Monday, August 10, 2009

Trees, rough and water deficits

April through October are the most active months that our rough turf is growing. Certain signs of stress will show up where the turf is thick and difficult to play out of or might be thin and weak. Some of the stressed, thin turf is caused from the heat as well as some disease but most of the stress is related to moisture deficits in the soil. During periods when we receive a nice amount of rainfall every week from 1/2 an inch up to 1 inch, the turf will stay in fairly good shape. There is adequate water for the turfgrass underneath the trees and for the trees. Once temperatures become high and rain is reduced, we begin to see rings underneath trees where the roots of the trees out compete the roots of the turfgrass for moisture. These rings usually go out to the drip line of the tree which is basically as far out from the trunk of the tree that the braches stretch. Over this past week, we began to see some of these issues.

The picture below is looking from about the 150 yard mark on #12 back to the tee box. You can see the stronger turf to the left 1/2 of the photo and the weakened turf toward the tree line. Some of the weakness in the turf on the right is because of the turf species that dominates this area. Poa annua is highly competitive underneath the tree area and is the dominant species. The turf to the left consists of turf type tall fescue and bluegrass/poa annua combination. These grasses can handle the higher light that is received along the fairway. There are no species that will grow vibrantly under full shade and very dry conditions mowed at golf course rough height in our climate. We have a very good irrigation system but there are weaknesses in every system. Most systems do not adequately place enough water under tree lined areas.

A majority of our system is set up the following way. Each fairway has a row down the middle and outside each fairway in the rough on both sides there are rows of heads. The heads turn full circle. The middle row of heads are used less frequently because the rough turf requires more water than our zoysia fairway turf. If we run our center rows or even our outer row heads an excessive amount, this can lead to the zoysia fairways to be weak and creates a soft, unhealthy golf course.

The heads run in a line from tee to green and are spaced about 75" apart which allows for a majority of the heads to overlap other heads in a full circle. We also have additional heads throughout the course between areas 1/18, 16/17 and other areas so that a majority of the property can have water at any one time.

The picture below is from about 100 yards out on #3 looking up toward the green. One of the benefits that the new irrigation system gave us beside a much improved system, when the larger main lines were trenched in place, the roots of trees were pruned. The trench went about 24-30" deep which literally cut the roots of the trees, basically pruning like you would do a shrub above ground. In the picture below, the main line runs up the right side of the trees. This is where the trencher went. It takes a few years for the tree roots to begin to compete for moisture and nutrients again. Some stress can also be created by high concentration levels of cart traffic in some areas. This is why carts are asked to stay in fairways to reduce the impacts on our rough turf.

The picture below is looking back toward 4 tee from about 50-75 yards from 4 green near the 5 tee area. There is also a main line that runs to the left side of the trees in this area. You can see that the turfgrass is not match for the trees when it comes to the ability to take up water. Also more light creates healthier turf. Some of the turfgrass near the fairway is bermuda grass. As you know, bermuda is a horrible rough to play in at 3" or more but is very green in the summer. The majority of the turf in the left side of the picture is cool season turf. As we get closer to September and weather continues to benefit our turf, we will begin to lower our height of cut in the rough.

What can or should be done to improve this situation?
  • Continue to monitor mowing heights and reduce the mower frequency in areas that have weaker turf.
  • Replace larger 11 foot rough units with smaller and more maneuverable units that can easily avoid worn or weak areas.
  • Improve water to these areas by placing some heads which line the fairways to part circle which will double the amount of water to some rough areas. This could create a deficit in the fairway. We would need to monitor this situation to make sure we are not making negative impacts to our zoysia fairways.
  • Add heads where practical and possible. We do pay for water to recharge our irrigation lake once it is at a certain level. A couple of nights using 200-300 thousand gallons of water will require the tap to be opened.
  • Improve and increase aeration to tree areas. We need to improve aeration to all rough in general and use soil penetrants or wetting agents in heavy tree areas. Aeration also reduces weed populations because the turf grass is stronger and conditions such as compaction do not encourage the growth of knotweed which is one of our more prominent weeds.
  • Removal of selected trees which reduces tree root competition, improves sunlight and allows for more desirable species of turfgrass to survive or be planted in these areas.

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