WHAT CAUSES ROOT BREAKS?
Root breaks are a complex feature of cricket pitch. Root breaks can occur at any depth within the
profile but the nearer the surface they are, the more likely they are to affect ball bounce. As the
layer forms, grass root growth exploits the large void created and tends to grow horizontally (Figure
1). This creates a shock absorbing layer that reduces the ball energy on impact and slows the pace
and bounce of the pitch. It also will vary across the pitch, making it more variable.
Figure 1 The effect of root breaks in cricket pitch profiles on grass growth. The root break provides a low
resistance path for grass roots to grow when compared to the compacted soil below.
Root breaks are caused by a combination of factors including:
1. The construction of pitches in layers
Typically pitches are constructed in compacted layers of 50 mm. If the next layer is not
keyed into the previous layer by raking or scarifying the surface of the lower layer then
breaks at 50 mm will be manufactured into the profile. Even when constructed in 50 mm
layers the top of the 50 mm layer will be more compacted than the soil below so careful
construction is essential.
2. Topdressing with incompatible soil loams
It is essential that any topdressing or reconstruction work uses the same loam as soils lower
in the profile, otherwise they could shrink and swell at different rates which could lead to a
fissure developing between soil layers.
3. Natural shrink-swell behaviour
The clay loam soils used for cricket pitches shrink and swell and they do this more nearer the
surface because there is less overburden from other soil above confining the shrink and
swell. Without careful rolling to maintain near surface compaction, significant differences in
density can occur.
4. Rolling when the soil is too wet
The Cranfield University research on rolling (www.cranfield.ac.uk/sas/sst/rolling) showed
that roller can move the soil backwards and forwards as well as downwards during rolling.
This horizontal stress on the soil can cause soil in the top 50 mm to move relative to the soil
below when the soil is too wet. This is particularly a problem with heavy, small-diameter
rollers (diameters < 500 mm). Rolling in the right conditions is essential to prevent this
damage.
5. Root growth impedance in high density soils
The effect of compaction on root growth is shown in Error! Reference source not found. and
Error! Reference source not found. which show how high density soil causes shallow rooting
and a near-surface reduction in density. The grass itself creates a layer as it loosens the soil.
6. Shallow aeration practices
Cultivating the soil near the surface to make shallow slits and spike holes can create a loose
layer over a more compacted deeper layer. This is then exploited by the grass roots,
creating a break.
In reality it is likely to be a combination of these factors that lead to the formation of a break but
pitch construction and the use of the correct soils is essential in limiting their development.
Strategies for addressing root breaks vary with the depth of the root break, the extent of the root
break across the pitch/square and the available budget.
Return to: HOW DO PROFILES AFFECT GRASS GROWTH?
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