover for 1-2 weeks after application, but darker green color was evident following recovery in 2-3 weeks after application. No other applications were made throughout the year, but the significance of drought stress with no irrigation or rain in July and August resulted in a sharp decline in turf quality, color, and green cover that remained statistically similar to untreated control treatments for the remainder of the study.

Following the first year of data collection, we believe the polymer-coated sands residing around the crown of the plant (aerified or non-aerified) provided greater hydration to the growing point helping maintain color for a longer period than untreated control treatments. Ultimately, soil moisture levels at 1.5 and 3-inch depths were never significantly different with any of our treatments, meaning something other than available soil moisture had to be providing the visual benefits observed. We are conducting this same research again this year and look to publish results from the study early next year.

Other studies

The success and preliminary conclusions of this first research trial led to other ideas we wanted to evaluate. As previously mentioned, there are numerous artificial athletic fields throughout the Panhandle of Texas. I believe one of the reasons for this is the challenge associated with growing bermudagrasses in this short-seasoned transition zone area. The cold and frost can come early and also surprise us with a late freeze well into the spring season resulting in a meager growing season. Bermudagrass needs and prefers a long growing period before resting during the winter months, so we wanted to try and establish some of the newest bermudagrass cultivars that have been demonstrated to be effective sports turf selections in other transition zone areas within the US.

We recently obtained and are establishing five bermudagrass cultivars: Tifway 419, Celebration, Riviera (seeded), NorthBridge, and Latitude 36. We will also be establishing the University of Georgia’s newest release, TifTuf, next spring in the area. In addition to evaluating these grasses post-establishment, we were awarded funding from Texas A&M to evaluate the use of AquaSmart as a potential method to reduce irrigation requirements to establish sprigs or seeded bermudagrass.

We established the grasses under three irrigation zones to provide different levels of water. Control irrigation runs for 15 minutes two times per day 7 days per week; moderate irrigation runs 20 minutes one time per day 6 days per week, and the lowest irrigation runs for 15 minutes 4 days per week. After placing sprigs and seed of the various bermudagrass cultivars in the area, AquaSmart was applied to strips of the grass at 0, 40, or 80 lbs./1,000 square feet using a 3-foot drop spreader. The fine particle size of the polymer-coated sand being dry at application makes the direct application of the product through a drop spreader very simple and effective.

This trial was established at two separate planting dates, the first week of July and the first week of August last summer. AquaSmart treatments were applied the day of sprigging or seeding along with a heavy topdressing of USGA specification sand to cover sprigs and seed to prevent desiccation. Irrigation treatments were initiated following sand topdressing and remain in place since sprigging. There was no rainfall following the first planting date, but we had lots of trouble with weed infestation in the initial planting area that made rating the growth of sprigs and seed difficult.

The seeded variety grew in very well and is currently 100% covered with grass at the two higher irrigation levels, but the lowest irrigation level still lacks full cover of grass. The sprigged plots are growing in effectively; however, they will require much more growth to completely fill the area. It is difficult to determine if the AquaSmart treatments are providing benefits to establish the turf more quickly with reduced irrigation, but hopefully the weed pressure will be managed more effectively with our second planting date to more effectively evaluate the potential benefits.

An application of pre-emerge herbicide (oxidiazon) to non-seeded plots will hopefully limit weed pressure and provide improved data collection. As of 2 weeks post planting, there was limited evidence of turf growth from the second planting date, but we should start seeing some new growth very soon from these treatments.

The ultimate goal and potential benefit of this research would be to determine if the polymer-coated sands could maintain improved moisture around sprigs or seeded bermudagrasses to reduce the irrigation requirements to establish grasses on an athletic field. Turf researchers have successfully demonstrated effective management practices and products that can reduce the water requirements of established turf species and cultivars; however, limited research has proven effective techniques to reduce water requirements when establishing turf. If this product can effectively reduce water needs at establishment, this could be a major breakthrough for sports field managers undergoing renovations or overseeding practices in the spring.

There are a number of companies that provided products for us to conduct this research that should be acknowledged. RainBird provided new irrigation valves, heads, and a controller for us to alter the irrigation system into three independent zones. Sod Solutions provided sod that was cut into sprigs, and Johnston Seed Company provide Riviera bermudagrass. AquaSmart donated a large quantity of their product and additional financial support was provided through Texas A&M’s Turf Research, Education, and Extension Endowment.

Joseph Young, PhD, is an assistant professor in the Department of Plant and Soil Sciences, Texas Tech University. Joey also serves as the Technical Editor for this magazine. He can be reached at joey.young@ttu.edu.