Life after pesticides for bowling clubs, what a scary thought, or is it? Master Greenkeeper John Quinn explains why he believes the death of pesticides could be the start of a revolution in bowling green performance.
We are familiar with the concept of our grass plants being composed mostly of water (75-85%), but what else is in a grass plant? The answer is that the dry matter of the plant is made up of a mix of 16 elements, commonly referred to as the essential nutrients. We describe them as essential because the plant can’t exist or complete its life cycle if any of these nutrients are lacking to any great degree.
Bowling Green Nutrition
Some of these elements are used in bulk by the grass plant. These are Carbon, Hydrogen, Oxygen, Nitrogen (N), Phosphorus (P), Potassium (K), Calcium, Magnesium and Sulphur. Some others like Iron (Fe), Manganese (Mn), Boron, Molybdenum, Copper, Zinc and Chlorine are used in smaller amounts. I’ve added the chemical symbol for the ones we commonly see on fertiliser bags.
A large part of this dry plant matter is made up of the three big elements Carbon, Hydrogen and Oxygen. In my introduction to Photosynthesis we saw that the plant takes Carbon (CO2) and Oxygen directly from the air by absorbing them as gasses through the leaf stomata. Last time we looked at Osmosis, the process used by our grass plants to take up water (H20) from the soil and this is where the Hydrogen (H) comes from as well as more Oxygen. The plants can always find an abundant supply of these three elements and if the day comes when they can’t, then we won’t need to be worried too much about how the bowling green looks!
The remaining 13 essential nutrients are accessed via the soil from 2 main sources, but regardless of the source, the grass plant can only absorb these nutrients once they’ve been dissolved and contained within the soil water, more accurately referred to as the soil solution as it isn’t just water anymore.
One source of nutrition is the process of decomposition that happens when plant tissue dies. This organic (carbon rich) material is broken down by soil organisms and micro-organisms and returned to the soil as readily available plant nutrition in the soil solution. This is why the bowling green needs to be considered as an eco system; nothing happens in isolation.
As we saw, nutrients can only be accessed by the plants if they are able to be taken up by the plant roots in the soil solution, but many of the essential elements needed to complete the grass plant life cycle are securely tied up in the soil minerals. These are made available by the slow weathering of the minerals by rain and wind and are washed into soil solution where they are available to the plants. However, the majority of soil nutrients are bound up and unavailable in what are called insoluble compounds.
To be accessible to the grass plant roots, the mineral and organic nutrients must be broken down to their simplest forms called ions and some of these are negatively charged (anions), while others have a positive electrical charge (cations). The most common form of Nitrogen used by plants is N03– which is an anion due to its negative charge, whereas Calcium is taken up as Ca++ which is a cation due to its positive charge, notated as two + signs in its chemical symbol.
These plusses and minuses are important in soil chemistry and in the relative success or otherwise of our bowling green maintenance. More + signs in the chemical symbol for any ion means a stronger bond to the soil colloid, the name given to the negatively charged clay and humus particles in the soil which hold on to cations and stop them from leaching through the soil. Incidentally, this is one reason we need to apply Nitrogen frequently as fertiliser; its negative ions are easily leached out of the soil by rain as they aren’t bound to the soil colloid. It also explains why it is futile to double up on fertiliser applications in the hope of a better result.
Before they can be made available to plants as ions in soil solution between 15% to 25% of the essential nutrients need to be dislodged from the soil colloid by an ion exchange and the relative ease or difficulty of this in a soil is called the Cation Exchange Capacity (CEC). The CEC is simply a measure of how many exchange sites exist on the colloid.
Now here is another of those wonders of nature that is difficult to appreciate when you’re looking out the clubhouse window at that square of grass. The root hairs of the grass plants release hydrogen ions (H+) and when these come into contact with the soil colloid, they each take up a place on the colloid, breaking or weakening the colloidal-nutrient bond of one of the other nutrient ions. Each + in a nutrient’s symbol is equivalent to one exchange site, meaning you need 3 H+ Hydrogen ions to knock a Fe+++ Iron ion off the colloid and into soil solution. Once these nutrients are knocked free they become more available to the plants, where they are taken up in soil solution through the root hairs.
Hydrogen ions H+ are at the very heart of another important soil mechanism called pH, but that’s for another day.
Another very popular subject on this site is over-seeding of greens in Autumn.
Over-seeding is commonly carried out as part of the autumn bowling green maintenance and renovation program and is very often a disappointment.
You would expect this work to quickly fill in the bare patches and spaces in the sward left by disease, localised dry patch and a host of other green problems, but this is very often not the case…why?
The answer to most disappointing results from over-seeding is “competition”. Competition from the mature, indigenous grasses whether fine or weed grasses like annual meadow grass usually reduces the success or survival rate from over-seeding to a very small percentage.
This quite often comes as a surprise to greenkeepers who have observed a very good “take” shortly after seeding (7-14 days). At this early stage it is not uncommon to see vigorous lines of dense new seedlings bursting forth from the green. This however, is usually a false reading.
At this very Read more
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.