foot track because it tends to result in more placid pitches’
(NZ Herald 14/3/2010).
The Waikari and Kakanui clays are both from dark
blackish coloured Melanic Soils. The Melanic Soils are
commonly derived from limestone or marble parent materials and contain smectite clays (notably montmorillonite,
which has a large shrink-swell range) that shrink and swell
strongly on wetting and drying. The advantage is that, once
dry, water can be moved quickly into the soil through the
cracks that form allowing rewetting from depth. The Waikari
clay is preferred for one-day games but it will tend to crack
more during drying in longer games.
The soils in the major rugby stadiums, such as the Waikato Stadium and the ‘Cake Tin’ in Wellington, are constructed and designed for purpose. The days of the All
Blacks and opponents wading through a ‘sea of mud’ are
long gone and the pressure is on to have a perfect looking
green turf, for the TV cameras, that will stand the heavy
trampling of rugby players, coatings of paint from sponsors
messages, and not lead to any condition of surface roughness
or slipperiness that could lead to the injury of an expensive
professional player.
For example, the Waikato stadium ‘soil’ consists of sand
that has been mixed with a plastic binding material with a
subsurface drainage system and a ‘pop-up’ irrigation system.
This provides a free draining medium for grass growth. The
sand has minimal water or nutrient holding capacity and so
the grass is grown with regular additions of water and fertiliser, including generous use of nitrogen, a system akin to
hydroponics.
Cricket pitch construction—why bother with the
grass?
New Zealand Cricket suggests that a good cricket
pitch should produce consistent ‘pace and bounce’ of
the ball and to do this needs minimal soil organic
matter, no soil layering, good compaction, and even
grass cover. The even grass cover should comprise
very short grass, pressed onto the ground surface with
the clay visible through it. There should be no weeds
and the bare soil should not exceed 15% of the surface
with no bare spot greater than 2 cm in diameter. These
requirements mean that the grass is ‘decimated’ during
the final pitch preparation. This begs the question—
why bother with grass at all? Grass is important to
cricket pitch preparations as a healthy plant root system helps achieve even drying of the pitch to depth.
Without grass, removal of water via surface evaporation can lead to steep moisture gradients and inconsistent surface cracking. The plant roots, and rolled in
surface turf, help hold the pitch together. However, a
buildup of organic material in the soil is not wanted.
Grass cover helps create ‘pace’ and consistency in
how the ball behaves and can also protect the ball from
wear. It is a tribute to the resilience of grass that it can
withstand the conditions in which it is asked to grow
on cricket pitches—where moisture contents are
allowed to go extremely low, soil dry bulk densities
are exceedingly high, and the grass is cut to 12–
15 mm throughout the playing season and as low as
3 mm on playing day.
3.4 Distinguishing Between Anthropic Soils
and Related Soil Orders
Land use practices can have strong effects on natural soils.
Over the last 50 years or more, land development operations, such as deep ploughing, have caused deep soil mixing.
The construction of mid-twentieth century border-dyke irrigation systems resulted in scalping of topsoils and soil
relocation over short distances. Historically, there have also
been changes made to soil by cutting and burning of native
bush for pasture establishment, fertilisation, and seeding,
especially by the aerial topdressing industry, leading to
widespread changes in soil chemical properties. The question may be asked—have the changes wrought by these
management interventions produced Anthropic Soils? It has
not been the practice to consider such altered soils as
Anthropic Soils. Where then do we draw the line between
modified soils and Anthropic Soils?
The boundary between Anthropic and other soil orders
depends of the nature of the changes. For a soil to be considered an Anthropic Soil, it must be so severely changed
from its original state that its prior order cannot be positively
identified using the New Zealand Soil Classification key to
soil orders. Thus the Anthropic Soils are placed third-to-last
in the key (ahead of only Recent and Raw Soils).
For all of the soil orders other than Anthropic Soils
identification relies on objective soil properties (presence or
absence of diagnostic horizons and features of designated
thickness and placement in the profile, the ‘control section’),
but the identification of the diverse range of Anthropic Soils
inevitably involves historical research and inferences from
apparent changes in landforms, as well as direct soil observations. The critical observations include the presence or
absence of the normal natural soil profiles and soil horizons
expected in the area, and the interpretation of any
non-normal soil features.
Raw Soils and Recent Soils can potentially be confused
with Anthropic Soils, especially where there is evidence of
thick burial of a soil by young sediment. An interesting
example of this dilemma is the ‘German’ soil series
3.3 Key Soil Properties
51
(NZ Herald 14/3/2010).
