Summer Green speed trial Part 1
I do not believe it is possible to discuss our summer green speed trial or compare our cooler month green speed to our summer green speed without first having a very basic understanding of the turf type in our golf greens. Members realise we cut a fraction higher as just one of many precautions in summer to protect the greens and if we don't the greens inevitably suffer, but why?
Our greens are predominately Pencross Bent, what is classed as a cool season grass, this means its main period of growth or when growth is at its strongest is in spring and Autumn more specifically when temperatures are between 15 and 24 degrees Celsius, outside these ideal temperatures Root and shoot growth slows, the further we move away from these temperatures the slower the growth until such time root and shoot growth stops, root growth can reverse, generally around 32 degrees.
All living things need food / energy to maintain health, grow and survive, our greens grass is no different it produces food / energy mainly in the green leaves of the plant through sunlight and gas exchange, this process is called Photosynthesis, the capture and conversion of food / energy.
During the optimum temperatures (15 to 24 degrees C) there is adequate amounts of food / energy produced for growth, as temperatures increase energy production declines and the amount of energy available for vital life functions continue to decrease the further from these temperatures we get.
As this is happening energy consumption is actually increasing, the hotter the temps the more energy the plant uses to survive through respiration (breathing), research shows at 32 degrees energy production is less than energy consumption, the higher above 32 degrees the greater the discrepancy, this imbalance can lead to a total collapse of the biological process in the plant, and death.
The plants natural defence mechanism to overcome this is the capability to store energy, the lower production of energy is supplemented by stored energy in the hope it will have enough stored energy to make the distance to the next period of optimum temperatures where once again the production is greater than the consumption.
We assist this process with our management practices in summer by raising the height of cut slightly; we increase the amount of leaf area potentially increasing energy production giving the grass that little bit extra fuel to survive. Research suggests a 40% increase in photosynthesis can be achieved by raising the heights from as little 0.5mm.
We assist this process with our management practices in spring by aerating, applying soil amendments etc all aimed at increasing plant health, providing conditions for optimum growth and energy storage.
The problem is, it is a natural defence mechanism in a natural state, our greens are not left natural, we mow at extremely low heights, player traffic, traffic from maintenance, environmental stresses from disease and insect pests, temperature, moisture etc are causes of increased energy use, we term these issues as stress placed on the plant.
It is rare that major injury is caused by any one of these factors alone, however any combination eg. Heat and low cutting heights etc can cause serious long term injury or worse death.
All these stresses placed on the greens need to be managed, we move holes and change mowing directions to spread wear, we irrigate to give moisture, we apply turf protectancts for diseases, apply specific fertilisers and various products for strength and increased tolerance to stress but some things are simply out of our control, controlling Mother nature just one.
Our summer temperatures of well over 30 degrees, up around 35 degrees with days of over 38 plus degrees, the bent grass is already under stress from heat, low energy production, there is limited growth, they are less tolerant to other stresses, any damage is not reversible meaning injury recovery is slow if at all, to increase pressure on the greens, it is at this time when disease and pest activity is at a peak. Simply the greens are at their most susceptible to injury already weakened by low energy production, heat stress, low cutting heights and player traffic, add any other stress such as disease or mechanical injury and injury is certain, death a possibility and recovery slow.
We at this time reduce other stresses we can control, we syringe the greens to cool them down, we raise the cut slightly to allow for more leaf area to help the plant with respiration and produce energy, we also introduce alternate mow days, change our fertilising and protectant practices, we effectively remove the stress for the turf in preparing the greens for play.
Unfortunately these practices also cause slower green speeds.
During Spring and Autumn when the turf is at its strongest, they have a very high tolerance to these stresses, meaning it takes longer for injury to occur and should any cause injury, recovery is rapid, a perfect recent example is our greens renovations, or the recent hydraulic leak, a very quick recovery from injury because it was in period of strongest growth and energy production for Bent grass. If this happened in the height of summer or mid winter, it would be months before recovery took place and more than likely in the case of the hydraulic leak, turf replacement would be necessary because the bent grass simply isn't going to recover.
It is at this time we push the greens further, the grass is strong and with careful management, capable of tolerating more intense practices which result in faster greens.
This is why there is a difference between summer green speeds and green speeds at other times.
Another issue we need to be mindful of when talking green speeds and summer, is the direct relationship between green speed and input costs, we can only produce what we can afford, so we must also consider the financial sustainability of any management decisions for green speed.
One final point, for all the above information, is why when I say our summer green speed trial is not to have the greens as quick as at other times, rather to reach a balance between member expectation, turf health and the sustainability of any process we take, there will always be a difference we are just looking at all the implications involved when reducing that difference.