18.4.5 Land Use Suitability
Land use suitability assessment was described in a 1976
report of the Food and Agriculture Organisation of the UN
http://www.fao.org/3/X5310E/x5310e00.htm#Contents.
Land use suitability assessment is allied to land use capability assessment as it also seeks to assess the suitability of a
tract of land for a range of potential land uses. Within an area
of study, a set of nominated land use types (LUT) are
delineated. A set of variables, usually known as ‘land
qualities’ or ‘soil qualities’ that will impact the performance
of LUTs across the study area are determined. This terminology should not be confused with that in the ‘soil quality’
analysis (Sect. 18.4.8). A key step is to determine the land
and soil variables that materially affect the performance of
the LUTs. For each LUT the relationship between land
quality, and the estimated LUT suitability class, is determined. The land qualities can be expressed in either continuous variables or classes.
A project called Topoclimate South, undertaken in
Southland from 1998 to 2001, was based on the land use
suitability method. The purpose of Topoclimate South was
to identify land for further regional investment in agriculture.
The project also delivered a sound basis for environmental
assessment and mitigation. Sam Carrick and the Topoclimate South soils team upgraded the regional soil classification and soil map of the Southland lowlands and low hill
country. The land use suitability analysis in Southland provides an example of the land use suitability assessment
process (Table 18.4). The Southland team assessed four land
use types: non-arable, arable, pastoral, and forestry. One of
the goals was to assess the versatility of the land, where
versatility relates to the range of crops that would be
assessed as suitable for a given land area.
Applications of land use suitability analysis are
wide-ranging and include:
• understanding of the effects of land and soil on the performance of specific land uses;
• determining favourable locations for specific enterprises;
• analysis of land use opportunities and risks;
• identification of indicators of soil resilience;
• determination of the level of versatility of land to support
a wide range of enterprises; and
• identification of the soil (class) and land character
required to support a particularly specialised enterprise.
18.4.6 Soil Versatility
The concept of soil versatility classification for arable land
was introduced in New Zealand by Les Molloy in 1980, and
based on two broad parameters: the physical characteristics
of the root zone, and climate zones. A highly versatile soil is
one that is capable of growing a wide range of crops suited
to its particular climate (essentially synonymous with ‘high
class’ soils (Sect. 18.4.11), or LUC class 1 and 2 soils,
(Sect. 18.4.4)). Thus, highly versatile soils occur on flat land
or very gentle slopes (<7°), have a potential rooting depth of
at least 0.9 m, offer little resistance to root penetration, and
suffer very few days per year of soil water deficit.
Versatility classifications were developed for arable crop
production and orchard crop production by Alistair Wilson
and Trevor Webb. Versatility indices provide the basis for
defining soil and land characteristics perceived to influence
crop production and soil management. Criteria used to assess
such characteristics include topography (land slope), soil
physical and chemical characteristics, environmental characteristics, and agro-climatic characteristics. For example,
agro-climatic characteristics include the duration of frost-free
periods (days), growing-degree days (November-April), chill
units, and sunshine hours, and these attributes are then
arranged into six classes (very high to extremely low) each
of which has a numerical rating 1–6 (1 being the optimum
rating, or the class with fewest agro-climatic limitations, and
6 the lowest rating).
An example of the derivation and use of soil versatility
classification is a study of the Conroy land system of Central
Otago undertaken by Allan Hewitt in 1995. The aims of the
study were to identify the most versatile land capable of
non-arable cropping that was irrigable, the least productive
land with little potential for productive use, and ‘other’ land
with limited productive potential but which may support
native plants or pasture. Versatility indices were estimated
by summing numerical suitability class assignments for irrigation, non-arable, arable, and pasture land uses, with the
lowest index being the most versatile soil. The most versatile
soils had versatility indices of 9. In contrast, soils with a
versatility index of 17 were identified as the least versatile
according to the parameters evaluated.
18.4.7 Soil Vulnerability
Soil vulnerability is a risk analysis that identifies possible
undesirable outcomes that may occur as a result of specific
soil properties. Commonly, the vulnerability is expressed in
qualitative terms. Soil process modelling may enable quantitative expression of risk. An example is the model
‘CLUES’ which assesses nitrate contamination risks and
pathways through the New Zealand landscape. The design
and implementation of CLUES were led by Sandy Elliot and
Graeme McBride. The model provides a spatial assessment
of the likelihood of nitrate contamination in groundwater and
surface water across the landscape.
