Understanding the key elements of Carbon

Carbon, a name that you will most likely have become increasingly familiar with in recent years, and one which fundamentally shapes the planet that you inhabit. What is so special about this element and by which means does it transcend into many areas of turf management? Derek Fullerton aims to provide some transparency to these questions, and ultimately highlight how turf managers possess the ability to alter the carbon footprint of their land.

Since the birth of the planet, the chemical element carbon (C) has played a pivotal role in its evolution. Deposited from comets and asteroids, both organic and inorganic C is recognised to have been a key ingredient for the initiation of life on Earth; this underpinned by the fact that it is a building block for 95% of the compounds known to man[¹]. Derived from the Latin word carbo, meaning coal, C is estimated to make up 0.032% of the Earth's crust and upper mantle[¹] (Fig 1). It is naturally occurring in the atmosphere in the form of carbon-12 (C-12), this ultimately incorporated into the bodies of animals via the primary & secondary consumer food chain. Prolific growth and colonisation of the planet's surface by vascular plants over millennia, leading to huge accumulations and reserves of organic matter (OM). This becoming a resource increasingly utilised by humans, one often referred to as fossil fuels. Its structural complexity and flexibility is unique, making it possible for both some of the hardest and softest materials known to man, such as diamonds and graphite, to emanate from it. No other element has or will exert more influence in shaping the planet that you inhabit (Fig 2).

To start our journey, let's take a closer look at the molecular properties that make C special. C-12 is the most abundant form of inorganic C. It has an atomic number of 6 (6 protons in the nucleus) and an atomic mass of 12 (6 neutrons and 6 electrons), this accounting for the C-12 categorisation (Fig 3). A unique feature of C is its ability to bond with itself, leading to the term 'pattern maker'. This ability allows it to create exceptionally long and resilient chains known as polymers, seen everyday in natural and synthetic forms, including proteins, nylon and plastics. It is capable of making covalent bonds with other organic molecules such as oxygen and nitrogen. These exceptionally strong single, double and treble bonds enable the production of the organic compounds that are present in all living things.

Fig 1: Shungite mineral rock with a carbon content greater than 98% and Fig 2: Global carbon store

On a global context, evolution over millennia has enabled processes, fluxes and exchanges to achieve regulation and equilibrium of the levels of C currently present in soils, oceans and the atmosphere. These providing the foundation for the multitude of life supporting services that humans are dependent on. The production and decomposition of all living material and the subsequent production of OM are a constant addition and subtraction to these C rich reservoirs. Advances in technology and a changing climate has made previously secure stores of C now accessible. OM newly exposed to its nemesis oxygen, resulting in accelerated rates of decomposition. The greatest depths of the oceans are a resting place for huge accumulations of carbonates, these now threatened by warming waters. Onset of the industrial age and the growth of the human population has placed pressure on the natural world's C equilibrium. Anthropogenic inputs from industry, as well as land change driven by agriculture and urbanisation, has had a destabilising impact. Simply put, more C is being produced than the planet's buffering mechanisms can absorb (Fig 4).

Why should increased levels of atmospheric C be of concern? A term that I am sure you will be familiar with is that of greenhouse gases (GHG). C plays a prevalent role in two of these, carbon dioxide (CO₂) and methane (CH₄), with the other perhaps less well known, but equally potent, GHG being nitrous oxide (N₂O) (Fig 5). The presence of these gases at increasing levels in the atmosphere has an insulating affect on the planet, preventing heat rebounding from the Earth's surface from escaping. Think of the stratosphere layer of the atmosphere as a large porous umbrella covering the planet, with the permeability of the umbrella reducing as concentrations of GHG increase. This subsequently leading to a warming of atmospheric temperature, hence the term 'global warming'. The scale of this issue emphasised by the fact that estimated atmospheric CO₂ levels in 1860 were 260ppm, while in 2018 they were 407ppm[²]. An increase of 64%.

Fig 3: Atomic structure of inorganic C-12 and Fig 5: Molecular structure of recognised greenhouse gases

Let's now concentrate on an area that I hope is of particular relevance to the majority of readers, the relationship between C and turf management. The physiology of vascular plants, including grass, is ultimately geared towards a few relatively simplistic goals. These being the capture of light, regulation of water uptake and loss, defence against pests & disease, reproduction, and the fixation of C from the atmosphere. The process of photosynthesis enables our planet to create and support life via the conversion of solar energy into organic carbohydrates. Possessing the capacity to fix C is pivotal to achieve this. Exposed to changing biotic pressures, plants have evolved specific mechanisms to achieve maximum efficiency in this area.

