Tamar report land Capability Survey of Tasmania k e noble 1992 Tamar Report

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The levels of the land capability classification system are shown in Figure 2

1

2

3

4

5

6

7

Class

Subclass

Unit

erosion (e)

wetness (w)

soils (s)

climate (c)

1

2

3

etc

Degree of limitation

Dominant kind of limitation

Similar management and conservation requirements, etc

Figure 2: 

Levels of the land capability classification system.

(Adapted from: National Water and Soil Conservation Organisation, 1979, Our Land Resources.

(NWASCO), Wellington, New Zealand.)

References for Further Reading:

Dent, D. & Young, A., 1981, Soil Survey and Land Evaluation.  Allen and Unwin, London.

Gunn, R.H., Beattie, J.A., Reid, R.E. & van de Graaf, R.H.M., (eds) 1988, Australian Soil

and Land Survey Handbook: Guidelines for Conducting Surveys.  Inkata Press, Melbourne.

Hawkins, C.A., 1989, Agricultural Capability of Land, Tasmania.  A report on a suitable

system of capability classification and its application to the agricultural lands of the State.

Department of Primary Industry, Tasmania.

Klingebiel, A.A. & Montgomery, P.H., 1961, Land Capability Classification. Agriculture

Handbook No. 210. United States Department of Agriculture, Soil Conservation Service.

McRae, S.G. & Burnham, C.P., 1981, Land Evaluation. Oxford Science Publications,

Oxford.

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7. Features of the Tasmanian Land Capability

Classification System

7.1 The classification is based primarily upon three permanent biophysical features of the

landscape - soil, slope and climate, and their interactions.  These three factors have a

major influence in determining the capability of the land to produce agricultural goods.

Other factors which must be taken into account are rock type, erosion hazard, range of

crops that can be grown, management practices, soil conservation treatment, risk of

flooding and past land use history.

7.2 The classification comprises seven classes ranked in order of increasing degree of

limitations to use, and in decreasing order of versatility of use.

7.3 This survey only subdivides land to the class level.  Further subdivision of land below

the class level would be possible at more detailed scales of mapping, and would group

together similar types of land requiring the same kind of management, the same kind

and intensity of conservation treatments, and which occur on soils which are adapted to

the same kinds of crops, with similar potential yields.

7.4 The system is hierarchical.  Class 1 land can produce a wider variety of crops and

pastures at higher levels of production with lower costs, or with less risk of damage to

the land, than any of the other classes of land.  Class 2 land is similarly superior to

classes 3 to 7, and so on.

7.5 The system assesses the versatility of the land to produce a range of agricultural goods

that are considered typical for Tasmania, and not just those that are specific or suited to

localised areas.  For example, the range of crops that can be grown on classes 1 and 2

land would be wider than the range of crops grown on classes 3 and 4 land; and would

include vegetable and allied crops, orchards as well as cereals, essential oils and forage

crops.

7.6 The classification takes into account physical limitations the land may have.

Limitations may be defined as physical factors or constraints which affect the

versatility of the land and determine its capability for long-term sustainable

agricultural production.  The capability class takes into account the kind and degree of

limitations present.

Examples of different kinds of limitations are: erosion hazard, slope, climate, flooding,

stoniness, rock outcrops, salinity, poor soil structure, poor internal drainage, low

fertility and low soil moisture holding capacity.  There may be one or a number of

limitations present at any one site, but it is the overall degree of limitation present that

determines the capability class.

Physical limitations can be classified as either permanent, or able to be removed or

modified.  Permanent limitations include slope and most climatic influences.

Removable or modifiable limitations include flooding, poor drainage, and the  presence

of stones.  In addition, some climatic effects such as wind and low rainfall can be

modified by the installation of shelterbelts and irrigation.  The feasibility of the

removal of a limitation depends largely on the severity of the limitation, and also on

economics.  Guidelines are therefore necessary to differentiate between limitations that

can be reasonably removed and those that cannot.

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15

Although economics do not feature in land capability assessments, they are a significant

consideration when the removal of limitations is contemplated.  The following key words:

reasonable, feasible, and economic, are considered when deciding if limitations could be

modified or removed. Limitations that are assumed to be removable using existing

technology on an individual farm basis include poor drainage, stoniness, and low fertility.

Where the necessary technology is not a practical proposition, or beyond the capabilities of

an individual farmer and requires a catchment or community scheme, the land is classified

according to the nature of its present limitations. If in time such schemes become operative,

the land can be reclassified (if appropriate) into a higher land capability class.

Many areas have the potential to attain an improved land capability ranking through the

application of irrigation.  The extent of the beneficial effects of irrigation on land capability

will vary considerably, depending upon such factors as available water and economics,

which require individual assessment on a property basis.  However it is not possible to

provide a uniform system of classification of land capability based on irrigation potential

on an on-farm basis, so this has not been included in the assessment of capability.  In

addition, areas within regional irrigation schemes (such as Cressy/Longford, Winnaleah

and Coal River) may have a higher land capability ranking than that shown on the map.

However because the effect of an irrigation scheme on land capability depends on a number

of factors including economics, availability of water and type of irrigation used, the fact

that an area falls within the boundary of a designated irrigation scheme has not influenced

its capability in this study.  Therefore land capability has been assessed assuming no

irrigation potential.

With drainage, the land capability is considered assuming that drainage techniques that are

currently available within the scope of an `average' farmer to install, have been installed.

These would include maintenance of existing drainage lines on individual properties, and

installation of basic drainage measures to remove excess surface water.  The installation of

a large scale drainage scheme or extensive underground drainage, is not considered to be

within the scope of individual farmers.

The land capability of areas that fall within Drainage Trust Schemes (e.g. Dairy Plains,

King Island, Flinders Island, Mowbray Swamp and Circular Head) has been assessed

according to the present condition of the land.  In other words, the fact that an area of land

falls within the boundary of a Drainage Trust Scheme has not influenced the land capability

ranking.  This is mainly because not all areas of land within Drainage Trusts are capable of

the same increased land capability ranking, and not all areas within the Trust boundaries

have been effectively drained to date.

Maps of both Irrigation Scheme areas and Drainage Trust areas will be incorporated into

the relevant reports.

Climate is one of the major permanent limitations that restrict the versatility of the land

(particularly for cropping), and together with soil and slope, has a major influence in

determining the land capability class.

For a land capability survey at this scale (1:100 000) only generalised statements and

boundaries relating to climate can be made.  At more detailed scales of mapping, climatic

boundaries (as they affect land capability) can be more clearly defined.  These would be

based on more localised effects of topography (including aspect), reliability of rainfall,

availability of irrigation water, and more detailed records of rainfall, frosts, wind, etc.

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