host posted on January 17, 2010 19:20
YOU AERIFY YOUR GREENS EVERY TWO WEEKS? Bah Humbug!
NOBODY IS HAPPY! Too much water! Not enough water! Poor quality water! How do we deal with water issues and are we sure that our issues are really with water. The upper Midwest is having a mighty tough time with excess water, giving a whole new meaning to floating greens. Throughout much of the rest of the country, there is hope for rain or grumblings of wanting a bit of relief from the lack of rain. So how do we deal with water when it comes to providing top quality turf and an exceptional playing experience?
Let's take a different twist to the issue, beyond the obvious. If the greens are underwater, they have got to be drained and in the upper Midwest it will take an act of Mother Nature and time to allow for the waters to recede. But once the waters recede, what's next? Remove the debris from the surface, get some much needed oxygen into the root zone and where necessary it may be time to replant.
Under drought conditions, something entirely different happens. The high ET (evapotranspiration) rates cause a loss of water from the root zone and encourage us to apply irrigation water frequently. These high ET rates bring a silent partner into the cultural mix, however. As waters evaporate from the soil surface salts begin to accumulate, and if left unchecked can cause the surface soils to seal against water infiltration or gas exchange. Our natural tendency is irrigate some more and consequently once again we find ourselves lacking sufficient soil oxygen. (If salt is accumulating in your root zone you HAVE to get rid of it through leaching, or flushing.) What is missing is an adequate supply of oxygen to stimulate and support new root growth and development. If you are fortunate to have a sub-surface aeration system you can mechanically extract the excess water and draw fresh air into the root zone – assuming you didn't blow a fuse and provided you have a place to put the water. Simultaneously it is imperative that the root zone be opened to allow for excess water to escape through evaporation, and oxygen to enter to support life in the root zone. This can be accomplished using coring tines which will leave a physical residue (the core) to deal with, or through solid tine aeration or "venting". Regardless, the result is to produce large pore spaces in the root zone which allows for a free exchange of moisture and air. Actually I like to think of this as manufacturing macro-pore space.
As greens age, there is a loss of macro-pores (air space) and a net gain in micro-pores. Since micro-pores hold water you can expect an increase in water retention in the root zone, and consequently a loss of soil air (oxygen). Older greens will have a tendency to become saturated much easier as their macro-pores degenerate, and as with flooded greens, they will quickly lose their supply of soil oxygen. So how do we solve this problem? Simple, make more macro-pores to hold more oxygen – AERIFY EVERY TWO WEEKS.
Greater gas exchange is supported by generating more macro-pores as well as more rapid evaporation from within the root zone area.
Imagine if you will it's a hot humid day, you have roots of your favorite grass (bentgrass, Poa, bermuda grass) growing deep into the soil profile of your 3-5 year old USGA type green (any green for that matter). What happens next in the heat of the summer when you receive a much needed 2" rain? Reasonable odds, unless you are proactive in your cultural program; your roots will die back and you'll spend the rest of the summer trying to grow grass, rather than spending the rest of the summer growing grass. Gravity cannot remove sufficient water fast enough when it comes in deluges and consequently the air supply is quite limited. The plant and root system is struggling to exist in a hostile environment and by comparison is running a marathon. The increased respiration in the root zone begins to tax the limited oxygen supply, the soil temperatures increase due to high ambient temperatures, both the plant roots and the soil microorganisms quickly suffocate and without relief will either die back or at the very least become inactive. If the profile was managed to have an optimumized balance in macro and micro pores drainage would be accelerated, gas exchange would be more favorable and roots and microbial activity would be sustained. AERIFY EVERY TWO WEEKS.
In reality, "venting" = solid tine aerification every two weeks is a proactive process which will enable the excess moisture to evaporate, maximize gas exchange and support both microbial activity and plant root growth and development. In the event of a heavy rain it will allow the root zone to dry quicker and restore its balance in soil moisture and soil gases.
DR. MILT ENGELKE, University of Texas A & M