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.
In the performance evaluation of the bowling green, one of the key factors is turf grass density which is important due to its ability to influence other performance factors and in monitoring bowling green and soil health generally.
The Performance Evaluation of the Bowling Green we embarked on last time relies on our ability to appraise a range of factors. Some of these are purely visual, while others are functional and can be quantified more readily. The trick lies in gaining the experience to merge the visual data with likely performance traits. Good old fashioned greenkeeping and the greenkeeper's "feel" for the turf are still as relevant as they've always been. Today we get started on the process of evaluating bowling green performance.
The Role of Microorganisms in Soil Health is vast and in many cases misunderstood. For decades we have been obsessed with the potential harm that just a few pathogenic microbes can cause, instead of learning to think of the soil as an eco-system. We've learned the hard way about that approach and now that pesticide availability is being reduced we need to start taking this seriously. Excellent article here from Christopher Johns, Research Manager, Northern Australia and Land Care Research Programme
Grass identification is a key skill for the greenkeeper and over at the Bowls Central Academy the students have been spending a fair bit of time recently finding out about that and all of the things that can go wrong on and under the green. They have then applied this learning to their own greens to enable them to develop a sound maintenance and renovation program for their greens.
By far the best selling of my eBooks available on this site is Performance Bowling Greens; it out sells all of the others by 10-1. Bowling green performance can seem a bit sketchy and hard to tie down to any sort of measurable parameter, but that's more to do with the lack of a joined up approach to the subject in the industry than it is a lack of measurable components. This article introduces the subject of the Performance Evaluation of the Bowling Green.
In nature, it is often said that things will tend towards chaos and this is described by a mechanism known as Entropy. In one of his recent TV programs, Professor Brian Cox demonstrated this using a sand castle as his example. Simply put, Entropy says that due to natural movement by wind and weather, sand is highly unlikely to form itself into a sand castle. However, a sand castle is highly likely to be converted to a pile of sand. This is Entropy in action and it seems to say that nature prefers chaos to order; but, whose description of “order” are we using for this?
What if nature was viewing the sand castle as chaos and was instead trying to make order of it by turning it back into a nondescript (as far as we are concerned) pile of sand?
The fact is, that instead of chaos:
Natural systems will tend towards equilibrium.
A common example of this tendency towards equilibrium is the wind we feel on our faces every day. Wind is caused by uneven warming of the earth’s surface. Where one area is warmed more directly, the air above it will rise. This creates a space for cool air. When that cool air rushes in to fill the void, we feel it as wind.
So, although these processes might look like chaos to us (when our sand castle is ruined), it’s really the opposite to chaos that’s happening:
Natural systems will tend towards equilibrium.
This is the way of nature and it informs and drives a lot of what goes on in and around the grass plants on the bowling green.
Today, we will look at two mechanisms of turfgrass physiology that active in our grass plants and soil and that follow this tendency towards equilibrium, without which our turf wouldn’t be able to grow and thrive.
The first of these mechanisms is called Diffusion which is a term you will find throughout science. In broad scientific terms Diffusion explains the process through which molecules mix as a result of their energy and random motion.
In more simple terms related directly to the management of bowling greens, we see Diffusion in three distinct plant growth processes. We can think of it as a process that makes molecules move from an area of high concentration to an area of low concentration.
When we looked at the basics of Photosynthesis, we discovered that our grass plants absorb Carbon Dioxide (CO2) from the air through their leaves. Diffusion is responsible for this process; as the CO2 moves from an area of relatively high concentration (the air) to an area of relatively low concentration (the interior of the grass plant leaf). So Diffusion is a very important process in the cycle of food production for the plant.
The second of these growth processes affected by Diffusion is the way in which soil borne nutrients are moved towards the roots of our grass plants to enable them to be taken up by the roots. These nutrients are present as ions in the soil. These nutrient ions can spontaneously move from a point of higher concentration to a point of lower concentration by Diffusion. This happens in the soil because the immediate root area, once it is depleted (by the roots sucking them into the plant in the soil water), has a lower concentration of the nutrient ions. In this way, the soil around the roots remains in equilibrium with the greater soil mass.
The final of our three examples of Diffusion at work is called Transpiration.
Transpiration is the process by which the plant loses water to the air through the leaves. It is essentially a mechanism by which water evaporates out of the plant to the air. This evaporation happens through the leaf stomata, the same tiny holes in the undersides of the grass plant leaves that are used to take in CO2. This is another example of Diffusion in action, as the water vapour moves from an area of relatively high concentration (the interior of the leaf), to an area of low concentration (the air)
Transpiration is an essential part of the mechanism by which plants continually take up moisture and nutrients from the soil. The combination of the Transpiration Pull (of moisture out of the plant to the air) and the sucking up of water (and nutrients) by the roots from the soil creates the effect of a continuous pump that moves water and nutrients around the plant to where they are needed. In the process, it gives the grass plants some of the functional qualities required to produce a Performance Bowling Surface.
