Routine Aeration

ROUTINE AERATION

Routine aeration is the aeration the Groundstaff can do every year to help to maintain pitch performance. Traditionally this maintenance is performed as part of end of season pitch renovations.

This section of the guidelines look at two types of aeration that can really help pitch performance – deep scarification and solid tine aeration. These two methods can help achieve better pace and bounce, improved consistency and better grass growth.

Post-season Deep Scarification

Thatch is the enemy of good pace and bounce. It makes the pitch less hard at the surface, reducing pace and either lowering bounce or making it more like a tennis ball. To find out more about how thatch affects ball behaviour, look at: ProfileBallBounce.docx

Thatch is the fibrous layer of slowly decaying grass stems, roots and crowns that forms at the top of the profile over time. Because the grass is cut so short on cricket pitches the supply of thatch material is high. In natural soils, thatch is broken down and used as food by soil organisms but in intensively managed, dense cricket pitches this natural cycling does not happen, because of low oxygen content in the soil, chemical use and the inhibition of earthworm activity. This combination of high rates of material input but low rates of breakdown mean that thatch formation rates in cricket pitches can be high.

This means that rather than microbes breaking the thatch down, it needs to be mechanically removed and deep aeration is an excellent method for doing this. Deep scarifiers have powered blades on a reel that are strong enough to penetrate into the cricket pitch and lift grass and thatch to the surface. They can work effectively to 30-40 mm, aim to get at least 20 mm of penetration into the surface. You can measure this by using a thin knife blade or similar. The deep scarifier can be used in three directions across the square to help lift thatch.

Figure 1 Blades on a tractor mounted deep scarifier

The removed thatch and grass materials should be collected by the machine or swept up and taken away for composting. It should not be allowed to rest on the surface to be re-compacted into the surface at a later stage. The first time you use a deep scarifier you might be alarmed by the volume of material removed but persist and your pitches will benefit.

Figure 2 Deep scarification (with arisings removed). Note how only a limited amount of thatch is removed with each pass - this is because to remove all thatch would require complete cultivation of the surface which is not desirable in an annual maintenance regime.

This process is usually followed by topdressing to restore levels and overseeding. In profiles with an identified thatch problem, deep scarification should always precede topdressing otherwise thatch layers can be buried deeper into the profile, making them more difficult to remove.

Incorporating this into your annual post-season maintenance programme will help prevent the accumulation of thatch and the burying of thatch in the profile by annual topdressing. This should be seen as an essential – every year job, even on a new square. It is all about prevention being better than cure. Sometimes, thatch content will be too high or the thatch itself will be too deep in the profile to be controlled by deep scarification and different removal methods will be required. If you suspect this is the case – then take a look at how you can use other techniques to solve deep or heavy thatch by clicking here and following our problem led approach.

Solid Tine Aeration

Solid tine aerators are designed to mimic a fork being pushed into the soil. Solid tines are punched into the soil to make holes of the same diameter as the tine and to a specific depth, controlled partly by the machine but also soil conditions. On a cricket square the tines should always be set to enter the soil vertically and exit vertically so that the profile is not lifted. On a rugby pitch, the tines can be set to exit the soil diagonally, lifting the soil upwards slightly to loosen it but on fine turf surfaces heave should be limited to maintain surface levels. Figure 3 shows a solid tine aerator in use on a cricket square. Note that this section does not refer to the use of spiked drum rollers (Sarrel Rollers) which have a benefit in helping to produce seed beds in renovated pitches but were shown in our trials to cause significant compaction and no aeration benefit when used in October-November to try and aerate cricket pitches.

Figure 3 Close up of a tractor-mounted solid tine aerator in operation. Each head holds four tines and the heads are set on a cam which drives them into the ground (at high speed). The tines used here are narrow (7 mm) so that they penetrate into the hard square. Larger diameter tines can be used on outfields which are not usually as hard as the square. The depth of operation is set by the rear roller which lifts the equipment up and down relative to the ground.

