Daniel Ratling BSc Hons., Head Groundsman at Whitgift School, has recently completed a year-long research project studying cricket loam compatibility. In this article, he outlines the issues around incompatibility, how the constituent parts affect the process and how this might be applied practically
I have worked in and around cricket pitches all of my professional life, and one thing that increasingly interests me is the way that the different constituent parts of a cricket loam interact to produce the hard, tightly bound pitches we strive for.
As cricket groundsmen, we are acutely aware of the importance of a homogeneous cricket square soil profile and the benefits this confers for playing characteristics and ease of management. This came to the fore recently when I was told that my loam distributor was closing and could not supply the materials required for our end of season renovations at Whitgift School, where I am Head Groundsman. The irony was not lost on me that this news came just six days after completing a year long research project studying cricket loam compatibility for the final year dissertation for my BSc (Hons.) with Myerscough College.
The decision to change the loam used on a cricket square should not be taken lightly due to the potential performance issues associated with layering incompatible materials. However, sometimes, one's hand is forced, whether it be for pitch performance issues or a defunct loam manufacturer.
The interactions between the constituent parts of cricket loams are interesting and sometimes complex. Somewhat surprisingly, little research exists directly related to cricket loam compatibility.
This article outlines issues around incompatibility and discusses how the loam constituents affect that process, as well as how this might be applied practically when selecting a compatible material.
Incompatibility and Testing:
For a loam soil to be used as a cricket loam, it must be strong enough not to deform on impact with a cricket ball. The ECB recommend clay contents of 25-35% and breaking strengths of 55-90kg, although we know, from analysis, that some commercial loams have slightly lower clay contents than this and provide adequate surfaces for lower level cricket. Consideration must be given to pitch performance characteristics and also to the resources a club has to manage their pitch preparation. Higher clay contents mean greater strength, but more management, especially in terms of drying rates and vertical cracking stability.
Making the assumption that the loams tested for compatibility are of sufficient strength to be used for cricket, it is the matching of shrinkage rates that is of paramount importance for compatibility. Incompatible materials can lead to problems, resulting in low or variable bounce. This is as a result of distinct layers becoming evident within the soil profile.
Root breaks, which are horizontal fissures at the interface between materials, impede root development and deaden ball bounce. This is due primarily to different shrinkage characteristics of the layered materials.
To ascertain the suitability of a product for use as a cricket loam, tests for strength and shrinkage should be carried out. Most reputable manufacturers will supply you with data sheets for their cricket loams with this information. However, if testing for compatibility, it is worth taking time to run a series of tests using the modified ASSB (Adams and Stewart Soil Binding) method combining halves of the native loam used on the square and the potential replacement loam.
If two materials have vastly different shrinkage rates, it is possible they will separate as the prepared composite motty dries. Assuming that the composite motties remain intact following drying, testing for strength using the ASSB method should be carried out. Compatible loams will hold together at a greater applied pressure, i.e. they are stronger. Where loams may be incompatible, they will separate at the interface between the combined materials, often at a lower applied pressure. I found it useful to run some standard ASSB tests on motties made from a single loam to give strength data for comparison with the composite motties.
Cricket Loam Constituents:
Clay content is rightly the first constituent part to be considered when selecting a cricket loam for compatibility. Clay content of a cricket loam typically accounts for around 25-35% of the loam material, yet it confers many of the most important characteristics required for cricket pitch performance.
Once wetted, it is the plasticity of the clay that allows it to be worked with a smooth roller into a surface suitable for cricket. Upon drying, clay gives the loam its strength, which is a requirement for good consistent pace and bounce. In my research project, clay content by far had the most significant effect on strength of the composite motties.
If selecting a replacement loam for performance issues associated with improved pace and bounce, and working on the assumption that you have a homogeneous square profile to which to add a new loam, it would seem sensible to look for an increase in clay content. However, it is short sighted to select compatible loams on clay content alone.
We know that all of the loam constituents have some bearing on strength of a cricket loam. It is the broad range of particle sizes in cricket loams that allow for increasing degrees of particle inter-packing and higher bulk density; think the opposite of a uniformly distributed USGA golf putting green rootzone. When considering that the silt and sand fraction may account for as much as three quarters of the loam material, it seems obvious that they must have some influence on a cricket loams performance.
Interestingly, silt has been shown to be negatively correlated with strength when considered alongside clay whilst, conversely, sand has been positively correlated with strength. In either case, it would seem that it is the interaction with the clay fraction, overall clay content and the overall range of particle size (including silt and sand) that is critical in determining strength.
When considering shrinkage of a cricket loam clay content and, to a lesser extent, clay mineralogy should be considered. Two materials with vastly different clay contents will likely shrink at different rates. Mineralogy is less of an issue with many of the commercially available loams, having a similar mineral make-up of the clay fraction. Of the loams I tested, there was only one notable exception with an obviously differing mineralogy; however, mineralogy was not shown to have a significant effect on either strength or shrinkage.
Silt content and sand content have been shown to effect cricket loam shrinkage rates. It is possible that an increased amount of smaller silt and clay particles allows for a greater degree of particle inter-packing on contraction of the soil when drying although, without external compaction forces, it is not clear how this particle reorganisation would take place. It is perhaps more likely that water held in mesopores (medium-sized pores) and around the silt particles evaporates as the motty dries, causing greater shrinkage.
Of the five loams tested, all had organic matter contents between 2-8%, which is the ECB recommended guideline for organic matter in topdressings. Organic matter is known to absorb water, deaden ball bounce and reduce soil binding strength but, in the quantities seen in the research, it was not thought as much of an issue as surface accumulations. This brings to the fore the need to clean a surface thoroughly before applying a topdressing, possibly even more important if introducing a new loam to the square.
Ideally, one would continue to topdress a cricket square with the loam with which it was constructed. In the eventuality that a change of loams is required, it is prudent to carry out some simple tests to ascertain the suitability of a compatible material.
One thing for sure is that all of the loam constituents must be considered when selecting a loam for compatibility. Unless changing loam for performance issues, it would seem sensible to match as closely as possible all of the constituent parts or, put another way, match the particle size distribution.
Things change a bit if looking for higher clay content loams but, again, some consideration should also be given to the silt and sand contents and how the constituents interact and the rate at which shrinkage occurs. As stated before, differing shrinkage rates between layered materials can lead to horizontal fissures at the interface between those materials which, upon drying, can cause variable and slow and/or low bounce. Such an outcome would be counterproductive if the aim is to improve pitch performance.
The interactions between the various constituent parts of cricket loams are potentially complex and this article only offers a brief overview of the subject. It does, however, make the point that if you were in any doubt at all; all constituent parts of a cricket loam exert some effect on its behaviour and must be considered as part of the selection process for a compatible material.
- Only topdress with compatible cricket loams
- Carry out a modified ASSB test to ascertain compatibility between loams
- Strength is important, but matching shrinkage rates is absolutely key to compatibility
- All constituents of a cricket loam must be considered when selecting cricket loams for compatibility
Daniel's research project was the culmination of five years of online study. The BSc (Hons.) Sports Turf Science and Management was studied online with Myerscough College over two years, following the completion of the FdSc Sports Turf Science, which was studied online over three years.
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