Giving turf a sporting chance
By Jayne Leyland
Barenbrug's Jayne Leyland looks at the influences on grass seed
selection for heavy duty sports pitches
The expectations of natural grass sports surface performance has increased dramatically in recent years. In anticipation, grass seed breeders continually strive to produce cultivars with significantly improved desirable characteristics in both traditional and unique species that have the capability to perform in these demanding situations. We at Barenbrug are committed to maintaining the preferred position of natural grass surfaces!
Seed cultivar and mixture selection really can have a significant impact on the overall quality and performance of the playing surface. However, sometimes choice (especially species selection) can be severely limited, primarily because of the available time for the establishment of the sward prior to play. Because different grass species have different germination and establishment capabilities at different soil temperatures, it is most often the case that the fast-germinating/establishing perennial ryegrass is the only choice for renovation. The choice of species is considerably widened for new constructions. Let's take a look at how this impacts on our mixture selection for stadia and open field pitches for both renovation and construction.
Enclosed sports stadia pitches are not the natural ideal environment for growing perennial ryegrass. Despite its hard wearing performance capabilities, the combination of poor light levels, high humidity and low nutrient availability - due to the poor cation exchange capacity of the heavily irrigated, predominantly sand-based rootzones - means the ever-hungry ryegrass is permanently under stress, even without wear. If renovation time is limited to less than 10-12 weeks there are currently two choices available, either use 100 per cent perennial ryegrass for overseeding, or re-turf with a mixture of species that have the natural potential for improved performance in these conditions.
Barenbrug Research is currently undertaking extensive trials for combined shade and wear performance, not only for individual cultivars within species but, importantly, for mixtures. The results and information from these recent and on-going trials are being used to influence mixture formulation. Recently introduced and potentially new cultivars of all species plus 16 different mixture combinations were trialled over a 12-month period in a shade tent (65 per cent Photosynthetic Active Radiation (PAR) reduction) with average humidity 10 per cent (to a maximum 100 per cent) higher than outside the tent. Synthesised wear was applied weekly from November 2004 until the end of April 2005, five months after sowing (to enable inclusion of slower-establishing species) at the equivalent of four consecutive matches per wear application. The trial will continue each year with the introduction of new cultivars and reformulated mixtures.
Mixtures 1 and 2 show the excellent performance achieved with the use of innovative species, allowing for adequate establishment time. Mixtures 3 and 4 are more commonly used for stadium pitches either as seed or turf.
The results revealed that innovative species can offer improved performance in these conditions. Although these slower-establishing species may not be considered as a choice for overseeding for short renovation windows, they can be either custom grown as turf for renovation (available from accredited growers) or used in a seed mixture for new constructions. Rooting depth capability is important for stabilisation and for healthy plant growth, but root mass near the surface is also important to minimise divoting and scars. Tall fescue has a deep rooting capability and is naturally more adapted to growing in these conditions. RTF (rhizomatous tall fescue) also has the added value of producing rhizomes for both recovery and tensile strength. Tufted hairgrass is naturally adapted to shade and has the capability of producing a very dense root system.
Individual cultivars within a species also exhibit significant differences, in this instance perennial ryegrass.
For perennial ryegrass, the trial also demonstrates that in addition to the characteristic of excellent wear tolerance it's also essential to identify those cultivars which can perform in combined shade and wear. It is important to consider that a 'highly rated' cultivar for wear in the open field may not necessarily perform in a combined shade and wear situation, while a 'lower rated' open field cultivar may offer superior performance in combined shade and wear situations.
The trial also highlighted that cultivars which are more susceptible to leaf spot are the ones with poorer performance in this trial. There were also seasonal variations, with some cultivars performing better in the winter months and others with faster spring recovery. Perennial ryegrass as a monoculture succumbed more to leaf spot than other species in the trial, for example tall fescue (festuca arundinacea) and tufted hairgrass (deschampsia caespitosa), resulting in a thinning sward which is much more susceptible to poa annua invasion.
The introduction of artificial lighting systems has also been seen to support growth in these difficult conditions, and by selecting species which can better perform naturally in shade there is the potential to reduce the cost of operating these systems.
Open Field Pitches
The main barriers to achieving successful results when overseeding open field pitches are compaction, the unavailability of overseeding equipment to sow the seed at the optimum depth, too short (or a non-existent) establishment window and either too much or too little natural precipitation. As most heavy duty sports pitch renovation is carried out in May or June, the soil temperatures are usually sufficient for very successful germination of perennial ryegrasses and red fescues, provided there is sufficient water available to the plant and the seed is sown at the correct depth.
Because of excellent wear tolerance and short establishment windows, the most commonly used renovation mixture is 100 per cent perennial ryegrass. The main problems with this choice are a resulting open sward and a higher risk of disease. Although ryegrass looks dense at the sward surface, it can be very open at the base of the sward - even cultivars with higher shoot density. This could mean potential instability at the surface (increased divots and scars) and it could also provide an opportunity for poa annua and other weed ingression.
Monocultures are generally more susceptible to disease, which will cause still more rapid thinning of the sward. The low input regimes typically associated with many open field pitches (particularly local authorities because of budgetary constraints) means the grass is continuously under stress.
What are your key performance criteria when choosing a blend of perennial ryegrasses? If you can apply little or no fertiliser, consider ryegrasses which can perform with lower nutrient inputs. If recovery after wear is one of your key characteristic requirements, there are cultivars of perennial ryegrass available (such as Romance) which offer improved shoot recovery and therefore sward density.
Some mixtures are formulated to include other species such as red fescues to give a base to the sward and improve overall drought tolerance and disease resistance. These can be successfully used where a little more establishment time is possible. Perennial ryegrasses and red fescues can co-habit in a low nutrient input sward, provided the initial formulation of the mixture does not permit the aggressive ryegrass to completely out-compete the fescue. Cultivar selection for this type of mixture is extremely important, for example, you may choose a less aggressive ryegrass to allow the fescue opportunity to establish.
Smooth-stalked meadowgrass offers excellent recovery through the ability to produce rhizomes, but both recovery and establishment can be notoriously slow. If you have the opportunity to sow a new construction with a mixture containing smooth-stalked meadowgrass, again, consider your key characteristic requirements. Also remember the sowing depth influence; if the small seed of smooth-stalked meadowgrass is sown too deeply in a mixture with the larger seed of the more aggres
The graph below shows Bartender, a new smooth-stalked meadowgrass which germinates at cooler soil temperatures.
If there is an adequate renovation window, don't discount tall fescue in this situation for its excellent rooting depth capability and root mass (stabilisation of goalmouths) and lower nutrient input performance. Its ability to produce such an extensive root system gives it great drought tolerance.
Although, for many reasons, perennial ryegrass is still the number one choice, if you have an adequate renovation window, a specific site or maintenance constraint, or are able to use custom grown turf, consider other species. There is almost certainly something there to help you. Whichever species you choose, always consider mixture formulation (species percentages and cultivar characteristics), sowing depths, available establishment window, soil sowing temperatures, mowing heights and frequencies, nutritional inputs, environmental conditions (soil type, precipitation), compaction relief, susceptibility to disease and, of course, wear. All affect the subsequent composition and potential performance of the established sward.
If you would like further information please contact Barenbrug at Rougham Industrial Estate, Rougham, Bury St Edmunds, Suffolk IP30 9ND. Telephone: 01359 272000, fax: 01359 272001, email: firstname.lastname@example.org website: www.barenbrug.co.uk