STAGE 5: THE AERATION TREATMENT – METHOD AND TIMING
Having matched the aeration equipment to the problem identified, for the equipment to be effective it must be operated using the correct method at the correct time.
This page does not aim to provide specific advice on individual machines but focuses on patterns of work and timing of operations. It is essential that machinery is only operated by trained, competent and experienced personnel and in accordance with manufacturer operation manuals. A health and safety risk assessment should be completed for the operation of all equipment. The Institute of Groundsmanship provide training on the operation of equipment and conducting relevant Health and Safety Risk Assessments (see www.iog.org for more details).
Timing operations based on soil conditions
The majority of aeration treatments occur post season – this is because it minimises the impact on pitch preparation and performance and because soil conditions are generally wetter. Historically operations such as solid tine aeration have taken place when soils are wetter to allow better tine penetration and reduce wear on parts (and operators!). Operating in wet conditions reduces the risk of surface damage (up to the point where the machine damages the surface as it passes over it) but does reduce the effectiveness of the operation however. This is because effectiveness is related to soil consistency. To learn more about soil consistency click here.
Machinery set up and measuring working depth
With all machinery – set up is critical and you should consult the manufacturer’s operating manual to ensure that set up is correct. Always do trial runs before operating machinery on critical areas – for example start at the edges of the square to ensure that set up is correct.
Always measure working depth in the field – do not just rely on machinery depth gauges, these are for easily deformed soils and don’t apply to cricket pitches. To measure working depth in the field use a thin blade, screwdriver or bike wheel spoke and push it into the hole/slot the machine has created pull it out and measure the working depth against a measuring tape or ruler.
Adjust the machine’s working depth controls until the desired working depth is achieved in the actual soil conditions you are working in. Note that it might not be possible to achieve your desired working depth (i.e. beyond the depth of the problem you identified in Stage 3) with the equipment you are using due to soil resistance – if this is the case consider reducing tine diameter (in the case of solid tine aerators) or increasing the size of the machine you are using by hiring in tractor-mounted equipment (but do not increase the size of the tines). An alternative is to wait until soils become wetter and lose their strength – however this might result in conditions where the soil will be damaged by the machine at the surface or any penetrating tine etc only smears the soil and does not fracture it effectively.
Using scarifiers and rakes in-season to minimise thatch accumulation
Scarifiers, verti-cutters or hand rakes should be used as part of pitch preparation prior to mowing to help encourage vertical grass growth and limit the accumulation of thatch. Powered scarifiers should be used in the direction of play to avoid affecting the presentation of adjacent pitches. Hand scarifiers can be used across the direction of play but will have a slower work rate than when used in the direction of play. As well as limiting thatch accumulation, this process will also thin the grass sward improving pitch performance. Note that it will not prevent thatch accumulation entirely and other measures will be required to help reduce thatch content.
The scarifier should also be used following pitch use, prior to in-season renovation to help limit thatch accumulation and to lift grass trampled by players.
Post season Deep Scarification
If you have identified a thatch problem that is near surface then a deep scarification will help. Deep scarification is usually conducted post season as the initial stage of square renovations. The deep scarifier can be used in three directions across the square to help lift thatch. Lifted thatch should be removed and composted sustainably. It should not be allowed to rest on the surface to be recompacted 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.
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.
Fraise Mowing and Surface Planing
Fraise mowing and surface planing should be conducted at the end of the season in dry soil conditions. It is strongly recommended that clubs engage reputable, experienced and suitably qualified cricket maintenance/construction contractors to carry out this work. As these methods commonly involve the handling of larger quantities of cricket loam it is essential that the work is carried out in dry conditions. Cricket loam should not be handled when wet as it will not apply uniformly as a top dressing and will not structure properly when used in reconstruction.
Solid Tine Aeration – Pitches and Squares
The majority of solid tine aeration takes place post season, once soils have become wetter and tine penetration is possible. This is usually mid-October to early-November. Note that soils might be too wet for effective aeration by this stage (depending on rainfall). The solid tine aerator should not be used when conditions are so dry that damage to the profile, the equipment or the operator occurs. Using a solid tine aerator when the soil is too wet reduces effectiveness however. There is a ‘sweet spot’ in between these conditions where solid tine aeration is most effective. It can be identified as the soil water content at which tines just penetrate to working depth without damaging the surface and can be found by trial and error (on the outside wickets of the square) but tend towards the wetter – slightly less effective aeration is much less of a problem than shallow tine penetration (less than 50 mm) which will lift the surface of the pitch as the tine is pulled out.
