The carrying capacity of a pitch is a statement of the sustainability of maximum usage that does not cause an unacceptable reduction in the playing quality of the pitch.
[Note: Sustainability is a contested and interesting concept to explore in its own right. This is a frequently overused and misused term within the turf and grounds care industry.]
We all want to play on a football pitch which is of a good quality, but there will be times when it isn’t wise to play a game, either for safety reasons (such as when it is too hard, or it’s frozen) or when it is too wet and playing on it will damage the soil structure and the surface will be kicked out more easily.
By having an understanding of carrying capacity and pitch playability we can make much better use of available resources, spend money more wisely and also reflect on how to better look after a pitch if we want to have a surface that is going to last all, or most, of the playing season. We don’t want it to start wearing out before December, so we’ll need to make sure the groundsman or grounds manager responsible for looking after the pitch is able to make sensible decisions as to when a game needs to be postponed, with players and managers respecting the decision made.
We mustn’t forget that the groundsman / grounds manager is trying to produce a suitable surface for an entire season not just for a couple of games. Sometimes, tough, sensible but unpopular decisions need to be taken.
Often a pitch is quoted as having the potential carrying capacity of (let us say) 70 games. Dividing the entire playing season’s carrying capacity in hours or games of use into weekly figures provides a helpful guide to potential average weekly usage. In this example it would be 2 (adult) games per week.
During some parts of the season, such as during September and early October (going into November in milder climate regions), the actual usage that can be sustained on a pitch can be greater than the average carrying capacity for that period of time. So for example, we might find that we can get 3 games per week for several weeks without causing undue wear and tear during September and October.
The reason for this is that natural grass growth and recovery, at that time of year, can partly compensate for the increased usage. At other times it can be less than the average due to poor weather. Consideration needs to be given to managing usage of the pitches based not only on the estimated carrying capacity, but also the current weather and ground conditions.
Making use of current web technologies I’ve created an online combined carrying capacity and pitch playability model which demonstrates how a range of variables can influence not just the overall carrying capacity but also the daily / weekly playability of a football pitch.
Some of the data are taken from historic research whilst I’ve provided a guestimate for others to help demonstrate the concept. Hopefully the model will help people involved in managing a football pitch to better reflect on the activities they carry out and especially how the user is managed.
Carrying capacity model
In the carrying capacity part of the model I’ve included the following features which act as variables to consider:
- Your pitch construction
- Existing drainage conditions
- Length of the growing season
- Annual rainfall
- Nitrogen applications
- Sand applications
- User expectations (i.e. Performance Quality Standards level)
- Education & training.
Pitch playability model
For the pitch playability part of the model I’ve introduced a ‘Pitch Playability Rating’, from 0 – 4+. Essentially what I am trying to show here is the answer to probably the main question any player or team manager wants answering, “What is the likelihood that our game will need to be postponed or cancelled due to the current pitch ground conditions?”
Adjusting the variables will produce a rating of either:
- 0 = unplayable
- 1 = play not recommended
- 2 = playable: limited playing experience
- 3 = playable: satisfactory playing experience
- 4+ = playable: good playing experience.
[Note: Initially I thought of a 0 – 10 rating, but found this overly complicated. The 0 – 4+ probably provides the answers players / managers would want anyway. I’ve added the + to the 4 as I haven’t run through all the scenarios, but expect the top figure to be 4, so have just added the + in case the coded maths throws up an anomaly!]
In this part of the model I’ve considered the statement provided in some helpful documentation by Sport England of, “The playability of pitches depends upon a combination of prevailing weather conditions, physical characteristics of the soil profile and the standard of management provided.”
‘Natural Turf for Sport’, (2011) Sport England, p.27
I’ve therefore included the following features which act as variables:
- Your pitch construction
- Existing drainage conditions
- Total ground cover
- Main root growth
- Surface evenness
- Pitch hardness
- Recent rainfall
- Surface water
- Active grass growth
You will notice that there are two core features in each part of the model. I consider these the core components for each requirement of the model. I could also include features from each part within the other part of the models as well, but for ease of working out a reasonable equation for each for the time being the included features allow an adequate range for informed demonstration purposes.
I’ve created what I think is a useful snap shot of results to illustrate carrying capacity data, playability as well as some maintenance data: all from a simple user interaction of selecting a few options.
[Note: The maintenance data are not meant as being realistic – they are just data put into the behind the scenes coding to ensure the calculations work. Accurate data can come at a later date]
Being able to readily develop such models with available web technologies can help ground staff and others better understand the consequences of their actions. At the end of the day we all want to make best use of our, often limited, resources. Hopefully this model helps a little towards that aim. Enjoy.
Chris Gray: November 27, 2016