Tech Notes Issue 5

Mowing Height Adjustment Important on Shaded Greens

Managing ultradwarf couch or creeping bentgrass greens under golf course conditions is a challenge. Managing these same greens in shade is difficult and often frustrating.

Shade not only influences the amount of light available for plant photosynthesis but also affect light quality. The reduction in light along with changes in quality (excess in far-red light and a deficiency in red light) cause turfgrass plants to produce thin, delicate leaves and rapid, vertical shoot growth (5). These plants are more succulent and commonly have poor root systems compared to plants in full sun (3).

Maintaining plant energy
Shade reduces the turfgrass plants energy needed for growth, development, and  reproduction. To increase photosynthesis on shaded greens there are three options. The first is to cut the trees down exposing the greens to direct sunlight. This is rarely popular with golfers. A second option is to thin the tree canopies, but this procedure is likely to have little impact. Research suggests that shade duration is more important than shade density (2).

The third option is to raise the height of cut on shaded greens. Raising the height on creeping bentgrass greens from 3.2 mm to 3.6 mm will increase leaf area by 13 percent and increase the photosynthetic potential by 13 percent. Increasing the height to 3.99 mm in creates 25 percent more photosynthetic potential (1).

In studies on 'Champion' and 'Tifeagle' ultradwarf couch increasing the height from 3.2 mm to 3.9 mm  increased the density of the turf in both full sun and 30 percent shade. The net photosynthetic rate increased 13 and 10 percent for the turf grown in full sun and 30 percent shade, respectively (4).

References:
1. Bell, G. and K. Danneberger. 1999. Managing creeping bentgrass in shade. Golf Course Management 67(10):56-60.
2. Bell, G.E. and T.K. Danneberger. 1999. Temproal shade on creeping bentgrass turf. Crop Science 39:1142-1146.
3. Dudeck, A.E. and C.H. Peacock. 1992. Shade and turfgrass culture. In Turfgrass. American Society of Agronomy, Madison, WI.
4. Miller, G.L. and J.T. Edenfield. 2002. Light intensity and duration influence growth of ultradwarf bermudagrass. Golf Course Management 70(9): 111-113.
5. Smith, H., J.J. Casal, and G.M. Jacson. 1990. Reflection signals and the perception by phytochrome of the proximity of neighboring vegetation. Plant Cell Environment 13:73-78