There can be no life without oxygen! As the picture above illustrates, air is essential if we are to encourage root zone biology and harness the energy and contribution to growth from a beneficial microbial population. Roots do not die due to too much water or compaction; they die due to a lack of air. (Image) – Anaerobic rootzone due to compaction and no aeration operations. New roots only growing at the surface or down old aeration holes.
There are many aeration techniques and equipment available to the turfgrass manager and the choice can be confusing. But what do we mean by AERATION? The word is often used to describe a mechanical operation, e.g. ‘Verti-draining’, ‘Earthquaking’ ‘hollow coring’ or ‘slitting’. Each operation has its benefits but we need to understand what it is we are trying to achieve when choosing the equipment to use, and to match the technique to the situation found.
For a soil to be well aerated there must be an adequate number and a continuity of macro pores through the soil (pores which are larger than 0. 06 mm in diameter are generally considered to be macro pores). Due to the activities of users of turfgrass areas, whether golfers or footballers, the pore spaces in a healthy soil can be squashed, or compacted, especially during soft soil conditions. Activities on very wet soils can result in the destruction of soil structure and is much more severe than compaction.
Compaction can be:
- Surface (upper 75mm of soil)
- Subsurface (lower horizons)
Compaction is likely to occur under the following conditions :
- Lack of earthworm activity
- Poorly structured soils
- Fine textured soils
- Acidic soils
- Excessive traffic, particularly in wet conditions
- Poorly drained soils
- Poor vegetation cover (less than 20%)
- Excessive irrigation
- Inappropriate soils management techniques
RELIEF OF COMPACTION
With this in mind, a turfgrass manager can select the most suitable equipment to introduce air into the root zone. The choice of equipment should meet the following criteria;
- Encourage a uniform and rapid infiltration rate’
- Encourage a uniform and rapid percolation rate
- Establish a continuous matrix of macropores
- Increase oxygen diffusion rates
- Enhance deep, fibrous, explorative rooting
- Create a uniform environment for root growth
- Create a uniform environment for microbes
- Establish uniform moisture availability
- Establish uniform nutrient availability
CHOICE OF EQUIPMENT
There is a vast selection of aeration tools and equipment for the turfgrass manager to consider, from the humble fork (below) to the mighty 100 HP tractor mounted equipment.
During the summer, when the soil is warm and moist, soil microbes are in abundance in the top 150mm and consume vast amounts of air in competition with turfgrass roots. At this time of the year the turf manager also has to contend with golfers who do not appreciate surface disruption caused by heavy equipment. So, we have the highest demand for air by plants and microbes at the time of year when surface have to be at their best.
Equipment that can achieve adequate root zone aeration with little surface disruption is available to the turfgrass manager. A Sarrel Roller, a roller fitted with numerous short spikes, can be used behind a work truck and, if followed by mowing, means it takes no longer than to cut the greens. The shallow and abundant holes allow air to penetrate the turf surface and follow up mowing means that surface levels are restored for the days play. Other suitable equipment includes air injection air through tines, or another that injects water droplets at high pressure.