The Science of Aeration

Regular and seasonal aeration is essential to ensure turfgrass quality is maintained throughout the playing seasons at most fine turf and field turf facilities. The impact and cost of not carrying out these operations can be high, resulting in lost or canceled fixtures, which will have other impacts for club members and users, often resulting in lost revenue for the facility.

What is the purpose of aeration?

The vast majority of turfgrass swards are grown in a medium consisting of a blend of soil and sand (in varying degrees) that provide a suitable environment for plant growth. This growing medium, commonly referred to as the root zone, is made up of differing proportions of soil solids (mineral and organic material) and soil pores (spaces for water and air).

Maintaining the correct balance of these components is critical for sustaining healthy plant growth. The spaces between the particles of solid material are just as important to the nature of soil, as are the solids themselves. It is in these pore spaces that the environment is created for the plant to obtain the necessary nutrients, air and water, it requires to respiration and growth.

These pore spaces can vary in size and are generally classified into two sizes - macropores (larger than 0.08mm) and micropores (less than 0.08mm). Macropores generally allow the movement of air and the drainage of water, and are large enough to accommodate plant roots and the micro-organisms found in the soil. The ability to retain a good balance of macropores in soil structure is essential for maintaining grass plant health. It is when these macropores are either reduced in size, or filled with water, that we see deterioration in surface playability and resistance to wear.

The main contributing factor that reduces and damages pore spaces in soil is compaction, typically caused by compression forces normally associated with play and use of machinery, particularly during wet weather periods. Over time, these compression forces reduce the pore spaces so that air, water and nutrient flow through the soil profile is restricted, and leads to the many problems associated with compaction.

There are two distinct types of problems on winter games surfaces; one is compaction by treading (30-60mm depth) and the other by smearing and kneading (30mm depth). Compaction has been measured down to depths of 120-150mm on horse racing tracks.

The extent of compaction is also dependent on the soil type. Clay, clay loam, silt and sandy soils will all compact, but the majority of compaction problems are associated with the heavier soils - clay and clay loams. 

Compaction can result in having a saturated soil, which reduces the soil strength and often results in loss of groundcover. Once grass cover is lost, the surface is more susceptible to weed invasion and common weeds on community winter sports pitches are a good early indicator of compaction issues.

Compacted or sealed surfaces can also promote anaerobic soil conditions (i.e. the soil has little or no oxygen) and this will reduce root growth and restrict microbial activity.

These conditions will adversely affect a surface’s performance in many ways, such as ball bounce, ball roll, reduced ball speed, player welfare and, in the long term, damage the soil structure, which may lead to expensive reconstruction costs.

How Do We Aerate?

To alleviate these compacted layers, we need to consider a range of different techniques and equipment that can encompass the different types of playing surfaces (fine turf and field turf facilities). The main aim of aeration is to penetrate the soil profile to create new macropore space.

This is achieved by several methods:

• Solid tines - hand forks, pedestrian and tractor mounted vertical punch aerators
• Hollow/coring tines that remove soil cores from the soil
• Flat/star tines
• Disc/blade implements (linear aerators). A number of machines on the market are designed to open up the ground and back fill with permeable materials
• Compressed air and water injection aerator systems
• Drill and fill machines

It is essential to use a variety of aeration techniques to prevent pan layers being created. This usually happens if you continue to use the same aeration technique set at the same depth, resulting in a compacted layer forming at the base of the tine or core depth. Most turfgrass managers will, therefore, vary the methods of aeration by changing the depths, size and diameter of tines.

The variety and choice of implements and devices now available is excellent, providing different tine sizes, operating widths and soil shattering features that can meet the requirements of any facility and, more importantly, do not disturb the playing surface, allowing play to continue after use.

The benefits of aeration

• Improves soil surface drainage (water infiltration)
• Helps to increase soil temperatures
• Increases soil pore space - allows gaseous exchanges in the soil (oxygen in, carbon dioxide out) that improves root growth and development
• Aids integration of topdressings into the soil profile
• Aids the breakdown of thatch/organic matter
• Promotes better surface levels that will increase ball roll /speed
• Aids surface firmness/dryness, thereby increasing ball bounce and surface grip

It goes without saying that aeration plays an important role in the management of natural turf playing surfaces and should be a key operation to aid turf grass performance. However, be mindful what technique or machine you choose to use on your playing surface. Using a variety of aeration techniques and machines, modern day grass surfaces can remain playable all-year round.