Football Pitch Maintenance: 13. Aeration

Aeration work is essential if good root growth is to be encouraged. This can be achieved through routine slit tining (especially on sandier rootzones with minimal stones within it), heavier chisel-slit tines where the soil is more compacted and prone to having stones and other inclusions within a rootzone and solid tining.

To reduce soil density then the removal of soil cores by the use of hollow-tines is essential, although decompaction can disturb and shattered the soil profile, reducing soil bulk density, thereby creating numerous fissures for drainage and root growth to take place.

Timing of any aeration work is key as carrying out the work when it is too moist or wet aeration tines will smear the soil surface and sides of a soil profile. If the soil is too dry, then tine penetration is either negligible or will just bounce along the surface of a pitch because the ground is too hard.

The injection of compressed air into the soil profile is another means of aeration and can be especially effective on soils that are on the slightly moist to dry side, thereby allowing for fissuring to occur within the soil profile due to the outward movement of the compressed air. Where the soil is very compacted, the use of solid tines to penetrate the surface layer may be beneficial to reduce the likelihood of compressed air being redirected back up from a compacted soil layer and out through the turf layer. Where the turf has been solid tine aerated beforehand the holes can act as a sort of pressure relief valve and this can reduce the amount of turf heave or turf lift that might occur where the compressed air is proving too high for the soil profile to adequately take in.

For many soil-based pitches, which are the majority in the UK by far, in contrast to specially constructed sand-based, the ‘window of opportunity’ for effective aeration and decompaction can be short and limited due to the rainfall patterns encountered in the country. September can often be an optimum time for the most effective deep decompaction and aeration work to take place, as it is still dry from after the summer months, but not too hard as would occur in early summer, nor would it be too wet – as would occur over most of the winter months.

Slit tine aeration under unsuitably moist-wet soil conditions can result in a slightly increased loss of ground cover when compared to a pitch not having any slit tine aeration work carried out. These conditions can be considered, in general terms, as being where the upper limit for natural drainage has not been reached and water is still within the soil profile and it still needs to drain away naturally, i.e. field capacity has not yet been reached) and when grass growth is minimal, which is over the majority of the mid-late parts of the playing season from around November to March, (Baker, S.W. (1994), ‘The effect and frequency of slit tine aeration on the quality of soccer and rugby pitches’, The Journal of the Sports Turf Research Institute, Vol.70, June 1994, pp44-54).

To reduce smearing of soil from slit tine usage and smearing on the surface, as well as causing unacceptable compaction, from the type of equipment and machinery being used, then the soil moisture content would typically be below field capacity when this activity takes place. The exact level of soil moisture content may ideally be below field capacity by say x% and this would vary according to soil type: In practice this is where the skill and knowledge of the locally based experienced grounds operative is invaluable as they will have the local knowledge to help best determine optimum times for the carrying out of slit tine aeration.

Varying the depth of routine aeration work will help to reduce the potential of an aeration pan developing. Shallow slit tine aeration using a combination implement along with some interspersed deeper tine aeration to maybe 150-225mm would be useful approach. This would then be supported by heavier duty decompaction work when soil conditions are suitable for ensuring adequate shattering of the soil profile can take place.