THE BATTLE TO KEEP OUR GREENS CLEAR OF ANNUAL MEADOW GRASS
And ask yourself – Do we need to top dress?
As I see it, the way that most bowling green maintenance has been practiced since 1939 the grass that has survived, despite all our attempts to eliminate it, is Annual Meadow Grass (Poa Annua).
Because the word ‘annual’ is at the front we do accept that it grows from seed to plant during the season and as conditions become unfavourable the plant dies out, but not before it has provided the seed that will germinate when conditions for its existence improve.
This situation has been noted as many as five or six times during one of our seasons alone. The cause of this unreliability of the grass is if the grass gets too hot/too cold, too wet/too dry, too much or too little fertiliser. In each of these cases, the plant makes sure it can continue for the future by throwing up seed heads, distributing the seeds and then the parent plant dies and as soon as conditions are right the new seeds germinate so completing the cycle. It may only need a shower of rain during a drought for the seeds to re-germinate. The seed is only 2mm long and can easily germinate on the surface amongst the dead and dying parent plant.
The reason that they suffer so quickly in the absence of ideal growing conditions is that the roots are fleshy and cannot easily penetrate into the fine soils that compose the root zone existing below the surface. Consequently, the AMG plants dry out quickly as they are not deep enough into the soil to easily access nutrients and moisture. The leaves are continually cut short because, generally speaking, greenkeepers feel they have to drop the height of cut to below 5mm to prevent the seed heads from releasing the seeds and reaching the soil.
This reduction in height of cut only serves to stress out the necessary grasses of Fescue and Agrostis (bents) which can survive ideally down to a 5mm cut, but cutting any lower prevents the leaves from manufacturing its food in its leaves (photosynthesis) and will cause deterioration of the green and the bents will die out to be replaced by AMG.
The quality plants of Fescue and Agrostis have fine deep roots which do penetrate given the assistance of much aeration, travel much deeper into the root zone (food cupboard) where they find their building bricks (nutrients). The root zone is comprised of thousands of un-decomposed roots that rely on air and soil bacterial life to break down these materials to recycle the nutrients contained therein.
As can be seen from the soil profile shown here, there are distinct layers of dead AMG which have been covered over again and again by top dressing year after year for whatever reason.
Apart from the green getting higher and higher by the addition of this material each year, it encourages a better crop of AMG as the seeds will just grow through the top dressing at the exclusion of encouraging the correct grasses of Fescue and Agrostis.
The added height of the green also means that the surface is getting further away from the drainage layer below the root zone. This drainage layer is so necessary to the bowling green surface to enable you to play as soon as possible after rain and is a vital element in the speed of the green.
The soil profiles can and do indicate that many greens are six inches above the root zone instead of being level with the green as it was originally constructed.
We can also see from the soil profile that there has been insufficient practical and regular maintenance procedures carried out, i.e. scarifying the turf (not the soil) to clean out of the debris. It also shows a lack of enough aeration throughout the winter months, as the material would otherwise have been integrated into the different levels of the green.
By not following turf culture and doing the correct regular maintenance of the green you will end up with poor, neglected sandy soil which is ideal for the proliferation of AMG with all its inherent problems.
As previously mentioned AMG can have several seasons in one of our outdoor campaigns and its continuous dying off process will show up as discolouring the turf and disfigure large areas of the green. Eventually, when conditions are right, fusarium fungi will attack the dead and dying AMG plant and cause further disfiguration which needs to be controlled by applications of fungicides. Unfortunately, AMG seeds are not affected by fungicides and promptly germinate when conditions are suitable once more.
So instead of suffering from AMG problems and the rising costs of attempting to control them we really have to come to the conclusion that we must get the right grasses integrated into the turf that can cope with the bowling green maintenance processes.
By and large this means an increase of maintenance throughout the closed season of cleaning out the debris because fungi feed on dead and dying materials and incorporating as much aeration as can be done to increase the re-cycling of the debris that is within the root zone.
Regular scarifying will remove a large percentage of AMG and this will be most effective at the end of the bowls season when the soil is moist or can be moistened by irrigation to create the right conditions for using a scarifier. The Agrostis and Fescues are better equipped to withstand this autumn repair work because they are perennials and are capable of living for several years, whereas the AMG will be easier to remove because of its very poor root system.
Remember always to scarify in different directions on the same day and do not let the blades dig into the soil because contact with the sandy soil will cause extensive and expensive wear to the blade tips. A scarifier is not a soil cultivator, it is to clean out the turf.
Also consider the reason for top dressing the green each year.
Is this really necessary and why are you doing it?
Has the green played better as a result of last year’s application?
Can your club afford the outlay? As a greenkeeper myself, I very rarely used top dressing, other than to build up low spots and then the materials I used were recycled from previous hollow tinings which were compatible to the soil and which were sieved prior to use.
While we are talking about hollow tining, the idea is to reduce the density of the green so allowing new roots to get distributed evenly and maintaining the height of the green at its original level. The holes must be left open for 14 days and do not put the materials back into the holes unless you are doing a soil exchange for a specific purpose.
Under no circumstances should top dressing be placed down the holes, otherwise you defeat the object of reducing the density (compaction) of the green. Two weeks after hollow tining, the bacteria will have been given the chance to work on the debris and solid tining or chisel tining can then be carried out regularly to press the holes together purely by the movement of the tines. This will mean that no extra soil is integrated into the turf, it has been well aerated, the compaction has been relieved and the level of the turf has been controlled and maintained above the drainage layer.
If we take another look at the soil profile you will now realise that a lack of sufficient scarifying and spiking during the closed season has not allowed the correct integration of bacteria activity into the soil by aeration and irrigation. You will also notice the different layers of dead AMG and top dressings applications that have been laid down continuously through the years showing a complete neglect and understanding of correct turf culture practises. You can see that these layers have not been integrated at all by adequate aeration and irrigation. Turf needs moisture, oxygen and nutrients to survive healthily.
The soil profile shows that there has been insufficient care and attention over several years. Top dressing has been applied annually and very little practical maintenance work of cleaning out debris, brushing and spiking etc has been carried out as a matter of course. For many greens this practise has to change if they want to see an improvement in the standard of their bowling green.