For a number of years, Keith Exton, the Head Groundsman at Glamorgan County Cricket Club has successfully used a tractor mounted solid tine aerator in-season. He does this by matching tine diameter to soil conditions. As discussed in Stage 4, reducing tine diameter reduces soil resistance and allows the equipment to be used in drier conditions. Reducing tine diameter can help but will require the purchase of new tines and can result in tines snapping or bending when ground conditions are too hard. It is essential, whatever the diameter to ensure that the tines are penetrating more than 50 mm to ensure that the surface is not lifted as the tines are pulled out.
Figure 1 Solid tines mounted on a cam in a tractor mounted solid tine aerator.
Solid tine aeration can be conducted across the square to help limit the number of turns and increase work rate but should be done in the direction of play if different pitches are at different stages of construction (e.g. new pitches being allowed to structure before being used). The aeration trials at Cranfield University showed that there was not necessarily a benefit from conducting this operation every year, with the largest effects observed in Year 1 and diminishing returns in Years 2 and 3. It could be that solid tine aeration is beneficial on a 3-4 year cycle but this will depend on soil profile quality. The Cranfield University results are on profiles that are not layered. In profiles that are layered – annual solid tine aeration could be justified but this needs to be monitored using profile cores (see Stages 6). The Cranfield University trials also showed that there was no benefit from repeat applications in the same year because soils became too wet later into the winter. A single operation in the right soil conditions is more effective.
Another tip is to vary the depth each time you aerate between a minimum of to the max depth available with the machine/tine combination. Using the same single tine depth continuously year after year can result in a compaction ‘pan’ being formed.
Solid Tine Aeration – Outfields
The very wet weather in 2012 has highlighted the poor condition of many outfields which are compacted and have very low infiltration rates. This has occurred because the focus has been on mowing and smoothing outfields but not on infiltration of water. This has resulted in many outfields being flooded and flooded for longer. Obviously there is a limit to how much infiltration can take place but decompacting outfields will help with infiltration rate.
Because of the large size of outfields this can be an expensive operation but it is effective. The job requires large tractor-mounted solid tine aerators to achieve effective work rates. A small amount of heave will help decompact the outfield – but not excessive heave which will affect ball roll.
Timing is important – soil conditions should be friable (see explanation) and this will depend on the weather and type of soil. Timing also depends on whether outfields are used for winter sports – it is often beneficial to relieve surface compaction from winter sports before the cricket season or at the end of the season to help hard outfields be used for Rugby Union pitches.
Just as with their squares, clubs should take core samples and investigate their outfield soil profiles – and treat the problems accordingly. Even targeted solid tining in persistently wet areas or heavily trafficked areas will help.
Figure 2 Solid tine aeration on the outfield at the Kia Oval cricket ground
Drilling operations should be post season in dry conditions as the equipment is relatively heavy. Deep Drilling can take place as part of the post season renovation following scarification, top dressing and overseeding. This prevents the drill holes being filled with topdressing but care must be taken when clearing the soil excavated by the drill. For that reason, overseeding can take place following drilling, where necessary.
Figure 3 Deep drill aerator (side view). Note the spoil left by the machine (right) which needs to be cleared prior to topdressing.
Drill and Fill
Drill and Fill operations will disturb the soil profile and should therefore be done as the first operation post season, after dethatching/deep scarification. Topdressing and overseeding should then follow to ensure levels are correct.
On average it takes 4-5 days to complete the drill and fill of four pitches on a double pass of the machine using 25mm drill bits (in good weather).Drilling takes place on Day 1, along with clearance of the spoil at each pass. The remaining three to four days are spent filling the holes by hand (usually a team of three) and final clean up at the finish.
Surface reconstruction should take place at the end of the season so that it does not disrupt play during the season and to allow maximum time for soils to restructure and grass wards to establish. Clubs are advised to get advice from their County Pitch Advisor or a suitably experienced and qualified consultant when undertaking pitch reconstruction works. The work is best carried out by experienced cricket construction contractors. Speak to your County Pitch Advisor for more information.