As the number of pesticides available to greenkeepers diminishes you might have noticed that the term Soil Food Web has started to be banded about more regularly, but what does that mean?
It’s natural for us as clever, sophisticated 21st Century humans, to assume that we are in charge when it comes to our relationship with our turf. As educated greenkeepers we have been encouraged to believe that we can control the outcomes on the green through the inputs we make. And, although we have learned a lot along the way, if we rely too heavily on that belief the performance green will always remain elusive. It’s important to understand that we are actually managing a very complex natural system. The good news, however, is that this hugely complex system can largely look after itself if it is given half a chance. By developing even a basic understanding of soil ecology, we can help ourselves to give it that chance.
Getting your hands dirty
I have the occasional opportunity to teach golf course management students in China. Due to the idea of specialised sportsturf management being relatively young in China, I sometimes have to battle against the assumption that greenkeeping is of lower importance to golf than the higher business arts of Sales, HR and Marketing. Many of my students are already graduates from business school and are joining my class with no intention of ever getting soil on their hands. They want to be managers overseeing the business, so I take great delight in getting them to dig up soil samples and rub the red Chinese earth between their fingers just to see if they can form some kind of connection with the soil and maybe discover that what we’re going to study is indeed worthy of their attention and time. Dressed to the nines in the latest labels, they hate it, but once we get back into the classroom and they’ve had time to wash their hands and get over the horror of behaving like a common peasant, their attitude gradually changes. The remainder of the first morning is spent discovering how we have always had an intimate connection with grass, even if we don’t realise it or ever stop to think about it.
The impact of grass on our everyday lives is massive. The evolutionary significance of grass is huge. Our dabbling in greenkeeping is puny and very recent when compared to our reliance on grass for our own survival.
The family of plants we know as grasses has been around for at least 65 million years and in that time has colonised every continent on earth. By comparison, humans have been around for about 200,000 years, which means that the huge family of grasses around the world managed just fine without us for 64.8 million years. No artificial fertiliser, no lawn mowers, no spikers and certainly no pesticides. In fact it could be argued that it’s the massive success of grass that has enabled our own population explosion and dominance of the planet.
Would you eat grass?
Coming back to my students, I ask them if they’ve ever considered eating grass? Some of them click immediately, most screw up their faces at the thought of it. But the fact is that we all rely on grass to fill our bellies every day. My Chinese students eat rice every day, rice is one of the most successful grasses in the world and sustains a huge proportion of the world’s humans. I tell them that I eat oats, another grass, in the morning, and then eat wheat, also a grass, several times per day after that and so does the rest of Europe and vast tracts of the earth’s human and livestock population; no grass = no meat. In the Americas they eat maize, another mightily successful grass.
Grasses like Wheat, Oats, Maize and Rice are so good at sustaining us due to the high calorific value of their seeds; they are bursting with energy which is readily converted to human (I don’t know what the polite term for human meat is :-), beef, pork or whatever. It’s the seeds we eat as staples all around the world, either whole as with rice, or as flours for making other foods. So far so what?…once pointed out, it doesn’t take much of a leap of faith to believe all of this even if it is awe inspiring.
It’s the origin of that grass seed energy that is the most remarkable thing to discover. Those old 1970’s adverts for Corn Flakes where we were encouraged to get our daily intake of sunshine are actually very close to the truth. The energy in the foods we eat comes directly from the Sun, via the plants of course.
Plants have the remarkable ability to make their own food through the process of photosynthesis. In simple terms this is a complex series of chemical reactions that occur within the green (chlorophyll containing) tissue of our turf grass plants. During this process the plant manufactures sugars out of Carbon Dioxide (CO2), which it takes in from the air through tiny holes in the underside of the leaf called stomata, and Water (H2O) which in takes in through the roots by a process called Osmosis. The energy to drive this process is taken directly from sunlight.
Some of the more fascinating facts about this already fascinating process are as follows:
- Most of the energy absorbed from the sun during photosynthesis is in the blue and red regions of the spectrum. Much of the green part of the spectrum is reflected back, making plants appear green to our eyes.
