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1996, No. 6
TURF WATER USE RATES AND IRRIGATION MANAGEMENT
Sustaining high-quality turf during normal spring and summer weather usually tests the abilities of Illinois turfgrass managers.
This growing season is no exception.
The cool, wet spring of 1996 has given way to summer.
While statewide temperatures have become more seasonal, precipitation has been spotty; some areas of the state are very dry, while other areas have received adequate moisture.
Throughout these periods of variable water availability, managing turfgrass irrigation is important for maintaining healthy, actively growing turf.
Consideration of the turf Water Use Rate (WUR) can assist turf managers in making irrigation decisions.
The turfgrass WUR is measured in inches of water used per day and combines the quantities of water used for turf growth, the water transpired from the turf plants, and the water that evaporates from the associated soils.
During normal growing conditions, the WUR is approximately 0.1 to 0.3 inch of water per day.
This amount can increase to as high as 0.45 inch of water per day under conditions of maximum WUR.
How do environmental conditions influence the WUR? The WUR increases with increased light levels, increased temperatures, lowered humidity, moderate-to-high wind speeds, and long days.
Conversely, the WUR is reduced during overcast, humid, cool, still, and short days or in shady areas.
During the past few weeks of little precipitation, much Illinois turf has been under severe drought stress because of high WUR.
While temperatures have been moderate, the light levels, humidity, wind speeds, and day lengths have favored a high WUR.
These conditions have intensified problems in areas where the turf is shallowly rooted due to heavy spring precipitation and water-logged soils.
As conditions become hotter and more humid, irrigation practices become a dominant aspect of the management scheme.
Adjust turf irrigation rates to the present needs of the turf, not to a preset schedule or clock.
Supply adequate water to maintain turf quality, but be aware that even though temperatures increase, turf WUR may not due to increased humidity, decreased wind speeds, and shorter days.
Time irrigations to allow for foliar drying to reduce disease potential.
Note that syringing, even under times of low humidity, probably has only temporary impact on turf cooling, while during times of high humidity may increase disease potential.
In previous Turfgrass Tips, we've discussed the importance of management practices that enhance turfgrass rooting.
Although writing it repeatedly likens these musings to a broken record, employing cultural activities that encourage turfgrass rooting continue to be important.
Enhanced rooting, when combined with knowledge of turf water use rates and proper irrigation management, can result in quality turf better able to withstand the onslaught of the remaining summer.
(TOM VOIGT AND BRUCE BRANHAM)
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