Pre-season rolling is, for many cricket
groundsmen, one of the most important and
challenging processes used in the preparation of hard, fast, and
bouncy cricket wickets. However, there are no set rules or guidelines for the process and, if not understood, it can have severe
consequences. This
article is an attempt to describe some of the main points about pre-season rolling and some of the theory
behind it. To begin with, I’ll be a looking at the
frequency and intensity of rolling then the
weight/footprint of pre-season rolling.
Only soils that
somewhere in between, the middle point being field capacity. Soil strength is similar, as it also has two extremes - elastic (hard) and plastic (soft). The middle point of soil strength is also at field capacity and, at this point, there are an equal number of pore spaces filled with water as there are filled with air (air- filled porosity).
The significance of field capacity on
soil strength is that the greatest amount of consolidation can only take place when there's sufficient lubricant (water) and soil pores (air spaces) within the soil. As the moisture level moves from field capacity to wilting point, so the efficiency of consolidation is gradually diminished. To compensate for this, a heavier roller can be employed to increase efficiency and, therefore, its effects. The diameter-to-weight ratio of rollers also plays a major part in the consolidation process. Basically, the greater the diameter and the lighter the roller the less chance of creating a steep bow wave. It is worth mentioning that a bow wave is always created when rolling but, in the majority of cases, not steep enough to cause any damage to the wicket profile. Steep bow waves are caused by using too heavy a roller with too small a diameter (a pedestrian trailed mower seat maybe!), and do cause damage which generally includes:
1. Root shear 2. Surface rucking
Root shear:
in conjunction with Bob Scott (British Seed Houses)
By Colin Ashman
water moves through the soil (the hydraulic conductivity) is slower on heavy clay soils such as those used for cricket wickets. Therefore, during periods of rainfall, the moisture content of the wicket deeper down is less affected as most of the rain will become surface run off.
Weight/footprint:
Soil moisture levels can be classed as either extremely wet, extremely dry or
This is caused when the bow wave is steep enough to precede the roller from one end of the wicket to the other, causing the delicate roots to shear at a consistent point below the surface of the wicket, usually within the 4” (100mm) of wicket soil needed for good bounce and pace. By shearing the roots, what will dry the wicket now? Root shear will cause the wickets to become very hard on top but behave slow and low. This is because the wicket is still wet underneath thereby absorbing the ball’s energy. Evaporation rates (the sun drying the soil directly) in the UK can generally only dry a soil out to a depth of 1" (25mm). It is the loss of water due to the processes of transpiration through the roots of grasses, as well as the effects of evaporation (evapotransporation), that dry wickets to depth, creating harder and faster wickets.
have dried sufficiently should be considered for heavier rolling
Surface rucking:
A bow wave is created and then becomes so steep that it is driven over by the roller, which then goes on to create another bow wave until it, too, is too big for the roller to push and is then also ridden over. This causes the surface of the wicket to become very uneven, and there is little chance of an immediate remedy: usually years of judicious topdressing or using a machine such as the Koro Fieldtopmaker. It is advocated that wickets should be
rolled in many different directions during pre-season to cause equal consolidation, and also to reduce the effects of surface rucking, if any. It is also advised not to roll stump to stump too early for the same reason.
Summary:
At field capacity the efficiency of consolidation is at its maximum. Wicket soils will remain at or near field capacity during the pre-season until grass growth increases the rate of transpiration, therefore drying the wicket, at which point pre-season rolling should commence. As the turfgrass growth rate increases so does the rate of wicket drying, and the efficiency of rolling diminishes. Heavier rollers will need to be employed to improve the efficiency of rolling when wicket soils have begun to dry out sufficiently to reduce the effects of lighter rollers. Only soils that have dried sufficiently, and therefore have enough strength, should be considered for heavier rolling. Weight-to-diameter considerations must be made on rollers to ensure that no steep bow waves are created on wickets. Careful consideration should also be given to rollers that have additional weights added, as this may also cause wicket damage.
As a general rule of thumb, initial
rolling should be with a roller that can be comfortably pushed by hand, gradually building up to something between one and two tonnes. Choosing the correct roller for the
correct soil conditions, when to start, and how much rolling should be done is, of course, an individual matter and personal preference, but I hope that this article has outlined some of the basic principles for those who are not so familiar with the technique.
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