Shade Tolerance of ‘Diamond' ZOYSIAGRASS Managed UNDER Putting GREEN CONDITIONS with the USE of Trinexapac-Ethyl.

Shade or low light tolerance is an increasingly important issue to turf managers as they are often expected to grow turf in less than ideal agronomic conditions.  As permanent structures such as residential buildings add to already problematic shade caused by trees, and other barriers, new solutions are needed to help turf managers provide acceptable turf conditions.  The plant growth regulator, Trinexapac-ethyl (or TE), can lessen negative responses of turfgrass to shade.  The purpose of this research was to determine the shade tolerance of ‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.] when maintained under putting green conditions with and without the use of Trinexapac-ethyl.

The study included three levels of shade: none, low, and high (0%, 60%, and 90%).  The three levels of shade were applied continuously to all plots using a neutral density, poly-fiber black shade cloth.  Two treatments were within each level of shade.  One included the application of Trinexapac-ethyl with a CO₂ backpack sprayer at a rate of 0.57 kg ai ha^-1wk^-1 (1.5 oz/ 1000 ft² wk^-1) operating at 20 GPA with an 8003 flat flan nozzle and without Trinexapac-ethyl application.  Application of shade was initiated on 23 May 2008 and removed 30 October 2008.  In 2009 application of shade was initiated 24 May and removed 31 October.  Plot size was 2m by 1.5m maintained at a height of 45cm above ground level to maintain proper airflow.   Shade tents were removed 2 hours weekly to take measurements and perform maintenance. 

            Application of Trinexapac-ethyl to 90% shade increased turf quality by ~4 units from 1 to ~5 at the end of each study year.  While still not commercially acceptable (TQ≥7), some turf cover was still preserved.  Other plant responses measured included percent lateral regrowth (LR), total shoot chlorophyll, clipping yield, ball roll distance, and total non-structural carbohydrates (TNC).