In the previous articles in this series, we’ve discovered how to evaluate performance by simply looking for visual indicators on the turf and by gauging some of the functional attributes of grass plant communities when they form turf.
Before we move on to the final stage of this series where we will look at some of the latest and most objective techniques for performance measurement, I wanted to stop for a moment to consider what lies beneath the green layer.
All of the functionality and therefore performance of the bowling green depends on healthy turf and turf is of course not just grass plants. Turf is a construct of a healthy grass plant community containing millions of individual plants, growing in a medium that is suited to sustaining healthy growth and reproduction. The medium is, of course the soil our greens are built on; but what is soil?
If you look at the pie chart at the top of the article you will see the proportions of what I think of as the perfect soil.
In the diagram you will see that 45% of the soil is made of Minerals. The mineral component of soil is usually made up of a mixture of 3 main groups and these are Sands, Silts and Clays. A suitable mixture of these is critical to the soil’s performance as they dictate the soil’s ability to provide nutrition and moisture to the grass plants and suitable drainage. The mix of sand, silt and clay defines the soil’s texture.
The organic component will ideally be around 5% and this is made up of living organisms, micro-organisms and dead, decomposing and already decomposed plant tissue (humus). The organic material is added to by the plants themselves as they produce thatch and the soil organisms break this down to release plant nutrients.
Then there’s the remaining 50% of the soil to look for, but if you do, it might cause you some confusion, because in the ideal soil the remaining 50% of its volume will equate to nothing at all. In fact it is 50% space, or soil porosity to give it the correct name.
Ideally half of this space will be made up of small spaces called micro pores and large spaces called macro pores. The micro pores hold the soil solution which is a mix of water and plant available nutrient ions and the macro pores provide air space and this is where all of the drainage occurs after heavy rain. This air space keeps the soil well oxygenated so that it can sustain a huge population of soil microbes; around 1 billion in a teaspoon of soil.
Sometimes the things we see every day become so familiar that we stop noticing them and this can be the case with the most obvious of performance signals on the bowling green. We can learn a lot from just being a bit more observant of the every day activities we get involved in as greenkeepers.
There are two aspects of green maintenance that sound so obvious that they are easy to dismiss:
- How much grass comes off when you mow? This is called Yield
- And how much grass is left after you mow? Which is called Verdure
It might sound ridiculous to make up special words like Yield and Verdure for fundamental factors like this, but they are important and give us much more information than we might first realise.
This is the measure of how much material comes off when we mow the green. Of course we aren’t interested in the yield in the same way a farmer would be. Our job isn’t to grow as much grass as possible; our job is to grow dense healthy turf that supports the preparation of the green surface to a high performance level, consistently throughout the season. Turf scientists might take the clippings, dry them and weigh the remaining dry tissue matter to come up with an accurate measure of Yield in kg/Ha, but my old boss at my first greenkeeping job had a much more straightforward and instant way of monitoring this. When I returned to the maintenance shed after cutting 18 golf greens in the morning he would simply ask; “did you get much grass?”
Unscientific as that may sound, it’s as good a measure as any to an experienced greenkeeper who treads the same piece of ground every day in life. The subtle nuances of Yield Fluctuation (the increase or decrease in boxes of grass removed to you and me) can tell you a lot about your green’s condition.
Assuming that everything else such as mowing height, sharpness of mower, weather conditions and timing of cut are roughly the same, we can make a judgement of the condition of the green relative to previous cuts we’ve made, whether that was yesterday or last year at the same time. But what can we ascertain from this?
Increasing yield is common after Nitrogen fertiliser has been applied. Fertiliser applications, particularly when using granular fertilisers tend to have a distinct life span pattern and the green will go through a growth pattern after application. For example a few days after application of fertiliser like this it will be common for the yield to increase steadily day after day. At some point after the first flush of growth, yield will level off and stay roughly the same for several weeks. Then it is likely that yield will steadily reduce until a new application of Nitrogen is made and the pattern will repeat. Being able to judge when the next application needs to be made is a skill picked up by greenkeepers over time and relies a lot on watching the grass box filling up. By having this feel for what’s happening in terms of growth patterns, you can form a better understanding of the right fertiliser program, application rates and frequency of application for your green at any given time.
Another key contributor to yield will be the level of plant available moisture in the soil at any given time. Yield will decrease as this dips below optimum and will increase as you get closer to field capacity. There’s a close connection with nutrition here too as fertiliser needs a good amount of soil water for the nutrient ions to be able to get into the soil solution where they can be taken up by the plant roots.
The other non-mowing cultural practices you carry out on your green will also influence yield. Jobs such as scarifying and aeration of any kind will have the effect of introducing oxygen to the soil which will increase microbial activity, releasing nutrients which might increase yield.
Of course, the object is to try to create a steady growth pattern that allows the green to recover from the rigours of play and maintenance and to exhibit all of the other key components of performance we have looked at over the previous 9 articles. Measuring yield even by just counting the boxes of grass collected every day is a great starting point in getting a feel for your green’s performance and the effect that your work has on it over time.
This is a measure of the green plant material that is left after mowing. Oh come on John, I just call that grass, I hear you say, but Verdure is just a little more complex (and useful) than that.
For example in any turf grass species, turf resiliency and rigidity will increase when you leave more tissue on the plant i.e. raise the blades. This will generally increase wear resistance too. Grass will generally be healthier and more robust at higher mowing heights and that is why I recommend raising the height during drought conditions and of course in winter.
Turf resiliency is one of the major factors determining bowling green performance and as such warrants close attention by the greenkeeper. Up to this point in our series on the evaluation of bowling green performance we have been dealing with attributes of grass, turf and soil that depend a lot on the greenkeeper's experience and "feel" for the turf. With resiliency we are getting closer to making more objective measurements.
Turf Grass Elasticity is an important factor in bowling green performance. Today we look a little closer at what this actually means and how it relates to our maintenance and use of the green.
In measuring the performance of the bowling green there are visual and functional factors to consider. Now that we've studied the visual clues we move on to the functional ones in earnest. Today we will look more closely at what at first might seem a strange quality of turf and that is Rigidity. This property of sportsturf is closely associated with the physiology of the individual grass plants we looked at in an earlier series and also with bowling green performance, as it influences green speed and trueness.
Now on part 7, this series has so far examined mostly visual clues to bowling green performance. Moving on now to the functional qualities of turf grass that can be used to make a more tangible appraisal of the performance of the green, we start to get to the point where we can make a quantitative appraisal of bowling green performance.
In the performance evaluation of the bowling green there are visual and functional measurements we can make to ascertain the likely performance of the green. Colour and Smoothness are the last two visual components we need to look at before moving on to the functional attributes we can measure. On the face of it, colour and smoothness seem like fairly innocuous elements to focus on; almost too obvious you might say. Let's see if they are more important or even different to what we previously thought.
So far in this series of articles on the subject of bowling green performance we have used some of the common visual clues to assist in our evaluation of the turf. Today we'll break from that to dig a little deeper into the physiological aspect of the different turf grass species that influence what we see on the surface. Turf Grass Growth Habit can play a big role in the ultimate performance of the bowling green. so let's get started on indentfying the main differences.
In part 4 of our series on the Performance Evaluation of the Bowling Green we move on to examining turf texture. Texture is closely tied in to some of the other aspects of Bowling Green Performance we have looked at so far in this series. Texture is one aspect of turf management that the greenkeeper can influence greatly, but seems so simple that it is often overlooked.