How low can a green’s moisture go?

By |  May 20, 2013

Do you think 8% moisture would kill your greens? Could they thrive at 12%? How about 16%?

While most irrigation systems today have sensors that will turn on the water at a certain point, few superintendents have the faith or courage to allow their irrigation systems to run on their own. Every day or two they send an assistant out with a hand-held meter to poke greens and look for dry spots and consistency.

Some superintendents see numbers below 20% as “hard and dry.” Just how low can you go? And will the auto-sensors keep you out of trouble?

Kevin Frank, Ph.D., and Emily B. Merewitz, Ph.D., both at Michigan State University, aim to find out. In a two-year study co-funded by the Michigan Turfgrass Foundation, they are going to look at the effects of drought and traffic stresses on physiological responses and water use characteristics of creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua).

“The technology is there. The question is, does anyone trust it enough?” Frank says.

The project has been a while coming. The greens for irrigation at MSU were built in 2008. There are 9 blocks of Poa and nine of A-4 bent. Each block has a moisture sensor and those sensors will water the grass at 8%, 12% and 16% by volume – each automatically.

“I’m good with the technology and we will see how it runs,” Frank says.

There will be three traffic treatments, too: none, low and moderate. Merewitz will look at sensing hormones and rooting characteristics in each block.

Still, 8% seems desert-like for most USGA-spec greens. We had to ask: If it is too dry, will they let the green die to prove the point?

“The beauty of this experiment is it takes me 10 seconds to bump it to 9% or 10%,” Frank laughs. That’s a luxury most superintendents don’t have. However, the results of this two-year test may save greens elsewhere. Stay tuned.

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