Turfgrass Physiology; Diffusion & Osmosis,

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.

Mass flow

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.

Turfgrass Physiology, Respiration

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.

Turfgrass Physiology, an introduction

Grass Identification

Over the next few posts we will look at some of the magic that occurs within that green square just outside the clubhouse window. Today I’d like to introduce you to turfgrass physiology

Plant food.

Now, if you’ve been down the garden centre or you’ve been watching the gardening programs on the telly, you will be familiar with the concept of plant food, but what we usually think of as plant food is in fact fertiliser  and plants, including the grass plants on our bowling greens…don’t eat fertiliser. There, I’ve said it!

In my introduction to bowling green ecology (now a free eBook) I explained some of the miraculous things that go on within the turf and soil, but these are but nothing compared to the stuff that goes on within the grass plants themselves.

If not fertiliser, then what do grass plants eat? And if they don’t eat fertiliser, then why do we continue to spend money on it?

The fact is that the grass plants on your bowling green make all of their own food in a process called Photosynthesis.

What is Photosynthesis?

The word Photosynthesis is derived from a combination of two Greek words; Photo, meaning light, and Synthesis, which means to put things together (in this context more precisely it describes the production of chemical compounds by reaction from simpler materials). Photosynthesis is the plant based miracle that guarantees our own existence as well as that of the bowling green.

Each of the grass plants in our green is akin to a little factory where Carbon Dioxide and Water are broken down and converted to a sugar based plant food that can be used immediately to fuel the plant’s growth processes or converted to starch and stored throughout the plant for future use. The energy required for this to take place comes from Sunlight (hence the Photo part of the name) which the plant traps and harnesses in the green tissues. It’s interesting to note that plants get their apparent green colour from the fact that they don’t use the green portion of the light spectrum. instead they reflect it back, giving them their green appearance.

In a fortuitous twist the photosynthetic process creates a waste product called Oxygen, otherwise there could be lots of bowler-less bowling greens:-)

We will look at Photosynthesis in more depth as we go through this short series on plant physiology, but for now here is the basic formula for photosynthesis:

Carbon Dioxide + Water + Light —-> Sugar + Oxygen

Simply put, the plant absorbs Carbon Dioxide gas from the air through the leaf and converts it to a sugar based plant food using Water, which it takes up through the roots, in the presence of sunlight energy.

Why do we use Fertiliser then?

Plants need a series of essential nutrients to fuel a range of metabolic processes and to build specialised tissue. They get these nutrients directly from the soil in the solution they take up through the roots. In a perfectly balanced eco-system there would be no need for us to help out by adding fertiliser to the soil, but since we routinely take away the grass clippings (which would naturally be re-cycled to re-introduce nutrients to the soil) we need to supplement some nutrients, especially Nitrogen which is depleted most rapidly by clipping removal. Later, we’ll investigate these processes further.

Next time we’ll find out what the plant does with all of the food it produces.

done for you greenkeeping schedules

ring binder report

Done for you greenkeeping schedules. Instead of relying on guesswork, hearsay and myth, wise clubs are putting their faith in science and proven agronomic expertise to help them draw up the correct greenkeeping schedule for their greens. In this article we explain how you can easily tap into John's Master Greenkeeper expertise and have a "done for you' greenkeeping schedule for your green.

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Fix your bowling green step 3

Root mass is important for a healthy bowling green

In parts 1 and 2 of this series on how to fix your bowling green, we discussed the process and importance of taking regular soil profile samples and discovered what the soil sample can actually tell us about the condition of the green. In part 3 John links this to demonstrate why each of the visual signals from the soil sample point clearly to one or more of the multitude of issues we experience on poorly performing greens. From disease outbreaks to skinning of heads and bad runs on rinks, the humble soil profile sample can tell us a lot about where we're going wrong and point to the answers that will help us create a performance bowling green in the near future.

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Fix your bowling green step 2

Thatch Layer

In this article we take the soil samples you removed in Fix your bowling green Step1 and look more closely at them to discover what's going on under your green. This is one of the most valuable practices that any greenkeeper can undertake as it can reveal a wealth of information about the condition of your green that you could previously only guess at.

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Fix your bowling green step1.

Smoothness and Colour

I genuinely believe that it's possible to come up with a formula to fix your bowling green, regardless of it's current condition. This is due to one over-riding fact that I've discovered after looking at literally hundreds of greens. They are all at some stage of what I've termed the Circle of Decline. The critical factor in making this possible is simple. You must know what you are dealing with and there is no way to find that out without carrying out some hand dirtying investigative work. So let's get dirty!

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Mair Sand

mair sand

"Mair sand" was the call from Tom Morris the most famous and respected greenkeeper of them all, but have we misunderstood him? In reply to an article about fine, firm golf greens John Quinn highlights the similarities between the plight of golf and bowls greens and clears up the apparent contradiction between modern day problems with inert greens and the Tom Morris philosophy.

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The Great Top-Dressing Debate

Top Dressing Bowling Green

Towards the end of every bowling season thoughts start to turn to the autumn renovation program or the “closing of the green” as many clubs call it. Bowling clubs throughout the UK will take delivery of between 3 and 10 tonnes of very expensive top-dressing compost, which will be applied to the green after hollow tining or some other aeration operation, in the belief that this will ensure that the green is in perfect condition next season. However, too much top-dressing can actually  harm the green and in many cases, clubs simply shouldn’t be doing it at all…but why?