The Waikari and Kakanui clays are both from dark
blackish coloured Melanic Soils. The Melanic Soils are
commonly derived from limestone or marble parent materials and contain smectite clays (notably montmorillonite,
which has a large shrink-swell range) that shrink and swell
strongly on wetting and drying. The advantage is that, once
dry, water can be moved quickly into the soil through the
cracks that form allowing rewetting from depth. The Waikari
clay is preferred for one-day games but it will tend to crack
more during drying in longer games.
The soils in the major rugby stadiums, such as the Waikato Stadium and the ‘Cake Tin’ in Wellington, are constructed and designed for purpose. The days of the All
Blacks and opponents wading through a ‘sea of mud’ are
long gone and the pressure is on to have a perfect looking
green turf, for the TV cameras, that will stand the heavy
trampling of rugby players, coatings of paint from sponsors
messages, and not lead to any condition of surface roughness
or slipperiness that could lead to the injury of an expensive
professional player.
For example, the Waikato stadium ‘soil’ consists of sand
that has been mixed with a plastic binding material with a
subsurface drainage system and a ‘pop-up’ irrigation system.
This provides a free draining medium for grass growth. The
sand has minimal water or nutrient holding capacity and so
the grass is grown with regular additions of water and fertiliser, including generous use of nitrogen, a system akin to
hydroponics.
Cricket pitch construction—why bother with the
grass?
New Zealand Cricket suggests that a good cricket
pitch should produce consistent ‘pace and bounce’ of
the ball and to do this needs minimal soil organic
matter, no soil layering, good compaction, and even
grass cover. The even grass cover should comprise
very short grass, pressed onto the ground surface with
the clay visible through it. There should be no weeds
and the bare soil should not exceed 15% of the surface
with no bare spot greater than 2 cm in diameter. These
requirements mean that the grass is ‘decimated’ during
the final pitch preparation. This begs the question—
why bother with grass at all? Grass is important to
cricket pitch preparations as a healthy plant root system helps achieve even drying of the pitch to depth.
Without grass, removal of water via surface evaporation can lead to steep moisture gradients and inconsistent surface cracking. The plant roots, and rolled in
surface turf, help hold the pitch together. However, a
buildup of organic material in the soil is not wanted.
Grass cover helps create ‘pace’ and consistency in
how the ball behaves and can also protect the ball from
wear. It is a tribute to the resilience of grass that it can
withstand the conditions in which it is asked to grow
on cricket pitches—where moisture contents are
allowed to go extremely low, soil dry bulk densities
are exceedingly high, and the grass is cut to 12–
15 mm throughout the playing season and as low as
3 mm on playing day.
3.4 Distinguishing Between Anthropic Soils
and Related Soil Orders
Land use practices can have strong effects on natural soils.
Over the last 50 years or more, land development operations, such as deep ploughing, have caused deep soil mixing.
The construction of mid-twentieth century border-dyke irrigation systems resulted in scalping of topsoils and soil
relocation over short distances. Historically, there have also
been changes made to soil by cutting and burning of native
bush for pasture establishment, fertilisation, and seeding,
especially by the aerial topdressing industry, leading to
widespread changes in soil chemical properties. The question may be asked—have the changes wrought by these
management interventions produced Anthropic Soils? It has
not been the practice to consider such altered soils as
Anthropic Soils. Where then do we draw the line between
modified soils and Anthropic Soils?
The boundary between Anthropic and other soil orders
depends of the nature of the changes. For a soil to be considered an Anthropic Soil, it must be so severely changed
from its original state that its prior order cannot be positively
identified using the New Zealand Soil Classification key to
soil orders. Thus the Anthropic Soils are placed third-to-last
in the key (ahead of only Recent and Raw Soils).
For all of the soil orders other than Anthropic Soils
identification relies on objective soil properties (presence or
absence of diagnostic horizons and features of designated
thickness and placement in the profile, the ‘control section’),
but the identification of the diverse range of Anthropic Soils
inevitably involves historical research and inferences from
apparent changes in landforms, as well as direct soil observations. The critical observations include the presence or
absence of the normal natural soil profiles and soil horizons
expected in the area, and the interpretation of any
non-normal soil features.
Raw Soils and Recent Soils can potentially be confused
with Anthropic Soils, especially where there is evidence of
thick burial of a soil by young sediment. An interesting
example of this dilemma is the ‘German’ soil series
3.3 Key Soil Properties
51