Gary Beehag looks at some of the new cricket wicket soils that have hit the marketplace in recent times and writes of the importance of knowing their source and physical-chemical qualities before curators decide to use them.
Cricket wicket soils are unique turfgrass growing media. Generally speaking, cricket wicket soil sold in Australia is a mono-soil.
That is to say, each soil type is produced using one source of clay soil as opposed to many construction sands which may be blends of more than one sand source.
Technically called vertisols, because of their high shrinkage/swelling and cracking behaviour, Australian cricket wicket soils are primarily sourced from privately-owned land.
The precise location and production of many cricket wicket soils remains somewhat secretive to their suppliers. Typically, the cricket wicket soil is mechanically excavated from beneath a vegetated surface, screened to size and possibly crushed before storage.
Some sporting facilities in country regions are fortunate in obtaining their cricket wicket soil from within their own property. In NSW and Victoria in recent years, additional and alternative sources of clay soil for cricket wicket construction and topdressing has become available, thus providing more choice in the marketplace.
However, some homework is required by clients given the fact that physical characteristics of wicket soils do not provide all of the answers to the performance of unfamiliar soils.
The earliest published, science-based study of Australian cricket wicket soils dates from the early 1930’s. The specific reasons prompting the selection of Australia’s earliest and two most famous Australian wicket soil types – Bulli soil from Wollongong south of Sydney (NSW) and Merri Creek soil from Beveridge north of Melbourne (Victoria) – is forever lost in time.
From the early 2000s, several sources of commercially-available cricket wicket soils in NSW became unavailable (e.g. Berry, Queanbeyan and Wamberal), while new or alternative sources (e.g. Bungonia and Coolac) have become available.
One additional source of clay soil from the Grampians in Victoria has also recently become available.
Typically, the cricket wicket soil is mechanically excavated from beneath a vegetated surface, screened to size and possibly crushed before storage.
The author is aware of the geographic locations of where the original Bulli soil and Merri Creek soil were first excavated, but sadly are no longer available from their original sites. Nonetheless, black-earth, cracking clay soils from other locations in the Merri Creek Valley have been excavated over the years; some unscrupulously sold in small quantities to unaware clients in Victoria.
In NSW, black-clay soil has been excavated from further sites around Wollongong. Needless to say, the physical-chemical characteristics and consistency of these additional soils vary to lesser or greater extents from the original source.
Current wicket soils
Further, the historical development of cricket wicket soil assessment, albeit based on some false premises and some non-validated laboratory methodologies (e.g. cracking pattern) has been documented.
In recent years, alternative sources of black-earth, high-content clay soils from privately-owned land in southern NSW is being successfully marketed (Table 1).
The colour of cricket wicket clay soil ranges from dark grey to black, depending on source. Soil colour is largely governed by clay and organic matter contents.
Table 1. Typical values of new clay soil sources
|Parameter||Source A||Source B|
|Organic matter (%)||2||1|
Information of the basic chemistry (i.e. pH and salinity), texture (i.e. sand, silt and clay) and organic matter content allows clients to make an informed decision when purchasing unfamiliar cricket wicket soil. Similarities, as well as differences, based on accredited-laboratory test results of a current and unfamiliar source of cricket wicket soil can be compared.
However, acceptable performance of a wicket soil for a traditional Test match cannot be predictably assessed from measuring soil texture and organic content alone.
On relatively new cricket tables the source, supplier and basic physical-chemical properties of the wicket soil is probably known. In stark contrast, the source, depth and basic properties of clay soils beneath many older cricket tables, particularly in country regional areas, may be unclear even unknown.
For many of these older turfgrass cricket wicket tables, the soil currently used for topdressing or re-levelling purposes is unlikely to be from the same source, as was the original construction soil. Do you know of the nature and source and have a laboratory analysis of the original construction soil beneath your wicket?
A common question asked among cricket curators and others concerns the textural thus physical compatibility of different sources of wicket soils (see photo below).
This question arises for topdressing purposes or when re-levelling. Does this question infer that different sources of high-clay content soils are by their nature physically incompatible causing delamination at their interface and, if so, how can the degree of compatibility or alternatively incompatibility be objectively measured?
Physical engineering measurements of plasticity (range of water content over which clay soils remain in a plastic state) and coherence (ability to hold together when dry) of clay soils is widely practiced in civil engineering.
In Great Britain, where the clay content of their wicket soils is around 30 per cent, the “motty” or Adams/Stewart Soil Binding test adopted to measure soil strength has been modified in an attempt to quantify compatibility between different clay soil types.
Differences in shrinkage/swelling and cracking behaviour between different clay soils has been partly attributed to their clay content and mineralogy.
Examples of different wicket clay soil shrinkages and cracking
Here in Australia, any investigations conducted into physical compatibility between different cricket wicket clay soils has not been published. The author has observed various degrees of shrinkage and cracking of unreplicated cricket soil mixtures following their blending in small quantities when dry and crushed then remoulded in a moist state.
Some previous commercially-available cricket wicket soils have been the result of uncontrolled blends between two different clay soil types. Nonetheless, many cricket wicket curators have produced acceptable wickets when using a clay soil different from the original construction type for their topdressing and surface rejuvenation purposes, the key being to remove from the surface all partly-decomposed organic matter accumulation and loose soil.
Wicket soil recycling
As previously mentioned, the physical-chemical properties, source and consistency of wicket clay soil beneath very old wicket tables, particularly in regional areas, is often unknown.
However, while the recoverable volume of existing wicket soil beneath old wickets may be significant on large-sized tables, its physical quality and consistency always remains questionable.
Inevitably, the organic content increases because of only partial decomposition of plant issues over time in old wickets.
In some cases where the nature and origin of the wicket soil is known and its field performance is acceptable, any excavated soil could be salvaged by the cricket facility for potential re-use at the same site. Of course, any future use will require the salvaged soil to undergo processing and storage.
Excavation and salvage of wicket soil from old wicket tables presents marketing and legislative issues for cricket wicket soil suppliers. Nevertheless, there are numerous examples of excavated wicket soil having been excavated and stockpiled in all sorts of locations by clients in urban and suburban regions. While feasible, the economic benefits of salvaging and re-processing excavated soil require assessment.
Wicket soil suppliers are unlikely to want the excavated product for re-sale in view of its unknown nature, let alone questions about soil purity, quality and consistency. Further, what of future couchgrass contamination from the re-growth of live rhizomes in the salvaged soil?
Marketing of recovered wicket soil of unproven nature and source against a proven ‘virgin’ soil may prove problematic. Furthermore, there becomes the issue of how to physically change and stockpile the excavated material into a usable product then store under all weather conditions for future use.
A take home message. When purchasing unfamiliar cricket wicket soil, be aware of its source and physical-chemical qualities. Request a copy of the most recent laboratory test report. When topdressing or rejuvenating an existing wicket, know the nature and properties of the underlying clay soil. If unknown, have a physical and basic chemical test conducted on at least one sample. Let the buyer and user beware.
This article originally appeared in volume 21.4 of the Australian Turfgrass Management Journal. To subscribe to the magazine click here. Members receive the publication included in their membership.