- The basic photosynthetic process looks like this: 6CO2 + 6H2O ⇒Sun Energy and Enzymes⇒ C6H12O6 + 6O2. Translated into English this means that 6 molecules of Carbon Dioxide and 6 water molecules are converted into one molecule of Sugar (Glucose) and 6 molecules of breathable Oxygen (O2). The glucose is used in the process of Respiration as fuel for the growing process and the Oxygen is given off as a waste product, which is quite fortuitous if you happen to rely on Oxygen for your survival.
- The glucose manufactured by the plant can be moved around to the parts of the plant that need it or converted to starch to be stored for later use.
- The seeds we eat are stuffed with starch which is pure concentrated energy.
- When seeds germinate the starch is converted back to glucose to feed the young plant. This is why barley is malted (the triggering of the germination process), at the start of the brewing of beer or whisky manufacturing process. The malted seeds are then a sugar source for the yeasts to feed on and convert to alcohol.
If grass makes its own food, why do we need to feed it with fertilisers?
That’s a good question. Fertilisers are commonly referred to as plant food and we often say we are feeding the green. The fact is we aren’t actually providing the plants with any food as such, but providing some of the basic building blocks that they need available to them in order to grow the way we want them to.
Plants are made up of four main elements: hydrogen, oxygen, carbon, and nitrogen. With the exception of Nitrogen, these are all readily available to the plant from the soil (water) and the air (CO2). Although Nitrogen is abundant in the atmosphere, most plants can’t extract it from the air and must have it in “fixed” form (ammonia). Some plants like clover and peas can fix (convert to ammonia) atmospheric Nitrogen (N2), due to special structures on their roots which allow them to form symbiotic relationships with specialised bacteria. Our turf grass plants can’t do this and as Nitrogen plays a critical role in key plant tissues and processes such as in DNA, other proteins and chlorophyll we need to add it to the soil where it can be accessed by the plant roots in the soil solution.
So what’s N.P.K all about?
On fertiliser bags you will usually see the letters N (Nitrogen), P (Phosphorus) and K (Potassium). These are the Major or Macro nutrients that are needed by plants in relatively large volumes to enable growth to go on unheeded. Nitrogen, we’ve dealt with already, but Phosphorus and Potassium are usually added as fertiliser too.
Phosphorus is needed as Phosphate to build DNA and an enzyme called ATP, which is a critical enabler of the photosynthesis process, as well as being vital for root development and seed production.
Potassium aids water movement in the plant and helps to build strong cell walls and stem tissue. It is also important to help the plants combat stresses like cold, heat and drought.
Then there are the semi major elements Sulphur, Magnesium and Calcium and the minor nutrients like Copper, Zinc, Boron, Manganese, Iron and Molybdenum, but they can wait for another article.
The Soil Food Web
The reason for the slight detour to fertiliser land was to illustrate the point that although grass plants are perfectly happy looking after themselves, they are actually involved in some remarkable and vital relationships, many of which we can’t even begin to understand. Taking the apparently simple process of applying a bag of Nitrogen fertiliser to the green as an example, you’d be forgiven for thinking that we apply it, the rain dilutes it into the soil and then the plant sucks it up in the soil water and eats it…yum! But what actually happens is much more complex and it relies on a cast of millions to accomplish it.
The Nitrogen Cycle
Here, in very simple terms is what happens to Nitrogen in our greens:
Simply put, Nitrogen exists in our environment as various chemicals like ammonium (NH+4), nitrite (NO−2), nitrate (NO−3). There is also organic nitrogen in the form of humus and partly decomposed organic matter like thatch. Of course there is an abundance of inorganic nitrogen gas (N2), which as we’ve seen can be utilised by some plants. Using various processes, soil microbes transform Nitrogen through a series of different forms, some of which are vital to the health of our grass plants. Without these processes, it would be pointless to apply fertilisers, as they just wouldn’t do anything. The processes of the nitrogen cycle transforms nitrogen from one form to another. Many of those processes are carried out by microbes, either in their effort to take in energy or to accumulate nitrogen in a form needed for their growth.
