The Groundsman

December 2014

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TECHNICAL UPDATE 23 the Groundsman December 2014 Visit for more information and digital editions Robert Donald CEnv MIAgrE is managing director of Twyford Twenty, which undertakes a range of consultancy activities including drainage design within sports field construction, cemetery development and landscape industries. Before that he was managing director (1996- 2011) of White Horse Contractors, a specialist contractor focusing on the construction of natural and synthetic sports playing surfaces, and from 1993 to 1996, was project manager at specialist sports pitch and golf course constructor, M J Abbott. Robert can be contacted by phone – 0780 352 6379 – or email: About the Author Imagine the benefit of being able to measure and record stored atmospheric carbon dioxide as a carbon compound within the soils of a permanent grassland area: carbon offsets, carbon credits, carbon audits and carbon trading - all contributing to the desirable 'low carbon economy'. Consider a grass plant rather like an iceberg. The grass plant biomass comprises about one part above ground, grass leaves (the sward) and four parts beneath ground, in the extensive root system. As long as that status quo is maintained and those permanent managed urban green infrastructure areas are left undisturbed, the soil organic matter within those public green spaces increases incrementally for decades. Having identified the benefits of incorporating 'carbon grasses' within the national green infrastructure, how can this be implemented practically? The answer is 'sward swap', a non-destructive and discreet method of exchanging grass cultivars over a given area to introduce carbon grasses. No ploughing or cultivation is required, nor is surface disturbance. Spray off the existing sward (systemic non-residual herbicide) and immediately follow with intensive overseeding of carbon grass cultivars. As the existing sward dies, the new cultivars germinate and grow within the dying sward providing an indecipherable transition from old sward to new. The dying sward takes seven/eight days after herbicide application to demonstrate discolouration as it dies off, which conveniently correlates with the germination period for the new grasses coming through. The old sward provides a physical biological protective germination barrier to the new sward. Once the new sward has reached a height of approximately 30mm, ongoing mowing maintenance may resume in order to help develop the sward and create dense grass covering. It's so simple it's just got to work, and my field trials of the process have provided encouraging feedback. What of the cost? It's easy to argue that the reduced maintenance costs, mowing fertiliser and irrigation easily cover the sward swap process. Being a realist, carbon grasses and sward swap are not the 'silver bullet' solution to climate change. There's certainly more to life than grass. But it's a good place to start. Robert's 'Unlock the secrets of the soil' presentation was one of a number of presentations made at The Sustainable Green Infrastructure Conference organised by Green Social Engineering. The conference presentations make interesting reading for groundsmen, and seminar slides/videos are accessible at: l The development of carbon grasses In 2009, Robert was contracted to build natural turf sports facilities in both the United Arab Emirates (arid desert climate) and Brunei, Asia (humid tropical climate), projects that, he says, challenged his grass knowledge which was largely based on temperate season perennial grasses for sport and amenity usage. He met with the grass scientists at Top Green's grass science station in France and discovered the "fascinating detail of the company's 16-year grass breeding programme, where thousands of different grass cultivars are crossbred to create hybrids demonstrating the most desirable qualities for the grass seed market". Robert says: "Deep rooted varieties are always considered advantageous for reasons of plant health, nutrient uptake, drought resilience and overall sward toughness and durability. Part of this investigation into deep rooting varieties involved the study of soil organic matter contribution, derived from the seasonal 'shedding' of the microscopic adventurous root fibres (villi). The 'propagation' of these root fibres significantly added to the soil organic content and also provided a food source (glucose) to the microbiological fauna inhabiting the soil matrix. "I came away from the research station with a whole new understanding about the contribution that temperate season perennial grasses can make to bio sequestration rates and soil structure forming initiatives, and I subsequently worked [with Howard Wood, director, Landscape & Sustainable Services] to produce a list of cultivars with specific applications in green infrastructure environments and dubbed these cultivars as carbon grasses, which are mostly comprised rye and bent grasses, and creeping fescues." CARBON GRASS T - heralding a paradigm shift in the efficiencies of grass regimes. Slow growing cultivars enable significant 40%+ cost savings. Deeper roots enable 300% more carbon sequestration

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