T U R F TA L K
Rootzone Examination
on Putting Greens By Chris Hartwiger and Patrick O'Brien, USGA Green Section
T
hroughout the year we hear comments about poorly draining putting-green rootzones or about rootzone profiles that hold too much water. Poor internal drainage in a putting-green rootzone is a harbinger of bad things to come. Scientific research and field observations demonstrate over and over again that when a rootzone holds more water than desired, oxygen can become limited. Poor root growth, black layer and severe decline during periods of high temperatures become serious and real possibilities. Today’s turf manager has more cultivation equipment and amendments than ever before to alleviate these conditions. Before attempting a solution, however, it is essential to identify which portion of the rootzone is holding too much water. A couple of examples illustrate this
point. If there’s a clay layer 6" into the profile and you aerate with 3" tines to help the green drain better, the clay layer remains unaffected and the rate at which water moves through this layer will not change. Conversely, a sand-based putting green with high organic matter in the surface zone and excellent drainage beneath this zone might not receive much of a benefit from deep-tine aeration compared to standard core aeration. A recent article publish by Dr. Bob Carrow of the University of Georgia included an inexpensive and simple test (outlined below) to help you determine which portion of a rootzone is limiting drainage.
Test Your Drainage Step 1: Use an infiltrometer to determine the field SHC and record the value.
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Step 2: While the infiltrometer is still in place, push a 1/4"-diameter solid tine with a sharpened end to a depth of 3" a couple of times into the turf surface within the infiltrometer. Do not go deeper than 3" so that the zone that controls SHC can be identified. Remove the tine(s) from the holes. Repeat the infiltrometer reading. Record the value. If SHC greatly increases after creating macropores just within the 3" surface, then the controlling zone is at the surface. Step 3: If the reading is similar to the initial reading but low for both of the above determinations, push the rod in the same holes to the bottom of the rootzone mix (about 10" to 12") and determine SHC. If readings increase dramatically, this indicates that conditions from between 3" and 12" control SHC, rather than surface conditions.
Conclusion A good balance of air- and water-filled pores is a major contributor to providing turfgrass its needed access to adequate levels of air and water. If poor internal drainage is detected, it is necessary to first identify where the problem lies. Hopefully, the inexpensive three-step test discussed above can aid in this process.
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26
TENNESSEE TURFGRASS
JUNE/JULY 2004
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