This sucking up of soil nutrients in soil water solution brings us neatly to the second of the mechanisms that keep this natural balance, Osmosis.
Osmosis is the name of the process in plant growth whereby water molecules move from an area of relatively low concentration (of solute nutrients) to an area of relatively high concentration (of solute nutrients). Osmosis then is the mechanism used by the plant to take up most of the water and nutrients it needs.
Direct root interception of nutrients.
Root hairs make direct contact with nutrients in the soil, but can only impact around 3% percent of the soil volume. Symbiotic relationships with Mycorrhizae can increase the soil volume that roots are able to extract nutrients from.
Grass plants, sucking up water through the processes of osmosis and transpiration also move the nutrients that are dissolved in this water up through the plant. Some nutrients are more mobile than others due to the relative weakness of their electrical charge (or polarity of it) and are usually always available in soil solution. The Nitrate form of Nitrogen is quickly available to plants due to this, as are other mobile nutrients like chloride and sulphur. Calcium and magnesium are only loosely held by the soil and are easily brought into the soil water solution. However, some other nutrients are held tightly to what is called the soil colloid and are much less easily accessed by the plants.
Next time we will look at the process that dictates the availability of soil nutrients.
The breakdown of sugars to release energy in a process that provides the chemical energy source for all cellular activities. Respiration depends on a supply of glucose (from photosynthesis), oxygen and suitable temperature.
Last time I introduced photosynthesis, one of the key processes in turfgrass physiology, used by plants to produce their own food. This happens when the plants use the photosynthesis process to turn carbon dioxide taken in from the air by the leaves into a simple sugar (glucose) product that can then be used to fuel the growth and build tissue in all areas of the plant. We saw how the glucose can be used immediately to fuel the plant’s internal processes, or be stored as starch for later use.
The plant uses a process called Respiration to drive growth and development. In much the same way that we respire, i.e. burning food to grow, develop and keep our bodies healthy, plants burn the food created by photosynthesis to fuel growth and to build and repair all of the component parts of the plant.
A simple way to think of Respiration is that it is almost the opposite reaction to Photosynthesis. Here’s how it looks:
Glucose + Oxygen ——————> Carbon Dioxide + Water + Energy
You will see from the equation above that in addition to the energy developed, there is quite a lot of by product in the form of CO2 and Water. Respiration is quite a wasteful process and a lot of the energy produced is given off as heat into the bargain.
Respiration takes place in all plant cells but can only use one source of fuel and that is the glucose or starch already produced by photosynthesis. This means that Photosynthesis and Respiration are locked into a kind of race. As Respiration fuels growth it is said to assimilate the products of photosynthesis i.e. assimilate the food into plant tissue. This means that for good steady plant growth, photosynthesis must produce more food than respiration requires. The measurement of this is called the Net Assimilation Rate (NAR). We will look at this process in a bit more detail in a later article, but for now it’s enough to know that when photosynthesis can’t keep up with respiration, growth and repair will slow down or even stop.
Respiration operates continually even at night and of course Photosynthesis only happens in sunlight. Both processes require a suitable temperature to work also. This explains the slow down of growth in the cooler, darker months. It also explains the need for different turf management practices where there is shade.
If photosynthesis stops or is even reduced, the plant becomes unable to grow and becomes semi-dormant. With our cool season grasses in the UK, semi-dormancy is usually the full extent of the slow down we see. In a warm winter week, we will usually see a restart of growth and we will probably need to give the green a cut a few times over the winter as growth doesn’t usually stop completely.
However, there are transition zones around the world where it is too hot in summer to use cool season grasses and too cold in winter for warm season grasses, and in these areas the warm season species’ can experience full dormancy where the grass turns completely brown or yellow for the entire winter period.
Dormancy aside, if the plant is to survive, then respiration must continue even in the winter and this is why we see a completely natural receding or shrinking back of the grass plants on our greens even if we leave them mown at a fairly high height of cut at the start of winter. The plants start to use up some of the starch reserves saved in the good days when NAR was low (photosynthesis easily keeping up with respiration) in the roots, stems and crowns of the plants. When this reserve is depleted, the plant must conserve energy by reducing its biomass. Roots will recede and leaf tissue will be sacrificed for the greater good of winter survival.
To wrap up for today, Respiration is the process used by the plant to convert food into plant tissue and is the main driver of growth, repair and reproduction in the grass plant. When photosynthesis (production) is greater then respiration (consumption) then growth will continue unabated. When the opposite happens, then growth slows and semi-dormancy can occur.
Next time we will start to look at the internal mechanisms the plant uses to take in water and nutrients.