The hot topic at the recent Wisconsin Symposium was managing excess organic matter (OM) in the upper soil profile of greens, especially new sand-based greens. Too much OM accumulation will dramatically change the pore size distribution and increase the ratio of water-holding micropores to air-filled macropores. The end result is poor root growth, slow water movement through the green, and a wet, soft playing surface. Bentgrass decline can occur when these conditions exist during extended periods of hot, humid weather, not to mention other problems associated with wet greens, such as moss and algae.

A sound topdressing program and routine hollow tine cultivation are the best ways to keep OM from becoming a serious problem. Many courses have recently purchased sophisticated topdressing equipment to improve the efficiency of these time consuming operations. Some courses are topdressing greens much more frequently than in the past, but still are experiencing problems related to the buildup of OM in the upper inch or so of greens.

One likely explanation is that the amount of topdressing applied to greens is simply not keeping pace with the amount of OM production. Using new equipment it's too easy to crank down the sand delivery rates to the point where only a light dusting of sand is applied to the green. In the old days, it was one load of sand per green using the Vicon spreader or Mete-R-Matic and then back to the shop to reload. It's not uncommon now to find that one load, using new spinner-type equipment, has the ability to lightly topdress 5 or 6 greens. In effect, the number of topdressing operations increases, but the benefits of topdressing are not realized because the amount of sand applied to greens per season has actually decreased.

Send profile samples to an accredited physical soil testing lab to determine a baseline for the amount of OM present in the greens, especially problem greens. Contact the North Central Region office in Wisconsin at 262-797-8743 or visit the USGA Web site for a list of accredited labs. This is the first step toward developing a sound OM management program. Then monitor and document the amount of sand you are applying to greens each season. The amount and frequency of topdressing can be adjusted as needed to maintain a healthy balance of air and moisture in the root zone. Significant problems will require an aggressive combination of hollow tine cultivation and frequent topdressing.

Safe and Happy Holidays to all!

Source: Bob Vavrek, rvavrek@usga.org or 262-797-8743