Managing carrying capacities

Why identify the carrying capacity of a turfgrass surface?
To assist in the effective and sustainable management of a turfgrass surface it is not just good practice, but actually essential, to identify the likely carrying capacity of a turfgrass surface, especially sports turf surfaces.

How many turf or facility managers have determined their carrying capacity? How many have not tried? How many are not bothered? If carrying capacity has not been estimated or determined then now is the time to reflect on this and find out more, but it can’t just be ignored if we are to manage turfgrass surfaces in a professional way.

By understanding the carrying capacity, managers will be able to make informed decisions for optimum maintenance and management requirements, so as to deliver a surface that is sustainable, especially regards the consistency of playing experience. It will also enable stakeholders, who will have access to better information, to contribute more positively to decisions that affect turfgrass surfaces, allowing them to have a greater affinity to ‘their surface’.

Football on natural turf

Football on natural turf

Managing the user of a turf surface is an important role within turf management and this should be reflected in the use of policies such as for match cancellations, diverting usage from areas or closing off some areas.

Carrying capacities of turfgrass surfaces
There are a range of criteria that can influence the carrying capacity of a turfgrass surface; these are often related in a complex manner, which can complicate the decision making process, but which can be more readily addressed by taking a systems approach to management.

Carrying capacity may be modified and influenced by a range of factors:

  • having a lighter soil texture and crumb structure;
  • increasing and maintaining a dense ground cover;
  • root growth – increasing depth and root mass throughout a soil profile;
  • increasing the ability of the rootzone / soil to remove surface and sub-surface water (e.g. drainage capacity);
  • healthy soil ecosystem (encourage a good soil structure; optimum plant growing conditions);
  • weather and micro-climate: e.g. temperature, rainfall, shade, relative humidity;
  • local topography; e.g. sloping ground, low lying lands potential to flooding etc.;
  • management strategies (e.g. pitch cancellation policy; active diversion policies to spread wear; stakeholder involvement to better understand effective pitch management; active management of users/usage);
  • maintenance inputs (e.g. staff, equipment, materials);
  • skills and competence (education, training, ongoing personal development through CPD programmes) of staff;
  • technological enhancements, e.g. inclusion of synthetic materials in the rootzone; water extraction pumps, which can all help to increase the potential activities or usage of surfaces;
  • technological innovations, e.g. the use of lighting rigs to encourage strong growth to develop a hard wearing surface (not soft easily worn growth) where shade conditions exist.

The carrying capacity of a turfgrass surface is a helpful, informed, guide to the level of use that might occur, although because of natural variability, such as extreme or inclement weather conditions and especially the management of the user there will be a variance from any initial estimate. For example, playing a football match in very wet conditions will considerably increase divoting and overall wear on a pitch, resulting in a much-reduced carrying capacity. The type (e.g. age group, intensity of use) and pattern of usage (e.g. mostly at weekends, concentrated / staggered / spaced out periods of use) will also affect the actual carrying capacity.

The carrying capacity of a turf surface is typically expressed by the type of use or activity that occurs. For example, for a football pitch this would be in games or hours per unit of time (week or season), for golf this may be per rounds per year, whilst for a parkland this could be number of users per week / season.

It might be useful to think of carrying capacity as having two different perspectives: Effective (or Potential) and Actual.

Effective carrying capacity will be what could be achieved given optimum use and management strategies being implemented and is more of a forecast as to what could realistically be achieved.

Actual carrying capacity is looking back over what has been achieved and may vary from the effective carrying capacity due to how use and management strategies have actually been implemented in practice.

So, ‘What’s your carrying capacity?

Carrying capacity and pitch playability model

Carrying capacity and pitch playability model

I’ve blogged another article about carrying capacity which also includes an interactive carrying capacity model at Carrying Capacity v Playability, so check that out as well.

Chris Gray, 14th February 2017