The most common method utilised is referred to as C3, with the stomata able to fix C during daylight hours, with the insertion of two 3 C molecules into the Calvin cycle (Fig 6). An alternative C4 method meanwhile provides the plant with extra protection from water loss resulting from photorespiration. This is achieved by incorporating the location of the Calvin cycle in bundle sheath cells, in this instance, a 4 C molecule is produced. The final method is referred to as CAM (Crassulacean Acid Metabolism), this being most common in arid conditions where water loss must be kept to an absolute minimum to enable survival. This method allows for the fixation of C during night hours, enabling the stomata to remain closed during the day (Fig 7).

Whichever method is employed, the objective is the same, to allow for the fixation of these all important atmospheric C molecules and subsequent insertion in to the Calvin cycle. Management practices that maintain stomatal health, particularly during times of increased stress, will be the most successful in aiding the grass plant to achieve this. Differing methods of C fixation are examples of plant evolutionary change over millennia in response to climatic pressures. In recent decades, biologists have increasingly observed such changes, with one example of this being a decrease in stomatal density in response to elevated atmospheric CO2 levels. It may seem obvious to assume that an increase in the availability of CO₂ would be beneficial to plants, but the contrary is actually true, with research indicating that once concentration reaches 1000ppm, photosynthesis is in many cases impeded[3]. This referred to as CO₂ saturation.

Fig 4: Global carbon cycle

Moving the focus of attention below ground, it soon becomes apparent the magnitude of the role that C plays in a functioning growing medium. As noted, photosynthesis enables the conversion of inorganic atmospheric C into organic carbohydrates. A proportion of these are deposited via exudates into the area surrounding root tips, this referred to as the rhizosphere. These providing a source of energy for the microbial community which inhabit this region. The utilisation of these C rich deposits is exemplified by the fact that the average C:N ratio of a soils total microbial biomass is believed to range from 4:1 to 8:1[²]. The plant - biota C relationship is very much a mutualistic one. Mucus and discharge from biota act as cohesive binding agents for soil particles, enabling the formation of aggregates (Fig 8). The macro & micro pores that these aggregates provide ensuring porosity, and subsequently the availability of oxygen and water to plant roots. Meanwhile, vast networks of mycorrhizae fungi are eager to exchange nutrients and water with plants for C rich compounds. These all crucial components to achieving a healthy soil structure.

Availability of C compounds in the soil matrix is also an essential building block to enable the process of decomposition. Even the most resistant of OM such as cellulose and lignin is ultimately decomposed by specialist fungi and bacteria. However, when oxygen limiting conditions prevail inhibiting decomposition, resistant OM can result in stable soil C pools persisting for thousands of years. The decomposition process that occurs in a functioning soil is fundamental for achieving equilibrium in the C cycle, with the vast amounts of CO₂ released by respiring biota an essential input. Ultimately, this can be recognised as contributing to the restocking of the atmospheric C pool for your grass to utilise. These types of feedback loops are a regular occurrence in the natural world. Soil conditions, particularly water levels, will impact these and the compounds omitted. Saturation of a soil profile results in denitrification through anaerobic bacteria, with a bi product of this being N₂O. Meanwhile, CH₄ is produced from microbes via a process known as methanogenesis (Fig 9). This highlighting the complexity of the relationship that exists between land management and GHG omissions.

Fig 6: Calvin cycle phases and Fig 7: The physiology of a monocot leaf such as grass

The field of agriculture is increasingly recognising the benefits to be gained from maintaining levels of C within soil. Modern methods increasingly focus on organic materials, cover crops, crop rotation, and reduced disturbance of the land, by avoiding aggressive maintenance practices. In doing this, farmers are able to harness the benefits of the suns solar power through maximising the input of root exudates. Thus maintaining the health of their soils and increasing the net primary productivity (NPP) of the land. Leading to the term 'light farming' (Fig 10).

Practical decisions taken on a daily basis will ultimately determine how the C footprint of your land is regulated (Fig 11). Feedbacks will vary from the obvious to the more discreet, where your impact is perhaps less appreciated. Keystone blocks in your maintenance programme such as nutrition, irrigation and the consumption of aggregates are all of relevance. An increasing industry emphasis placed on a biological approach to nutrition recognises the importance of maintaining the biological capacity of a growing medium. Whether through the use of compost tees, bio-stimulants, or via the incorporation of a topdressing material with a suitable OM content, maintaining a consistent input of C should be a primary objective. This helping to avoid the pitfalls of an over reliance on synthetics. Additionally, this reduction in use and resulting demand for synthetic fertilisers helping to counter the high C cost of their production. The industrial process in question, which enables the fixation of atmospheric nitrogen to ammonia, is known as the Haber-Bosch process, and is believed to consume more than 1% of the world's total energy consumption[⁴].

