Sand in turf management

Over the past decade, no other material has taken on such a prevalent role in the management of sports turf than sand. The material is now incorporated into a multitude of maintenance practices, with technology allowing greater volumes to be applied with reduced disruption in condensed time frames.

Fig. 4: Topdressing with a spinning disc spreader

In this article, Derek Fullerton (Murrayfield Golf Club) aims to look at the differing characteristics of this precious material and the practical implications these may have in the management of your turf. It also seeks to discuss whether an over reliance on sand may hinder the industry's ability to fulfil its responsibilities in meeting future environmental challenges.

To begin, let's take a closer look at the material itself. Sand is formed by biochemical processes involving both physical disintegration and chemical decomposition over many millennia. Originating from molten magma igneous rocks and sedimentary rocks, which cover about 75% of the Earth's surface, the material you use will most likely have a long and varied history. Where glacial waters were able to flow freely, sediments accumulated in valleys and plains, whilst minerals were carried away. When exposed to calcium or iron in the water, quartz sand weathered from igneous rocks such as granite, cemented to form solid masses known as sandstone. As in the case of sand dunes, wind was a natural vehicle to transport material over vast distances. By whatever means the sand that you use arrived at its destination, there is a good chance it began its formation in a very different geographical location.

The destructive nature of weathering plays a key role in regulating the size, shape and uniformity of the material, with the origins of the parent material influencing its chemical composition. To be classified as sand it must fall within a size range between 0.063mm-2mm. Grains originating from glacial and transported material tend to be more rounded and uniform in shape, with those originating from residual sandstone deposits more angular and irregular (Fig. 1); all characteristics that are key to how your sand functions.

Left: Derek Fullerton BSc (Hons) Right: Fig. 1: Microscopic image of sand particles

Sand for industrial use is mainly sourced through three forms of extraction, these being mines, quarries and river bed dredging. For it to be suitable for use in sports turf, 'hydro classification' washing removes impurities whilst also allowing the material to be separated into grades depending on size category. This process enables companies to provide products that meet specific particle size distribution (PSD) criteria.

Technology has provided turf managers with the means of incorporating increased volumes of sand into their maintenance programmes. Examples of this include Graden and Dry Ject sand injection practices (Figs. 2 and 3), these allowing for the removal of organic matter (OM) whilst incorporating sand into various depths of the profile. More efficient disc spreaders (Fig. 4) and brushes also allow for higher quantities to be applied through top dressing, whilst techniques such as sand banding are often used to address drainage issues. Whether its addressing problematic OM levels, water retention or surface performance characteristics, sand is often now the 'go to' material.

An example of the integration between sand and technology can be seen at the BT Murrayfield stadium in Edinburgh, the home of Scottish Rugby. Head groundsman Jim Dawson, and his team of five, are responsible for maintaining three turf training pitches and the main stadium Desso Sportsmaster hybrid pitch. The hybrid pitch construction specification is a relatively new technology involving the incorporation of synthetic fibres into the natural grass sward, the aim of this being to increase surface stability and sward durability for high impact sports such as rugby and football. The success of this was highlighted by the fact that over the last season BT Murrayfield's hybrid pitch was able to host to up to 75 games, almost a 50% increase on the previous pitch. This increased resilience also allows for the venue to be utilised for concerts and other sporting events, important financial revenue streams.

Left: Fig. 2: Kiln dried sand incorporated into sand injection process Right: Fig. 3: Graden sand injection practice

The yearly maintenance programme consists of the top 8-15mm of the pitch being removed with only the synthetic fibres remaining, these having a life span of roughly 8 years (Fig. 5). On average, 90 tonnes of Leavenseat LV25 sand are then applied whilst a specialist machine creates a seed bed for overseeding (Fig. 6). The annual removal of this top layer is crucial in the success of a pitch of this nature, in part due to the inert nature of sand. The sand provides the perfect environment for transmitting surface water and allowing initial strong root development, but at a cost. The pitch is thirsty and nutrient hungry, with slow decomposition of OM, this being quick to accumulate due to the top growth required for high performance pitches. If allowed to go unchecked over a period of time, pitch performance would soon be impaired.

One practice implemented by Jim to help negate the sterile nature of sand is in the use of compost teas. These liquid 'brews' are a source of highly valuable microbes that constitutes the microbial community that enables a growing medium to support life. Be this decomposition, nutrient recycling or pathogen suppression, soil microbes are at the heart of it all. Increasing the volume of sand in your growing medium will make it a more hostile environment for microbes to inhabit. This area is of particular relevance to Jim and the team due to previous experience of the pitch performance being detrimentally affected by root eating nematodes. The use of bio controls such as compost teas can help maintain equilibrium in the soil food web and act as a preventative measure against such issues.

Fig. 5: Synthetic fibres remain following sward removal

The hybrid pitch specification and subsequent maintenance requirements is a costly investment, but in the case of BT Murrayfield the investment is an astute one due to the enhanced pitch performance and additional income generated. The properties of sand play a crucial role in the success of this modern concept, but care must be taken to avoid the pitfalls of creating a sterile growing environment.

Sand also plays an integral role in the maintenance programme of Scott Corrigan, course manager of Cawder Golf Club in the west of Scotland. Utilising the material in practices such as sand injection, deep veemo slitting and post coring top dressing has allowed Scott to refine surface playing performance, aid the movement of water in the upper profile and re-establish surfaces following disruptive maintenance practices. Annual target rates range from 100-120 tonnes, with Leavenseat LV20 one of the products previously used.

