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2.1 General
2.2 Land
2.3 Land use
2.4 Land characteristics, land qualities and diagnostic criteria
2.5 Requirements and limitations
2.6 Land improvements
2.7 Land suitability and land capability
Certain concepts and definitions areneeded as a basis for the subsequent discussion. These concern the land itself, kinds ofland use, land characteristics and qualities, and improvements made to land.
For the sake of clarity, somedefinitions are given in the text in simplified form. Formal definitions of terms used ina specialized sense are given in the Glossary.
Land comprises the physicalenvironment, including climate, relief, soils, hydrology and vegetation, to the extentthat these influence potential for land use. It includes the results of past and presenthuman activity, e.g. reclamation from the sea, vegetation clearance, and also adverseresults, e.g. soil salinization. Purely economic and social characteristics, however, arenot included in the concept of land; these form part of the economic and social context.
A land mapping unit is amapped area of land with specified characteristics. Land mapping units are defined andmapped by natural resource surveys, e.g. soil survey, forest inventory. Their degree ofhom*ogeneity or of internal variation varies with the scale and intensity of the study. Insome cases a single land mapping unit may include two or more distinct types of land, withdifferent suitabilities, e.g. a river flood plain, mapped as a single unit but known tocontain both well-drained alluvial areas and swampy depressions.
Land is thus a wider concept thansoil or terrain. Variation in soils, or soils and landforms, is often the main cause ofdifferences between land mapping units within a local area: it is for this reason thatsoil surveys are sometimes the main basis for definition of land mapping units. However,the fitness of soils for land use cannot be assessed in isolation from other aspects ofthe environment, and hence it is land which is employed as the basis for suitabilityevaluation.
Suitability evaluation involvesrelating land mapping units to specified types of land use. The types of use consideredare limited to those which appear to be relevant under general physical, economic andsocial conditions prevailing in an area. These kinds of land use serve as the subject ofland evaluation. They may consist of major kinds of land use or land utilization types.
2.3.1 Major Kinds of Land Useand Land Utilization Types
A major kind of land use is amajor subdivision of rural land use, such as rainfed agriculture, irrigated agriculture,grassland, forestry, or recreation. Major kinds of land use are usually considered in landevaluation studies of a qualitative or reconnaissance nature.
A land utilization type is akind of land use described or defined in a degree of detail greater than that of A majorkind of land use. In detailed or quantitative land evaluation studies, the kinds of landuse considered will usually consist of land utilization types. They are described with asmuch detail and precision as the purpose requires. Thus land utilization typos are not acategorical level in a classification of land use, but refer to any defined use below thelevel of the major kind of land use.
A land utilization typo consists ofa set of technical specifications in a given physical, economic and social setting. Thismay be the current environment or a future Betting modified by major land improvement e,e.g. an irrigation and drainage scheme. Attributes of land utilization types include dataor assumptions on:
- Produce, including goods (e.g. crops, livestock timber), cervices (e.g. recreational facilities) or other benefits (e.g. wildlife conservation)
- Market orientation, including whether towards subsistence or commercial production
- Capital intensity
- Labour intensity
See AlsoLand And Its Types - ClassNotes.ngLand Use Type Definition | Law InsiderWhat Is Land? Definition in Business, Valuation, and Main UsesLand Facts for Kids- Power sources (e.g. man's labour, draught animals machinery using fuels)
- Technical knowledge and attitudes of land users
- Technology employed (e.g. implements and machinery, fertilizers, livestock breeds, farm transport, methods of timber felling)
- Infrastructure requirements (e.g. sawmills, tat factories, agricultural advisory services)
- Size and configuration of land holdings, including whether consolidated or fragmented
- Land tenure, the legal or customary manner in which rights to land are held, by individuals or groups
- Income levels, expressed per capita, per unit of production (e.g. farm) or per unit area.
Management practices on differentareas within one land utilization typo are not necessarily the same. For example, the landutilization type may consist of mixed farming, with part of the land under arable use andpart allocated to grazing. Such differences may arise from variation in the land, from therequirements of the management system, or both.