Fig 8: Carbon rich root exudates enhance aggregate formation and Fig 10: Cover crops used to replenish soil carbon levels

Benefits to be gained through astute irrigation management may be an area that is less obvious. Evolving technology is providing land managers with an increasing armoury at their disposal for monitoring soil moisture levels, providing the greater transparency that comes with the collation of data. Utilised fully through precision targeting, energy consumption can be minimised by way of streamlined run times and reduced pumping requirements. Consumption of aggregates, whether this be sand, gravel, or divot mix, come with a C cost. While recognising the use of these are a requirement for many maintenance practices, does the option to resource them more sustainably exist? The recycling of on course materials for the production of top soil and divot mix is a practice employed by a number of golf courses. This often providing a material with a higher nutritional and biological value, along with a saving to your budget. It must be recognised that the extraction, processing, and carriage of aggregates does have an impact, even if this impact is out of sight. A commitment to minimise this where possible, by thinking outside the conventional, will bring with it long term benefits closer to home.

As previously touched upon, natural C fluxes constantly occur in land management. The opportunity to impact these exists through the implementation of responsible woodland management, re-wilding and rough grass land management programmes. This can be achieved through the re-establishment of native species, perennial grasses, and increased bio-diversity. Harnessing stakeholder understanding and participation, be this member or public, will be key to ensuring long term success for these types of land reforms. Resource consumption is also relevant in areas directly away from land management. For many businesses this will specifically apply to energy, waste and catering. Recent evolution and affordability of renewables has made improved efficiency in the first two areas increasingly accessible and attractive to many. For the latter, by ensuring catering supply chains are local and maximising 'in house' productivity, positive changes are achievable. All bringing with them financial incentives as well as a positive C trade off.

Fig 9: Drainage efficiency impacts emissions of CH4 and N2O gasses

The background to writing this article has been that of a global pandemic. It has brought with it changes and challenges that none of us ever expected to experience. The fallout is uncertain, with the long term financial cost to society and sectors of industry unpredictable. However, history has shown that in the face of adversity of such magnitude opportunity can arise. The chance to re-set, re-think, and re-route our direction of travel. To be big, bold, and brave in our decision making, enabling change and regeneration. Lockdown has brought many people closer to nature, awakening a greater appreciation in the importance and value of the natural world. This coming November, the 26th UN Climate Change Conference will take place in Glasgow. An opportunity for countries to evaluate and commit to action with the aim of achieving set 2030 global carbon emission targets. These, to the outside person, can seem very abstract. How can 'my' actions, 'my' business, or 'my' industry really have any impact on such a global context. The reality however is that these targets can ONLY be achieved through action at a granular scale. Through individual responsibility evolving in to collective responsibility. Community action creating societal change.

The turf industry is a prime example of this. YOUR actions on a daily, weekly, and monthly basis help shape the carbon footprint of the land you manage. By embracing this responsibility, your rewards can be multifaceted. Financial, ecological, biological, industry recognition, public perception, product value, customer experience, sustainability, robustness, to name but a few. Not losing sight either of the benefit, understandably perhaps of greatest importance to many turf managers, that of enhanced turf quality and performance through improved soil health.

Fig 11: Overlapping carbon footprint of a land management business and Right: Derek Fullerton

The actions or inaction of the current generation will impact the well being of future generations. The knowledge base and technology exists for us as an industry to play its part, accept its responsibility, firmly anchoring its seat at the table. Through empowering young turf professionals with a greater insight and understanding of the key elements and processes related to turf management, progress will be accelerated and with it the industries contribution and long term prosperity. I sincerely hope that this article has provided you with a greater insight into one of those elements and its influence on your profession. The father of them all, carbon.

Article by Derek Fullerton BSc (Hons) Murrayfield Golf Club Edinburgh

Derek is currently undertaking Post Graduate study at the University College Dublin in Environmental Sustainability.

Citations

[¹] Pappas, S. (2017) Livescience.com
[²] Horwath, J. (2007) Soil Microbiology, Ecology, And Biochemistry
[³] Zheng, Y. (2018) BMC Plant Biology
[⁴] Cherkasov, N A. (2015) Chemical Engineering and Processing 90 (2015) 24-33