Solid tine aerators are commonly used on cricket pitches with varying degrees of success. The following guidelines will help you maximise the benefit of solid tine aeration but first of all it’s important to understand why you would use a solid tine aerator and what it actually does and doesn’t do.

Why use a solid tine aerator?

When set to work vertically, as on a cricket square, solid tine aerators do not ‘decompact’ the profile – they do not reduce the density and do not make it less hard (this has been shown in a number of experiments in the research at Cranfield University). So why use them on a square?

Well, although they don’t decompact the soil, the tine holes make channels down which plant roots can grow (these channels can persist for a number of years, long after the tine holes are closed up at the surface). The channels also allow oxygen to move into the profile at depth – not in large quantities but it can help. It can also help get water into the profile by increasing infiltration rate – although this doesn’t always happen (see below).

So think of solid tine aeration on the square as making channels for grass roots and making pathways for air to get into the soil (until they are sealed at the surface). Don’t think of it as loosening the soil all the way through the profile – don’t worry about decompaction – the natural shrink and swell of the soil will be far more effective.

Solid Tine Aerators

The solid tine aerator comprises a series of solid tines that are driven into the ground using a cam-action. The tines are mounted on a cam that is powered either by a petrol engine on a pedestrian machine or by the PTO on a tractor mounted machine. Generally, pedestrian machines allow greater flexibility of use as they are lighter but tractor mounted machines are wider, more powerful and heavier and as a result achieve greater working depths and work rates.

The key thing with solid tine aerators is using them at the right time and in the right way. The ‘right time’ depends on soil conditions and the window for optimum use is not open for long. Right at the end of the season the pitches are often too dry and hard (particularly if they have been covered) to get the tines into a good depth (> 75 mm). If tines are used when the pitch is too dry they can lift and pull the square upwards which can cause real problems and damage the square. Rain and water help soften the pitch to allow the tines to go in further and as a result squares usually receive solid tine aeration in late October / November. However if the soil is too wet it just moulds around the tine and makes a sealed hole in the ground which just fills with water. This might break up in time but can really limit the benefit of solid tine aeration.

Our research showed that the effects and benefits of solid tine aeration are variable from year to year and this is dependent upon soil conditions at the time of aeration. The best time to use a solid tine aerator is when the soil is just wet enough to get the tine in to a good working depth without damaging the surface by pulling it upwards. Using narrower tines can help because there is less soil resistance but it is important that they do not snap in the pitch because they can be very difficult to remove!

Timing of the operation of course depends on having a machine to hand. Unfortunately spiking equipment can be expensive and if it’s only used to aerate 600 m2 (an 8-pitch square) once or twice a year, the cost of buying one needs to be considered carefully. Renting an aerator or borrowing one from your county trailer might be a more cost effective option, but it also makes it a little more difficult to do the spiking at the right time.

Look to use a solid tine aerator as soon as you can post season without damaging the pitch. If this can be done prior to topdressing and seeding it can help with germination and in maintaining surface levels.

It is really important to evaluate the effectiveness of scarification and aeration. Use core samplers to look at thatch content and rooting depth in your profile. This will help you tailor your maintenance to your square. For advice on taking and interpreting cores, click here.

And to find out more about solid tine aerators – see: 06 Stage 4.docx

Problem Solving with Aeration

Disclaimer : These guidelines are based on research data and experience from a project conducted at Cranfield University. Neither Cranfield University or TGMS Ltd accept any liability for the results of that project or for the use or uses to which these are put or for the effects, consequences or otherwise of maintenance of any facilities, or the actions of any contractors employed, as a result of, or in connection with, any information provided in these guidelines. Cranfield University and TGMS Ltd are independent organisations. No recommendation of any product or service supplier is made in this report whether implied or otherwise. All costings in these guidelines are indicative and are not a current survey of market prices. All costs were current as per the date of these guidelines.