18.4 Soil and Land Evaluation in New Zealand
301
Land use suitability assessment was described in a 1976
report of the Food and Agriculture Organisation of the UN
http://www.fao.org/3/X5310E/x5310e00.htm#Contents.
Land use suitability assessment is allied to land use capability assessment as it also seeks to assess the suitability of a
tract of land for a range of potential land uses. Within an area
of study, a set of nominated land use types (LUT) are
delineated. A set of variables, usually known as ‘land
qualities’ or ‘soil qualities’ that will impact the performance
of LUTs across the study area are determined. This terminology should not be confused with that in the ‘soil quality’
analysis (Sect. 18.4.8). A key step is to determine the land
and soil variables that materially affect the performance of
the LUTs. For each LUT the relationship between land
quality, and the estimated LUT suitability class, is determined. The land qualities can be expressed in either continuous variables or classes.
A project called Topoclimate South, undertaken in
Southland from 1998 to 2001, was based on the land use
suitability method. The purpose of Topoclimate South was
to identify land for further regional investment in agriculture.
The project also delivered a sound basis for environmental
assessment and mitigation. Sam Carrick and the Topoclimate South soils team upgraded the regional soil classification and soil map of the Southland lowlands and low hill
country. The land use suitability analysis in Southland provides an example of the land use suitability assessment
process (Table 18.4). The Southland team assessed four land
use types: non-arable, arable, pastoral, and forestry. One of
the goals was to assess the versatility of the land, where
versatility relates to the range of crops that would be
assessed as suitable for a given land area.
Applications of land use suitability analysis are
wide-ranging and include:
• understanding of the effects of land and soil on the performance of specific land uses;
• determining favourable locations for specific enterprises;
• analysis of land use opportunities and risks;
• identification of indicators of soil resilience;
• determination of the level of versatility of land to support
a wide range of enterprises; and
• identification of the soil (class) and land character
required to support a particularly specialised enterprise.
18.4.6 Soil Versatility
The concept of soil versatility classification for arable land
was introduced in New Zealand by Les Molloy in 1980, and
based on two broad parameters: the physical characteristics
of the root zone, and climate zones. A highly versatile soil is
one that is capable of growing a wide range of crops suited
to its particular climate (essentially synonymous with ‘high
class’ soils (Sect. 18.4.11), or LUC class 1 and 2 soils,
(Sect. 18.4.4)). Thus, highly versatile soils occur on flat land
or very gentle slopes (<7°), have a potential rooting depth of
at least 0.9 m, offer little resistance to root penetration, and
suffer very few days per year of soil water deficit.
Versatility classifications were developed for arable crop
production and orchard crop production by Alistair Wilson
and Trevor Webb. Versatility indices provide the basis for
defining soil and land characteristics perceived to influence
crop production and soil management. Criteria used to assess
such characteristics include topography (land slope), soil
physical and chemical characteristics, environmental characteristics, and agro-climatic characteristics. For example,
agro-climatic characteristics include the duration of frost-free
periods (days), growing-degree days (November-April), chill
units, and sunshine hours, and these attributes are then
arranged into six classes (very high to extremely low) each
of which has a numerical rating 1–6 (1 being the optimum
rating, or the class with fewest agro-climatic limitations, and
6 the lowest rating).
An example of the derivation and use of soil versatility
classification is a study of the Conroy land system of Central
Otago undertaken by Allan Hewitt in 1995. The aims of the
study were to identify the most versatile land capable of
non-arable cropping that was irrigable, the least productive
land with little potential for productive use, and ‘other’ land
with limited productive potential but which may support
native plants or pasture. Versatility indices were estimated
by summing numerical suitability class assignments for irrigation, non-arable, arable, and pasture land uses, with the
lowest index being the most versatile soil. The most versatile
soils had versatility indices of 9. In contrast, soils with a
versatility index of 17 were identified as the least versatile
according to the parameters evaluated.
18.4.7 Soil Vulnerability
Soil vulnerability is a risk analysis that identifies possible
undesirable outcomes that may occur as a result of specific
soil properties. Commonly, the vulnerability is expressed in
qualitative terms. Soil process modelling may enable quantitative expression of risk. An example is the model
‘CLUES’ which assesses nitrate contamination risks and
pathways through the New Zealand landscape. The design
and implementation of CLUES were led by Sandy Elliot and
Graeme McBride. The model provides a spatial assessment
of the likelihood of nitrate contamination in groundwater and
surface water across the landscape.
18.4 Soil and Land Evaluation in New Zealand
301