The answer is simple yet full of complexity. At it’s most basic, the answer is that excessive use of sand on bowling greens causes the under lying soil to become inert; lacking life or the complex web of interactions that go to make healthy, high performance turf. The natural balance of the soil/turf ecosystem is upset and the green will never be capable of consistent high performance for as long as the folly of top dressing is allowed to continue.

The complexity comes in when we start to consider that top dressing is recommended by most experts and consultants and that this advice is religiously followed by the vast majority of bowling clubs. However, a brief look at the facts facing many bowling greens after decades of this type of maintenance makes it perfectly clear that top-dressing is not a good option for the majority of bowling greens in the UK.

In the remainder of the article I want to explore the issues I have experienced with greens that have been routinely top-dressed using high sand top-dressing composts over the past 30 years. I will explain the problems with Localised Dry Patch, Thatch, Soil Exchange, Green Levels and Surface Smoothness, Irrigation and water
management and the dilemma that all of this leaves many clubs facing.

So lets’ start with Localised Dry Patch or LDP.

Localised Dry Patch

Over the last 20 years Localised Dry Patch (LDP) has become a major problem on bowling greens, and although this is not wholly attributable to top-dressing, the excessive use of sand in the top-dressing mix has caused water retention problems on a lot of greens.

It is of course desirable to have a free draining soil profile on a bowling green to help to encourage deep rooting of the grasses and to maintain a reasonable green speed for play. However, continued application of bulk sandy dressings is of limited benefit to most greens and actually harmful to many due to their already high sand content and related lack of soil microbial activity.


Natural plant decomposition results in a release of nutrients from dead plant material, but soils low in microbial activity tend to suffer from a build up of organic material (thatch) at the soil surface, which will become much more water retentive than desired. However, the answer to this does not lie with dilution of the organic layer with huge amounts of sand, but rather in reducing this layer through judicious and very regular aeration and core removal and the ongoing encouragement of soil microbial activity.

Soil Exchange

Where the soil is less than perfect for fine turf production, soil exchange programs consisting of hollow tining followed by top-dressing with a more desirable growing medium will still be required, but this is an entirely different subject.

Green Levels versus Surface Smoothness

There is a great difference between “Surface Smoothing” and “Surface Levelling”. Surface smoothness in this context relates to very minor discrepancies in the surface which can be rectified by a combination of surface aeration, rolling and light top-dressing.

Surface levels on the other hand cannot generally be greatly improved through even “Heavy” top dressing work. This term relates to much more severe changes in level which can be measured by laser survey and can be seen to have a visible affect on a wood’s traverse across the green.

“Heavy Topdressing” usually defined as dressings over 6 tonnes will not have a dramatic effect on surface levels and are more in keeping with the type of operation required by new greens for the first 2 to 3 seasons to achieve the final levels not ironed out during construction.

I say this because if you do the calculations, a 10 tonne dressing over an average green (1400 m2) will result in a maximum coverage of 4mm, which is only suitable for smoothing out the smallest of imperfections.

By far the biggest culprit in poor levels is excessive thatch which moves, swells, compacts and contracts continually. Trying to keep up with this with top-dressing is futile.


Going back to the main issue of greens drying out, the average bowling club in the UK is finding it difficult to find the money to irrigate the green sufficiently during dry weather. Again when we look at the numbers, the average automatic irrigation system throws out approximately 1mm of water for every 2 minutes of run time.

Now I visit a lot of bowling clubs and I know that many of them rely on “rule of thumb” measurements like 4 minutes per head etc when timing irrigation. Well, on average a green will lose 25mm of moisture to evapo-transpiration (a measure of the combined effects of soil evaporation and plant transpiration) and that’s from a  healthy green in a normal dry week. This doesn’t take account of excessively high sand content, drying winds or existing dry patch problems etc.

To simply replace the moisture lost from one day’s evapo-transpiration you need to run your irrigation system for 8 minutes per head, that’s double and in some cases several times what many clubs are doing. Over a 7 day period this equates to 50 minutes of run time per head.

Catch 22

Turning back to Localised Dry Patch. This is a condition that causes large sections of the green surface to turn brown due to lack of moisture. No amount of irrigation will make these areas re-wet. They are literally hydrophobic or water repellent. Careful use of wetting agents and hand watering can make some improvement, but usually it takes a wet winter to bring about full re-wetting. The main trouble with LDP is its tendency to make the green bumpy. This happens when the baked dry thatch layer on top of the soil starts to shrink below the surface of the surrounding healthy turf. Irrigation makes the problem worse as the healthy areas grow more and the dry areas recede further.

To crown it all, continued heavy use of the irrigation system in the desperate effort to bring these areas back to life, starts to encourage thatch fungus, which eventually sinks and causes an even more uneven surface.

The Alternative

The Performance Bowling Greens program isn’t completely anti-top-dressing, but I have found that very few greens, at least in the UK, can actually cope with the damage that would be inflicted by applying more sand. The program recognises that some greens will still require top-dressing and gives advice on this.

However, the most important aspect of the programs I recommend for most greens is that they focus on returning bowling greens to healthy, living eco-systems that are not only disease and pest resistant, but also in a condition that helps the club to provide their members with a consistently high performance playing surface that can be set up predictably over the entire playing season.

The Performance Bowling Greens Program is set out in comprehensive detail in Performance Bowling Greens, a practical guide.