The Soil Food Web
It’s important that we start to re-think our bowling greens and other fine turf areas. The conventional greenkeeping wisdom has been to assume that we can buy a product or service to deal with any trouble or symptom that crops up. Inorganic fertilisers and pesticides (fungicides, insecticides and herbicides) have come to be accepted as conventional and even essential for green management over the decades since the end of the second world war. This has developed in parallel with agricultural advances designed to enable more efficient food production. In recent times it has even become commonplace for greenkeepers to apply hormonal growth regulators in order to manipulate the growth characteristics of grasses, purely for perceived performance enhancement (greater turf density particularly) and not to deal with pathogenic organisms.
Not only is this approach to greenkeeping damaging to our greens, but it is totally unsustainable, certainly in ecological terms, but more urgently in economic terms. It’s expensive and locks us into a symptom-treatment-symptom cycle that is hard to break out of. Critically it is unsustainable in the face of pesticide bans and withdrawals. In the not too distant future, there won’t be any pesticides available with which to continue this mad approach to what should be a very natural system of management.
What’s the alternative? We need to take a long stride back from the problem to view it more clearly first of all. If we consider the job in hand i.e. to produce a 1500m2 area of fine turf (flat or crowned it makes no difference), consisting of one or two main perennial fine grass species that performs well in terms of speed, smoothness and trueness then the job is clearly defined and we need to do what it takes to support such a facility.
The fine grasses we need to encourage are indigenous to the coastal links and machair lands of these isles, so all we really need to do is create similar conditions for them in terms of the support they would normally have to help them thrive in such places. If we provide them a suitable growing medium and take care to mimic the other conditions they would naturally thrive in, this greenkeeping lark can be relatively easy!
Natural grasslands like this are self sustaining systems, so we need to start thinking of our greens as eco-systems and manage them sensitively in order not to upset the fine balancing act being played out daily in any eco-system. Enter the Soil Food Web.
The soil food web is another way of thinking about the bowls green eco-system. It is a community of organisms living all or part of their lives in the soil. It explains how these soil microorganisms interact with each other, the ecosystem – the soil environment and the plants and animals.
The food web is a way of thinking about the way energy is transferred between organisms in our green ecosystem, much like we saw earlier that energy in a way, as humans, we are totally reliant, albeit indirectly on the Sun’s energy for our survival . The soil food web is complex, but is based on this same idea; that all the energy comes initially from the Sun. Plants use the Sun’s energy to convert inorganic compounds into high energy, organic compounds; taking in Carbon dioxide from the air and minerals from the soil and converting these into plant material by the biochemical process of Photosynthesis we teased out earlier. As part of the constant cycle of death and re-birth, dead plant material is broken down and recycled by microorganisms in the soil ecosystem and this fuels the soil food web as illustrated (simply) below:
Why the Soil Food Web is important to Greenkeepers.
Understanding, or at least being aware of the soil food web is important for greenkeepers for the simple reason that the problem-solution-problem cycle common in greens enduring the Circle of Decline isn’t sustainable either agronomically or economically.
Agronomically, although we have been lulled into a false sense of control by pesticides, you might have noticed that there are fewer of them available to us now. Soon, like in some Scandinavian countries, there will be no amenity pesticides.
More importantly though is the need for greens to improve in performance. Greens that are simply managed around the Circle of Decline perpetually are never Performance Bowling Greens, because they are dominated by shallow rooting annual meadow grass.
If you’re familiar with this site, you will know that there is no ideal place or time to break into Circle of Decline. It’s important that you just start somewhere. This usually means aeration, as a starting point, but there is more that can be done to kick start your green’s recovery sooner rather than later.
Boosting soil microbial activity can be as simple as applying some carbohydrate rich material like seaweed liquid occasionally, but increasingly greenkeepers are also finding benefits in directly boosting soil microbial activity through the application of Compost Tea.
Learn more about compost tea here.