Some examples of land utilizationtypes are:
i. Rainfed annual cropping based on groundnuts with subsistence maize, by smallholders with low capital resources, using cattle drawn farm implements, with high labour intensity, on freehold farms of 5-10 ha.
ii. Farming similar to (i) in respect of production, capital, labour, power and technology, but farms of 200-500 ha operated on a communal basis.
iii. Commercial wheat production on large freehold farms, with high capital and low labour intensity, and a high level of mechanization and inputs.
iv. Extensive cattle ranching, with medium levels of capital and labour intensity, with land held and central services operated by a governmental agency.
v. Softwood plantations operated by a government Department of Forestry, with high capital intensity, low labour intensity, and advanced technology.
vi. A national park for recreation and tourism.
Some descriptions of land utilization types are given in Chapter 5.
Where it is wished to relateagricultural land utilization types to a general classification, the Typology of WorldAgriculture of the International Geographical Union may be considered (Kostrowicki, 1974).The role of land utilization types in land evaluation is discussed further in Beek (1975).
2.3.2 Multiple and CompoundLand Use
Two terms, multiple and compoundland utilization types, refer to situations in which more than one kind of land use ispracticed within an area.
A multiple land utilization typeconsists of more than one kind of use simultaneously undertaken on the same area of land,each use having its own inputs, requirements and produce. in example is a timberplantation used simultaneously as a recreational area.
A compound land utilization typeconsists of more than one kind of use undertaken on areas of. land which for purposes ofevaluation are treated as a single unit. The different kinds of use may occur in timesequence (e.g. as in crop rotation) or simultaneously on different areas of land withinthe same organizational unit. Mixed farming involving both arable use and grazing is anexample.
Sometimes an appropriate landutilization type can be found by making several land mapping units part of the samemanagement unit, e.g. livestock management which combines grazing on uplands in the rainyseason and on seasonally flooded lowlands in the dry season.
Land utilization types are definedfor the purpose of land evaluation. Their description need not comprise the full range offarm management practices, but only those related to land management and improvement. Atdetailed levels of evaluation, closely-defined land utilization types can be extended intofarming systems by adding other aspects of farm management. Conversely, farming systemsthat have already bean studied and described can be adopted as the basis for landutilization types.
2.4 Land characteristics, land qualities and diagnosticcriteria
A land characteristic is anattribute of land that can be measured or estimated. Examples are slope angle, rainfall,soil texture, available water capacity, biomass of the vegetation, etc. Land mappingunits, as determined by resource surveys, are normally described in terms of landcharacteristics.
If land characteristics are employeddirectly in evaluation, problems arise from the interaction between characteristics. Forexample, the hazard of soil erosion is determined not by slope angle alone but by theinteraction between elope angle, slope length, permeability, soil structure, rainfallintensity and other characteristics. Because of this problem of interaction, it isrecommended that the comparison of land with land use should be carried out in terms ofland qualities.
A land quality is a complexattribute of land which acts in a distinct manner in its influence on the suitability ofland for a specific kind of use. Land qualities may be expressed in a positive or negativeway. Examples are moisture availability, erosion resistance, flooding hazard, nutritivevalue of pastures, accessibility. Where data are available, aggregate land qualities mayalso be employed, e.g. crop yields, mean annual increments of timber species.
Table 1 gives an illustrative listof land qualities related to productivity from three kinds of use and to management andinputs. It is not exhaustive, nor is each land quality necessarily relevant for aparticular area and type of land use. The qualities listed in B and C are in addition tothose of A, which may be relevant to all three kinds of use (based in part on Beek andBennema, 1972). There may also be land qualities related to major land improvements. Thesevary widely with the types of improvement under consideration. An example is landevaluation in relation to available supplies of water where irrigation is beingconsidered.
A land quality is not necessarilyrestricted in its influence to one kind of use. The same quality may affect, for example,both arable use and animal product
There are a very large number ofland qualities, but only those relevant to land use alternatives under consideration needbe determined. A land quality is relevant to a given type of land use if it influenceseither the level of inputs required, or the magnitude of benefits obtained, or both. Forexample, capacity to retain fertilizers is a land quality relevant to most forms ofa*griculture, and one which influences both fertilizer inputs and crop yield. Erosionresistance affects the costs of soil conservation works required for arable use, whilstthe nutritive value of pastures affects the productivity of land under ranching.
