Monday, 17 October 2011

Soft Spots on the Fairways

Right side of hole 8 fairway is in continual shade year-round

If you have golfed at Pender Harbour recently you would have noticed a few soft spots on our fairways.  In recent months I have had a number of members come to me wondering what the problem with these areas was.  They would often blame the soft conditions on over-irrigation and not enough drainage.  Some even blame the soft conditions on broken irrigation pipes!  At first glance it would be very easy to think that these were the cause of the soft conditions on our fairways.  These soft areas are in fact the result of an unhealthy thatch build up.  In order to understand why we have this thatch problem and what can be done to correct it we need to understand exactly what thatch is.

Thatch is an intermingled organic layer of dead and living shoots, stems, and roots of grasses that develops between the turf canopy of green vegetation and the soil surface (Beard, James B.). It is caused by the turfgrass growing faster than the clippings can decompose.  Increased turf growth and excessive moisture can lead to the production of thatch in turf.  Environmental conditions, turfgrass species as well as nitrogen fertility are a few factors that impact the rate at which turfgrass grows.  Excessive moisture is caused by over-irrigating, poor subsurface or surface drainage and shade.

Normally thatch is not a problem and is an important part of healthy turfgrass but when its depth exceeds 0.5" on fairways it starts to become a problem.  Thatch has very little structure and when it is wet it results in a very soft playing surface.  Thatch is like a sponge.  It absorbs water and can holds onto it tightly.  If it is dried out completely, it too is like a sponge in the fact that it will become very difficult to re-moisten.
2" thick thatch layer on hole 1 fairway. Note roots do not
penetrate into soil.

It is also interesting to note that turf roots growing in thick layers of thatch often don't even penetrate into the actual soil.  This can be easily seen in the following picture.  This become a problem as the roots are often shallow and if the thatch layers are very difficult to evenly irrigate in the dry summer months resulting in patchy brown spots on our fairways.  
Next we need to look at the physical characteristics of each of the problem areas.

Almost every soft spot on our fairways in on sloping ground.  This rules out surface drainage problems.  Any areas on our course with surface drainage problems have been dealt with using subsurface drainage and  surface catch basins.

Landing zone on hole 2 sees very little sun
Most of the soft areas are on soil that is highly compacted. Highly compacted soil has very little pore space available for water or air movement and makes it hard for water to move downward through the soil profile.  This is a result of high soil clay content, cart traffic and our inability to adequately aerate our fairways.  Our fairways contain more rock than soil in many areas and would completely destroy any aerator in minutes!  We have a tow-behind rotary aerator but it doesn't have the ability to penetrate the soil.

Bad spot on 2 fairways sees very little sunlight

All areas also see an excess of moisture especially when the turf is actively growing.  Many people often blame the maintenance department for over-irrigating but in fact this is not the case.  During the summer months we have to find the fine balance where we can keep just enough moisture in the thatch areas as to not let them completely dry up and die.  This is very difficult especially with our out-dated single row fairway irrigation system.  Over irrigation is also only possible when we are actually irrigating.  We normally only irrigate during the months of June, July, and August.  During these months the growth of our cool-season turfgrass slows to a crawl and therefore thatch accumulation during this time is less of an issue.  Keeping a healthy balance of moisture in the soil is important to encourage the microbial breakdown of the thatch during the warm summer months.

Times of the year when our turf is rapidly growing are in the spring and fall when we have absolutely no control over the amount of water.  These times of year see rapid growth and huge amounts of rain, the holy grail for thatch production.

Sometimes subsurface drainage is required as in this case
on hole 6 fairway
One common condition that all of these area do share is shade.  Every single soft area on our course is on the south edge of the tree-lined fairways.  These areas often see very little direct sunlight even in the summer.  The shade keeps these areas cool and prevents these spots from completely drying during the day.  This in turn reduces the rate of decomposition of the thatch.

So now that we have looked into what causes thatch on our course we can say that our two main issues are shade and compacted soil.  There are two things that we need to do to solve the thatch issue on our fairways.  Firstly we need to eliminate the causes of the thatch and  Secondly we need to correct the actual problem areas.

Shade issues are easy to solve and usually very inexpensive.  I like fix shade with a chainsaw!  Most people fail to realize that just like the turf on our course, the trees too are growing.  In our part of the country we can see trees grow upward of 10 feet a year!  This combined with the fact that the trees are already 200+ feet high!  If nothing is done to reduce the amount of shade on our fairways we can expect to eventually see very little sun anywhere on our course.

3.5' think thatch layer on hole 2
The problem with tree removal is that for some reason it is very emotional for some people.  We need to come up with an inventory of our trees and selectively "prune" (about 2 feet high) a select number each year to maintain a healthy amount of shade (if there is a healthy amount).

The next problem is reducing the soil compaction.  I have already explained how using an aerator would be very difficult so that is not an option.  What we can do is topdress the areas with excess thatch in an attempt to build some structure into the profile.  By topdressing sand into the thatch we can somewhat firm up the conditions and help air and water more freely move up and down through the profile.  Sand is expensive but the areas that it is needed are few and if we can correct the shade we will see much less thatch.  If you don't believe me just take a look at any North side of our fairways.  Not a single soft spot can be found to the north!

The final problem is helping the thatch layer decompose faster.  We can verticut these areas in the summer when they are drier and pull out a good amount of thatch.  We would then rake it up and dispose of it in our compost pile.  This process physically removes the thatch from the problem areas and hastens the firming effects of the sand topdressing.  It will also help the sand move through the thatch layer quicker.

With adequate shade reduction and occasional sand topdressing and verticutting we can solve our thatch issue on our fairways.  We just need to dedicate a small amount of funds for sand and come up with a plan for tree removal.


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