Module 6:

6.3 Soil science

6.3.4 What are the different soil types?

General soil groupings

1   Light

We will now look at how each of our general soil groupings might influence the playability of a football pitch.

Sandy soils can drain well and provide a drier surface, allowing for more games to be played and making it easier (in some ways) to have a better-quality pitch. However, if they become compacted then their benefits can diminish significantly. It’s important to keep these soils well aerated and decompacted to make the most of them. These are the types of soils that are wanted for winter games pitches to help remove rainfall as quickly as possible so that games can go ahead and not be cancelled due to wet or waterlogged conditions.

A pitch on a sandy soil might be able to provide for maybe up to 55 games for a grade 2 pitch, or up to maybe 75 games for a grade 1 pitch, per season if suitably maintained and if located in drier parts of the UK.

Sandier soils do not hold onto nutrients or water as well as medium or heavier soils, so on a very sandy soil there may be a need for more regular watering and feeding. This doesn’t mean that a greater quantity of fertiliser will be given, just that more frequent with smaller amounts might be needed so that over a year the same quantity has been applied.

With sandy soils drying out quicker than heavier soils, there will be a need for more frequent watering during dry periods, especially from May through to August, when adequate rainfall can be less frequent than is needed for the grass plant to maintain a strong healthy sward.

2   Medium

These are generally loamy soils which can offer reasonable drainage at certain times of the year, however, with play taking place over the wetter periods then these soils will often smear and compact thereby losing much of their natural drainage capability.

These soils are well suited to having secondary drainage installed (such as sand-gravel slits and sand banding) thereby increasing the number of games that can be played over the winter period.

Where games are limited (to say maybe no more than 40 games over the playing season) and are of low intensity, then these soils might be suitable in drier parts of the UK without additional extensive drainage works being needed. However, the consistent quality that can be achieved on these pitch soils will typically be at the lower grades of 1 or 2.

3   Heavy

These have higher percentages of silt and especially clay which hold onto water very well. Unfortunately, this is a major disadvantage over the late autumn and winter months due to the relatively high levels of rainfall that typically occurs.

Whilst it is usually beneficial to carry out a range of maintenance activities on a football pitch over this period, where the soil is fairly wet then it is usually wise to keep any mechanical work to a minimum.

The main reasons for this are that the machinery will compress and compact the soil, reducing drainage rates, whilst the rotating action of wheels or rollers will smear the surface soil producing a seal and cap on the surface, thereby reducing the infiltration rate of any rainfall.

These undesirable wet, compacted and smeared conditions will increase the rate at which the grass will wear out and also the number of divots produced. However, the consistent quality that can be achieved on these pitch soils will typically be no more than an Entry grade 1.

The number of games might be from 20 - 30 games for this level of quality. However, where rainfall is fairly consistently spaced out, the surface may not dry adequately for much of the season and the number of games potentially playable can be minimal.

For pitches on heavier soils, it is also usually a good idea to have a surface layer of 25-30mm built up from sandy top-dressings as this helps provide a drier surface for reasonable periods of time in the winter. This can increase the times when a game can be played without causing unacceptable damage from each game, with maybe up to 30 - 50 games potentially being played at Entry grade 1.

The number of games that might be played on a pitch with a heavier soil, without a sand top, can and will vary considerably. The main influencing factor is that of the regularity and amount of rainfall which affects the wetness of the soil. August to October will often be the most satisfactory period for play, allowing for maybe up to 20 games to be played during that period. Regular and just steady rainfall during this period could effectively exclude the use of the pitch from accommodating games.

From November to the end of the playing season, the additional number of games might typically be from 5 to 15, but the actual number of games that might be played are so heavily dependent on the soil moisture content, when often the pitch doesn’t dry adequately to allow for a suitable game to take place without excessive wear and tear occurring and it quickly turning into a mud-bath.

3   Note on potential games for a soil type

Actual games played can, and typically will, vary considerably from the general figures given above.

It is often challenging and very subjective to provide figures for undrained or pipe-drained pitches without clarifying the influence rainfall frequency and quantity have on trying to plan a games schedule. So, geographical location of a pitch has a significant influence on whether games can often go ahead or not during a playing season.

To improve the consistency and accuracy of forecasting and game planning, there is usually a need to upgrade a pitch. Typically, this will be with a minimum of a sand-gravel slit drainage system being installed, sometimes supplemented with sand banding. Further information is given in section 6.4 of this module.