Land qualities can sometimes beestimated or measured directly, but are frequently described by means of landcharacteristics. Qualities or characteristics employed to determine limits of landsuitability classes or subclasses are known as diagnostic criteria.
A diagnostic criterion is avariable which has an understood influence upon the output from, or the required inputsto, a specified use, and which serves as a basis for assessing the suitability of a givenarea of land for that use. This variable may be a land quality, a land characteristic, ora function of several land characteristics. For every diagnostic criterion there will be acritical value or set of critical values which are used to define suitability classlimits.
Table 1 EXAMPLES OF LANDQUALITIES
A. LAND QUALITIES RELATED TOPRODUCTIVITY FROM CROPS OR OTHER PLANT GROWTH
- Crop yields (a resultant of many qualities listed below)
- Moisture availability
- Nutrient availability
- Oxygen availability in the root zone
- Adequacy of foothold for roots
- Conditions for germination
- Workability of the land (ease of cultivation)
- Salinity or alkalinity
- Soil toxicity
- Resistance to soil erosion
- Pests and diseases related to the land
- Flooding hazard (including frequency, periods of inundation)
- Temperature regime
- Radiation energy and photoperiod
- Climatic hazards affecting plant growth (including wind, hail, frost)
- Air humidity as affecting plant growth
- Drying periods for ripening of crops.
B. LAND QUALITIES RELATED TODOMESTIC ANIMAL PRODUCTIVITY
- Productivity of grazing land (a resultant of many qualities listed under A.)
- Climatic hardships affecting animals
- Endemic pests and diseases
- Nutritive value of grazing land
- Toxicity of grazing land
- Resistance to degradation of vegetation
- Resistance to soil erosion under grazing conditions
- Availability of drinking water.
C. LAND QUALITIES RELATED TO FORESTPRODUCTIVITY
The qualities listed may refer tonatural forests, forestry plantations, or both.
- Mean annual increments of timber species (a resultant of many qualities listed under A.)
- Types and quantities of indigenous timber species
- Site factors affecting establishment of young trees
- Pests and diseases
- Fire hazard.
D. LAND QUALITIES RELATED TOMANAGEMENT AND INPUTS
The qualities listed may refer toarable use, animal production or forestry.
- Terrain factors affecting mechanization (trafficability)
- Terrain factors affecting construction and maintenance of access roads (accessibility
- Size of potential management units (e.g. forest blocks, farms, fields
- Location in relation to markets and to supplies of inputs.
2.4.1 Examples
These terms may be illustrated withreference to the land quality "oxygen availability in the root zone". Thisquality can be most closely estimated by the diagnostic criterion of the period when theredox potential (Eh) in the root zone is less than +200 millivolts. Such information wouldfrequently not be available, in which case the next most direct criterion would be periodswhen the root zone lay below the water table. For example, oxygen availability might beclassed as "moderate" with 3-6 months below the water table, and "low"with over 6 months. Failing information on periods with a high water table, then soilmottling, soil drainage class or natural vegetation could be used as diagnostic criteriafor assessing oxygen availability.
Land qualities can sometimes bedescribed by means of a single land characteristic, as in the preceding example. In manycases, however, their rating involves combinations of several characteristics, as in thecase of moisture availability illustrated by the following example.
