Golf
“Our basic fertility programme over the years at Ealing has been based on two granular applications in the spring to give the plant a good kick up the backside and improve density”
budget. Good soil is essential, which is why the USGA introduced their guidelines back in the 1960s, dictating a predominantly sand based one. Water can now be controlled using efficient irrigation systems supplemented with moisture probes and weather stations. Temperature is, arguably, the most important one. If it’s freezing cold, nothing grows. So, how should we alter our practices to work with the differing temperatures? A new model came about a few years ago which may give us direction.
What is Growth Potential?
Over the last few years, there has been a lot of research from America concerning temperature and how it makes certain things tick. A couple of years ago, an article came out about the growth suppressant Trinexapac-Ethyl. It stated that, if you let the chemical run out of the plant, you ran the risk of the ‘bounce back’ effect, i.e. the plant would then put all its energy into the leaf, causing a growth spurt.
They dealt with this using a model called the Growing Degree Day or GDD. It allows you to regulate the chemical to avoid the risk of bounce back. It is based on monitoring daily temperatures which affect the plant’s metabolism. At the end of last year, I read an article by an American scientist called Micah Woods who, in conjunction with Larry Stowell of PACE turf, talked about the growth potential model. This, again, talked about temperature and how it affects the plant’s ability to take in nutrients. You may have heard of these two before; they have been pushing the minimum levels for sustainable nutrition (MLSN) for a number of years. From their investigations, collating data
from superintendents over a number of years, they think that turfgrass soil nutrient guidelines have been set far too high. Two examples of this were potassium - which they recommend at 50ppm instead of the historical figure of around 250ppm - and calcium at 330ppm instead of 1,500ppm. It seemed to make a lot of sense, so I was very interested in their Growth Potential (GP) model. Growth Potential is, in its simplest terms, a model that indicates when you should apply nutrients depending on the plant’s capability of growing and
absorbing them. The main nutrient that they mention is nitrogen, which is the key element for a grass plant, but the model can be used for other nutrients, such as potassium, too.
Our basic fertility programme over the years at Ealing has been based on two granular applications in the spring to give the plant a good kick up the backside and improve density. This is probably what a lot of guys do across Britain. Normally, we would apply an ammonia based product in March, giving the plant 25kg of nitrogen per hectare, and another in May. So, if you add in a couple of foliar sprays, the greens would receive around 60kg of nitrogen per hectare in a six-week period to bring them in to the season. However, I find that, whilst the greens do turn a nice colour and density improves, the ball roll is reduced as the plant produces a high clipping yield. I also used to see a big kick around June when temperatures picked up and a lot of the residual fertiliser would start to kick in (not perfect for producing that magic growth pattern).
How does it work?
After reading Micah Woods and Larry Stowell’s articles on GP, I decided to contact them as I was keen to give their system a trial over here in the UK. What I found is that they have two models. One is for the cool season grasses that we find in our climate and the other is for warm season climate grasses such as in Asia. They set two different temperature thresholds depending where you are in the world. For cool season they said 20ºC would be a good ball park figure and 31ºC for warm season. But what does this mean?
When you have an average daytime air temperature of 20ºC (add low and high together and divide by two), the plant has the ideal temperature at which to grow and reach its potential. Anything above or below this figure will affect the plant’s ability to grow. Once you know the optimum, then you can start to put together a fertility plan to allow the plant to maximise its potential.
I decided to implement this model on Ealing’s greens for the 2013 season as a trial. If I didn’t like it, I could quickly revert back. A spreadsheet was set up and I inputted all the historical monthly
temperature figures for my location (West FEBRUARY/MARCH 2014 PC 79
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