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Soil Temperature, Root Growth, and Turf Quality during Heat Stress Conditions

Superintendents need to use every tool in their toolbox to maintain high quality turf during summer stress conditions. One of the critical factors in determining whether your turf can “take the heat” is having a strong turfgrass root system, which is discussed in this blog.

Good turf depends on a viable root system just like a tall building relies on a solid underpinning. The building may look great for awhile but sooner or later it will decline and collapse if it’s built on a poor foundation. For turfgrass to maintain good quality under summer stress conditions, it is critical to create optimal conditions for root development in the spring, and equally important to maintain that root mass as long as possible into the summer.

Research at major universities suggests that high soil temperature is more detrimental than high air temperature for growth in creeping bentgrass. The optimum temperature for root growth of cool-season grasses is 50 to 65 degrees F, which is often exceeded in summer. Root mortality of creeping bentgrass ranges from 40 to 60 percent during midsummer, which means about half of the roots produced prior to the summer die during the hot periods.

Waiting for visual indicators of your turf’s heat stress before taking action is not advised since at that stage, it may already be too late. As early as the 1970s researchers showed that shoots of turf suffering heat stress will continue to grow while roots do not. So, while the turf canopy may look OK, the turf’s underlying root foundation could be terribly weakened so that the next stress (heat, disease, foot/cart traffic, etc.) will cause the whole plant to collapse.

 Turf Screen reflects heat-producing infrared radiation, keeping the soil and plant 7°-12° F cooler

Extensive studies at Rutgers University and other research institutions clearly demonstrate that reducing soil temperature is an effective means to prevent summer bentgrass decline. There are many papers in the literature that suggest ways to reduce soil temperature (see links at the end of this blog); but with the invention of Turf Screen, superintendents now have another highly effective tool in their arsenal. Turf Screen reflects heat-producing infrared radiation, keeping the soil and plant 7°-12° F cooler, which can improve water use, reduce the incidence of heat stress, and enable basic physiological processes to continue in high temperatures when turfgrass would normally shut down.

For additional information on root development and maintenance, research results, and management techniques to reduce soil temperature, see the following links:

http://www.usga.org/course_care/regional_updates/regional_reports/northeast/Hold-On-To-Those-Roots—May-2012/

http://uwacadweb.uwyo.edu/eppl/Plant_Pathology/factsheets/sheets/Wy682r.pdf

http://grounds-mag.com/mag/grounds_maintenance_feeling_heat/

http://archive.lib.msu.edu/tic/mitgc/article/2000133.pdf