Moisture availability to plants is aland quality that is relevant in a wide variety of circ*mstances. It can apply to arablecropping, animal productivity (via its influence on growth of pastures) and forestproduction. It can affect both productivity, e.g. crop yields, and inputs, e.g. mulchingmeasures necessary, or amounts of irrigation water required. Among the landcharacteristics which affect the quality moisture availability are: amount of rainfall,its seasonal distribution and variability; potential evapotranspiration, and hence thecharacteristics which themselves affect it (temperature, humidity, wind speed, etc.); andavailable water capacity of the soil, and the characteristics which affect it - effectivesoil depth (depth to which roots penetrate) and the field capacity and wilting point ofeach soil horizon, the latter being in turn influenced by texture, organic matter content,etc. The probable recurrence interval at which the soil moisture level falls to wiltingpoint within the entire rooting zone is a further land characteristic of importance (whichcan be estimated but not measured within a short period). By no means all these landcharacteristics would be employed as diagnostic criteria. Supposing, for example, thatdifferences in both rainfall and potential evapotranspiration within the surveyed areawere so small as to be of little importance in differentiating types of land, then thischaracteristic would become part of the physical context of the evaluation and would notbe used in defining class limits. The most appropriate diagnostic criterion used to defineclass limits might be available water capacity of the soil profile. However, where soildata were not available, then some function of effective depth and soil texture, believedto bear a linear relationship with available water capacity, could be used. In the formercase, the set of critical values for available water capacity used to define class limitsmight be such as: over 40 cm, 30 40 cm, 24-30 cm.
2.4.2 The Scarcity Value ofLand
The value of a particular type ofland may be increased by its scarcity or the rarity of certain of its qualities, within agiven region or country. This is often the position with nature reserves. In the extremecase, the presence of a plant or animal species unique to one area may make that landvirtually irreplaceable, resulting in strict protection even against highly profitableother uses. Situations whor* land acquires added suitability for a particular use byvirtue of its scarcity can also arise with productive forms of uses for example wheredry-season grazing land is in short supply.
2.5Requirements and limitations
Requirements of the land userefer to the set of land qualities that determine the production and management conditionsof a kind of land use.
Limitations are landqualities, or their expression by means of diagnostic criteria, which adversely affect akind of land use.
For example, the requirements formechanized cultivation of wheat include high availability of oxygen in the root zone andabsence of obstructions (boulders or rock outcrops); waterlogging and the presence ofboulders are limitations. Thus limitations may be regarded as land qualities expressed insuch a way as to show the extent to which the conditions of the land fall short of therequirements for a given use.
Land improvements areactivities which cause beneficial changes in the qualities of the land itself. Landimprovements should be distinguished from improvements in land use, i.e. changes in theuse to which the land is put or modifications to management practices under a given use.
Land improvements are classed asmajor or minor. A major land improvement is a substantial and reasonably permanentimprovement in the qualities of the land affecting a given use. A large non-recurrentinput is required, usually taking the form of capital expenditure on structure andequipment. Once accomplished, maintenance of the improvement remains as a continuing cost,but the land itself is more suitable for the use than formerly. Examples are largeirrigation schemes drainage of swamps and reclamation of salinized land.
A minor land improvement isone which either has relatively small effects or is non-permanent or both, or which lieswithin the capacity of individual farmers or other land users. Stone clearance,eradication of persistent weeds and field drainage by ditches are examples.
The separation of major from minorland improvements is intended only as an aid to making a suitability classification. Thedistinction is a relative one; it is not clear-cut and is only valid within a localcontext. In cases of doubt, the main criterion is whether the improvement is within thetechnical and financial capacity of individual farmers or other landowners (includingsmall communal owners, e.g. village co-operatives). In many areas improvements such assubsoiling, dynamiting or terracing cannot be undertaken by individual farmers, and aretherefore regarded as major land improvements; in countries with large farms and highcapital resources coupled with good credit facilities, however, these changes may bewithin reach of individuals and are therefore considered as minor improvements. Fielddrainage is another improvement that may or may not be regarded as major, depending onfarm size, permanency of tenure, capital availability and level of technology.
2.7 Land suitability and land capability
The term "land capability"is used in a number of land classification systems, notably that of the Soil ConservationService of the U.S. Department of Agriculture (Klingebiel and Montgomery, 1961). In theUSDA system, soil mapping units are grouped primarily on the basis of their capability toproduce common cultivated crops And pasture plants without deterioration over a longperiod of time. Capability is viewed by some as the inherent capacity of land to performat a given level for a general use, and suitability as a statement of the adaptability ofa given area for a specific kind of land use; others see capability as a classification ofland primarily in relation to degradation hazards, whilst some regard the terms"suitability" and "capability" as interchangeable.
Because of these varyinginterpretations, coupled with the long-standing association of "capability" withthe USDA system, the term land suitability is used in this framework, and no furtherreference to capability is made.
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