SOIL AND LAND CLASSIFICATION
PART II
By Dr. Sumihar Hutapea, MS/ Indah Apriliya, SP. M.Si
13th Meeting
SOIL SURVEY
“The practical purpose of soil survey is to enable more numerous, more accurate and more useful predictions [of land performance] to be made for specific purposes than could have been made otherwise [i.e., in the absence of
location-specific information about soils]. (Dent and young, 1981)”
Why is it necessary to conduct a survey and evaluation of land
resources?
Two types of soil/land survey by objective:
1. Scientific, to understand the soil as a natural body in the landscape:
• Soil genesis studies
• Study of specific properties in
relation to soil-forming factors, etc.
2. Utilitarian, to answer specific
questions about the response of land
to land use
Utilitarian Survey of Land resource means:
First, survey should be demand-driven, and that methods and products can be specified according to demand and budget
Second, we can use objective criteria to see if it has met certain specifications.
Third, must serve society or private interests directly, i.e. soil survey must be a cost-effective way of improving the
overall wealth or well-being of society or some segment
thereof (e.g., individual, landowner or land user).
Soil Survey
What do we actually map in ‘soil’ survey?
(1) Land conditions
● Soil itself; landform; surface conditions (e.g. stones); groundwater & surface water regime; substratum; current land use; climate.
● Obviously more useful than just soil
● Problem: (1) more difficult; (2) some boundaries may not coincide, we may get many small map units. This can be avoided to some extent by using physiographic mapping units.
(2) Soil only
● Only the soil properties, according to some definition of ‘soil’. But this leaves out many important characteristics that influence land use and which are easily seen and mapped by the soil surveyor. Areas of ‘non-soil’ are
delineated but not characterized.
(3) Soil & intimately-associated surface conditions
● In practice this is the most common ‘soil’ map. Phases of soil map units include slope, micro-relief form, stoniness…
Soil and other natural resource surveys vary in publication map scale, intensity of observations, and techniques. These tend to co-vary.
(1) What is the intensity of the survey (density of observations) and what is the method by which observations are made?
(2) What is the range of properties (or, the degree of homogeneity) of the mapping units?
(3) What are the names of the mapping units?
(4) What is the purpose of the survey? I.e., what interpretations will be made from it?
Pendekatan sintetik dan analitik
When we try to divide the landscape up into units, there are two fundamental approaches: synthetic and analytic.
Pendekatan Sintetik, make observations, and then try to group them so that the resulting map units separate as much of the variability as possible. The ‘synthesis’ is the forming of spatial units from point observations. In summary:
1. Make a set of point observations;
2. Group them into map units so that inter-unit variability is maximized, and intra-unit variability is minimized.
Pendekatan analitik, first separate the landscape into ‘natural’ soil bodies, using external characteristics such as landform, vegetation, and surface soil, and then characterize the resulting units by sampling. The ‘analysis’ is the separation of
‘natural’ soil bodies based on external clues. In summary:
1. Divide the landscape into components such that we expect that they will have different soils;
2. Characterize the resulting units by sampling.
Survey Method
Survey Method
Lereng sangat curam / terjal (kemiringan > 45 %)
Agak curam
(kemiringan 15 - 30 %) Lereng datar
(kemiringan 0 - 3 %)
LAND CAPABILITY
AND SUITABILITY
STEPS
Land Survey
Land Evaluation
Land Capability and Suitability
Landuse Planning
Capability Class
● Land capability is defined as the inherent capacity of land to be productive under sustained use and specific management methods
● Land capability classification is grouping and grading of soils according to potential and limitation, capacity for producing agricultural crops.
● In capability system, soils are generally grouped at three levels-capability class, subclass, and unit.
Capability Class
● Capability classes, the broadest groups, are designated by the number 1 through 8.
● The numbers indicate progressively greater limitations and narrower choices for practical use.
● Class I : soils have slight limitations that restrict their use
● Class II : soils have moderate limitations that restrict the choice of plants or that require moderate conservation practice.
● Class III : soils have severe limitations that restrict the choice of plants or that require special conservation practices
● Class IV : soils have very severe limitations that restrict the choice of plants or that require very careful management, or both.
Capability Class
● Class V : soils are subject to little or no erosion but have other limitations, impractical to remove, that restrict their use mainly to pasture, or forestland.
● Class VI : soils have severe limitations that make them generally unsuitable for cultivation and that restrict their use mainly to pasture, forestland, and wildlife habitat.
● Class VII: soils have very severe limitations that make them unsuitable for
cultivation and that restrict their use mainly to grazing, forestland, wildlife habitat.
● Class VIII : soils have limitations that preclude commercial plant production and that restrict their use to recreational purposes, wildlife habitat, watershed, or aestethic purposes.
Capability Subclass
● Capability subclasses are soil groups within one class
● They are designated by adding a small letter :
e : erosion (bahaya erosi)
w: water (genangan/kelebihan air)
s : plant roots (penghambat terhadap perakaran tanaman)
c : climate (suhu dan curah hujan)
● Example : 2e
Capability Units
● Capability units are soil groups within a subclass
● The soils in a capability unit are enough alike to be suited to the same crops and pasture plants, to require similar
management, and to have similar productivity.
● Capability units are generally designated by adding an numeral to the subclass symbol.
● Example : 2e-4 and 3e-6.
Land Suitability
●
Land suitability : suitability as a statement of the adaptability of a given area for a specific kind of land use; others see capability as a
classification of land primarily in relation to degradation hazards (FA), 1976)
●
Land suitability classification is carried out by comparing the criteria for each class with the suitability of land with the characteristics of the land it owns
●
The land suitability classification structure consists of order, classes,
sub-class, units.
Land Suitability
●
Order (Ordo)
S = Suitable (sesuai)
N = non-suitable (tidak sesuai)
Class (Kelas)
S1 = Highly suitable (sangat sesuai)
S2 = Moderately suitable (cukup sesuai)
S3 = Marginally suitable (sesuai marginal)
N1 = Currently not suitable
N2 = Permanently not suitable
Land Suitability
●
Sub-classes : They are designated by adding a small letter :
e : erosion (bahaya erosi)
s : plant roots (kedalaman efektif)
t : topography (lereng)
n : soil fertility (kesuburan tanah)
Units : Capability units are generally designated by adding an numeral to the subclass symbol.