Over time, Scott has come to recognise the additional pressures, both financial and agronomical, that high inputs of sand can have. Wear and tear on machinery and cutting units can put pressure on budgets, particularly when in-house grinding is not an option. High annual application targets can eat into labour demands when staffing numbers are limited. From an agronomy point, the potential adverse impact that high application rates can have on disease pressure is one that Scott gives careful consideration to. Reduced available leaf blade exposure to sunlight, surface pH fluctuations and uneven leaf blade incision from blunt cutting units will all contribute to putting the grass plant under increased stress, making it less able to fend off attacks from harmful pathogens.

Fig. 6: Overseeding following application of LV25 sand

Material cost and consistency is also an area Scott believes to be problematic. With the abundance of sand reducing globally, whilst demand and carriage costs increase, these issues will only continue to manifest themselves in an upward trajectory, one which is outwith your control. Scott also includes a biological element as part of his maintenance programme. As well as the addition of organic acids such as humic and fulvic acids, compost teas are applied monthly over a ten month period. This again being an example of biological inputs playing a pivotal role.

The use of the Leavenseat LV20 and LV25 by Scott and Jim provides a good opportunity to quickly highlight the relevance that PSD can have depending on the objective. Due to the fact that the top layer of the profile at BT Murrayfield is being replaced on an annual basis, Jim has less concerns regarding the migration of fine particles over time. As can be seen in Fig. 7, the LV25 has a more uniform PSD with 35.9% falling within the fine/very fine category compared to 17.3% of the LV20. Whilst the coarseness of the LV20 may bring with it some issues for Scott in respect of working the topdressing into the sward and wear on cutting units, it minimizes the potential of 'capping' issues in the profile. This situation occurs when fine particles 'interpack' and 'bridge' the pore spaces created by coarser particles, this hindering the free movement of water. If allowed to develop over a period of time due to incompatible rootzone/topdressing materials, this can have drastic consequences on turf performance, particularly in golf greens. The use of material PSD data sheets and 'D' value graphs should always be used to guard against this.

You may well have noticed a common thread forming in the article with regards sand and soil biology. The dependable attributes that make sand beneficial can also prove to be problematic in a growing medium, with its simplicity and inert nature being both an asset and a liability. An area I will attempt to expand on next.

Fig. 7: LV20 & LV25 sand PSD graphs

When evaluating any growing medium, it is important to recognise it as a living entity, a continually evolving dynamic of inputs and outputs, nutrients and energy, providing you with a foundation to manipulate for your individual requirements. The value of aggregate formation is now increasingly recognised in the agriculture sector for maintaining the long term health of a soil. The macro and micro pores that are created by soil aggregates are recognised as the biological reactors for the multitude of microbial processes that underpin the health of a soil (Fig. 8). Agriculture has learned the hard way, with an over reliance on synthetic fertilisers for crop nutrition resulting in infertile soils lacking in OM and structure, which are prone to erosion.

This shift in mindset has led to a term referred to as 'light farming', which recognises the benefits of harnessing the energy of solar radiation through photosynthesis. This approach enables atmospheric Carbon (C) to be incorporated into the biomass of plant material through the process of fixation. Increased emphasis on organic nutrient inputs (slurry, crop residues, legume cover crops, rotation cycles) has enhanced subsequent soil C levels through OM decomposition and liquid C root exudates. This availability of organic C is a source of energy to soil microbes and crucial to particle bonding, allowing aggregate formation.

Can the turf industry learn from agriculture?

Well, something similar is already possible through utilising biological programmes. This allows for the manipulation of soil microbes and the humification of OM (Fig. 9), with this expediting the conversion of organic nutrients (thatch) into plant available inorganic form. This source of organic nutrients is always available to you, creating the correct environment for it to be utilised is key. Excessive levels of sand in your soil profile may well inhibit the development of the biological community you are dependent on (Fig. 10).

Figs 8, 9 and 10

With the government recently committing the UK to achieving a net zero Carbon balance by 2050, all sectors will inevitably come under increased pressure to implement change. Rightly or wrongly, the turf industry and in particular golf has been seen as one of consumption, often leaving a large environmental footprint. Moving forward, does the continued reliance on a finite material such as sand help to address this image? And does it help to robustly position clubs and facilities to withstand future pressures, be these financial or legislatively, that are inevitably coming their way?

The conversation relating to how the turf sector is meeting its environmental responsibilities requires and deserves far greater scope than this article provides. However, it is fairly self-evident that the continued consumption of any material in large volumes, that often requires carriage over large distances, will not aid in reducing an organisation's Carbon footprint. Regulating inputs of external consumable materials to sustainable levels whilst maintaining playing performance levels must be the long term goal. At times, the balance may not be easy to achieve, but in doing so the industry can position itself and its stakeholders on a path that is more aligned to that of other forward thinking sectors.

So to summarize, sand does and will continue to play an important role in turf management. From enabling the utilisation of cutting edge technology to produce high quality pitches (Fig. 11) to refining surface playing performance attributes, the value of sand is undeniable. In recognising its weaknesses as well as its strengths, you will utilise the material to its maximum. Excessive use over time will only aid in creating a biologically sterile growing environment.

Fig. 11: BT Murrayfield stadium

The incorporation of biological and organic inputs into your maintenance programme can help maintain equilibrium, one which allows you to harness the benefits of biological processes that have been the foundation of growing mediums throughout the evolution of the planet. At a time when the public's awareness in the value of our natural world is growing and consequences of its degradation more widely understood,

it is in the industry's own interest to adapt and take a holistic approach to environmental stewardship. By utilising sand at a sustainable level, not only will it assist you in meeting your objectives, you will also be making your contribution to safeguarding the environment. One which will hopefully preserve this precious resource for future generations.

Thank you to Jim Dawson at Scottish Rugby and Scott Corrigan at Cawder Golf Club for their assistance in researching this article.

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