Lawn aeration

Lawn aeration is one of the most important tasks in lawn care, and if carried out on a regular basis it will vastly improve the quality and health of your lawn.

Why aerate the lawn

The primary goal of lawn aeration is to increase air movement and air flow within the soil and to relieve soil compaction.

All soil types are vulnerable to soil compaction although heavy clay soils are more prone to compaction than light sandy soils due to the smaller soil particles of clay soils.

Compaction is basically a result of compression placed on the soil particles, which in turn causes a breakdown in soil structure. The end result being little or no air available to the soil and a deterioration in lawn health, with weeds, disease, moss, thatch etc. becoming more problematic.

Compaction causes the pore spaces in the soil to become small, thus reducing the amount of air held in the root zone. This inhibits drainage, has a negative effect on rooting, encourages shallow rooted grasses which in turn will reduce drought resistance. Over a period of time lawns can become compact especially if they are heavily used.

The lack of air also has a negative effect on micro organisms in the soil, which need air to survive. Micro organisms play an important role within the soil as they naturally break down the thatch layer and return vital nutrients to the grass plant. Overall a lack of air has a detrimental effect on the health of your lawn.

The benefits of lawn aeration

The purpose of lawn aeration is quite simple, to let air and water into the soil and to relieve soil compaction.

A healthy well aerated lawn has a number of benefits, these benefits include:

• Increase in desirable grasses - When a lawn receives regular aeration it will help to increase more desirable grasses such as bent and fescue grasses.
  
  Bents and fescues are easier to maintain than weed grasses such as annual meadow grass and Yorkshire fog, they are more drought resistant, require less fertiliser and are more disease resistant (especially against fusarium patch).
  
  Quite simply they produce a better quality. (Bents and fescues are the favoured grasses on golf and bowling greens).

• Improved rooting - With regular lawn aeration you will see an improvement in rooting, which produces a healthy drought resistant lawn.

• Increase in micro organisms and beneficial bacteria - Regular lawn aeration encourages a large population of micro organisms. These micro organisms or microbes are beneficial to soil as they promote the natural breakdown of thatch. They are also beneficial in helping with disease resistance as they inhibit the pathogens that causes the disease.

• Helps irrigation during drought - Lawn aeration in the form of shallow slitting or spiking aids irrigation by helping the water go down to the roots and reducing surface run off and water wastage.

• Aids absorption and integration of materials and products into the soil - Products and materials such as top dressing, wetting agents, fertilisers, grass seed are more effective if they are worked into the ground and integrated into the soil.
  
  Therefore, if lawn aeration is carried out prior to these products being applied it will increase the effectiveness of them and can only be of benefit to the health of the lawn.

• Improved drainage - Lawn aeration will improve the drainage by creating channels for the water to penetrate and drain away. This helps keep the lawn surface firmer and drier and will help reduce an potential water logging problems during wetter periods of the year.

• Managing the thatch layer - An excessive layer of thatch is often the main contributory factor in a poor quality lawn. A lawn that contains too much thatch will have poor rooting, poor surface drainage, weed grasses, weeds, moss and very poor grass cover.

  Routine aeration will help control the build up of thatch by increasing the population of micro organisms which degrade thatch.

  Thatch can also be removed by a type of aeration called hollow tining or coring. This involves hollow tubes being punched or inserted into the lawn and plugs of thatch are then removed.

When to aerate your lawn

Lawns should be aerated at least once a year, but ideally they should be aerated twice. The preferred times for lawn aeration are during the spring and autumn as part of the respective lawn care programs. Aerating during these periods means lawn aeration can be incorporated with other operations which compliment each other such as overseeding and top dressing. If you intend to aerate only once a year choose the autumn period if possible.

In most cases lawn aeration is carried out following moss control (if needed) and scarification and prior to overseeding, top dressing and feeding in the spring / autumn programs.

Lawn aeration can however be carried out at any time during the year, subject to ground and soil conditions. Ideally the soil needs to be slightly moist to get the full benefit from aeration, as it is easier for the tines to penetrate and will also prevent any unnecessary damage to the machine or implement being used.

Avoid aerating during frosty conditions, the obvious reason it that you will damage both the grass and the aerator. Also avoid aerating during periods of very wet conditions especially if you are using a heavy machine. Using a garden fork may be acceptable for localised areas prone to flooding, but generally speaking it is best to avoid aerating if the soil is too wet as it can have a detrimental effect.

Generally speaking it is best to avoid aerating the lawn during droughty periods during the summer. However shallow spiking using solid tines may be of benefit to irrigation by creating holes and helping the water to go into the soil where it is most needed. Avoid any deep slit tining during the summer as this can cause the ground to open up and crack if it turns very dry.

The different types of lawn aeration

There are various different types of lawn aeration, with many different implements and machines on the market, ranging from a basic garden fork to sophisticated machinery.

We will explain the different types tines used for lawn aeration and the benefits that each have. They are as follows:

• Spiking or Solid Tining: This is arguably the most common type of aeration on a lawn, due to the fact that most people have a garden fork. However there are also machines available for this task, from push machines to petrol powered aerators.

  The tines of this form of aeration are simply solid metal spikes which are pushed into the soil to create holes. Spiking also called pencil tines can be used at any time of the year, as long as the ground conditions are suitable.

  Spiking is particularly useful during the summer months prior to irrigation to help the water penetrate into the soil profile. Spiking is preferred to slitting in the summer due to fact after slitting, the slits are prone to opening up if it is dry.

• Slitting: Slitting also called chisel tining is not as common as spiking for lawn aeration, however there are benefits of slitting over spiking. They can generally penetrate deeper than spikes and also have the added benefit of root development as slitting prunes the roots.

  Deep slitting would be used in the autumn and winter months. Generally speaking it is best to avoid slitting during the dry season as the spikes are prone to opening up to form large cracks in the surface of the lawn.

• Hollow Tining or Core Aeration: This type of lawn aeration involves the removal of cores from the lawn (see image to the right). The main benefit of hollow tining over other types of lawn aeration would be it removes thatch from the lawn.
  
  It is also very beneficial prior to top dressing as it leaves larger holes (which stay open longer than from other types of aeration). Therefore it is easier to work in top dressing through the holes and into the root zone.
  
  This is ideal if you are trying to change the characteristics of the lawn E.G. You may want to incorporate a peat bases dressing into the soil to improve the water holding properties to improve drought resistance.

  The main drawback to hollowtine aeration or core aeration is that the cores or plugs have to be cleaned up from the lawn surface. Some people prefer leave them and let then degrade naturally, but in most situations is it better if the yare removed. More info on core aeration.

A professional pedestrian aerator, machines similar to this are available for hire for large gardens.		An area of turf after hollow tining. Note how the holes are larger than normal aeration making it ideal to rub in top dressing.

How deep to aerate your lawn

If you are aerating the lawn as part of the spring or autumn program you will want to go the full depth that the machine will allow. In most cases this will be somewhere between 4 - 6 inches (10 - 15cm). Deeper aeration encourages, better and stronger rooting, improved drainage and a better environment for a healthy lawn.

If aeration is too shallow then there is a danger of a compacted layer (Pan) forming just below the surface, hence root growth is restricted, drainage impeded and overall results may be somewhat disappointing.

Therefore in most cases aerate as deep as the implement or machine will allow, but be aware of any drains, pipes, cables etc that may be present under the lawn and adjust the aeration depth accordingly.

The exception to this rule would be spiking during dry conditions during the summer to aid irrigation. In this case just pricking the surface of the lawn would be ideal to help the water penetrate into the root zone.