Step 5 Evaluate Land Suitability

For each of the promising land uses identified in step 4, the land requirements have to be established and matched with the properties of the land in the planning area to establish physical land suitability. To do this, the land-use types should be described in terms of their products and management practices. Depending on the geopolitical level, the descriptions should be more or less detailed; that is, at district and local levels, more detail is necessary than at national levels.

Next, the land-use requirements are described by the land qualities (e.g., availability of water and nutrients) necessary for sustained optimal production. Most land qualities are determined by the interaction of several land characteristics, that is, measurable attributes of the land.

The land units identified in step 3 should be mapped in more detail when necessary. Land units are choosen because they are expected to respond to management in a relatively similar ways at similar scales of study. The need to carry out original surveys depends on the need for and availability of these data.

Now, the requirements of the land-use types can be compared to the properties of the land units. Each land unit can be put into a land suitability class for each land-use type. Table 2.2 gives the structure of the standard land suitability classification used by the FAO. The limiting values of land quality or a land characteristic determine the class limits of land suitability for a certain land use. First, a determination has to be made as to whether the land unit is suitable or not suitable. The important criteria used in this decision are sustainability and ratio of benefits and costs.

After the land suitability classes of the different land units are determined, the matching of land use with the land quality starts. Compare the requirements of each land-use

Table 2.2. Structure of FAO land suitability classification

Code

Classification

Description

S

SUITABLE

The land can support the land use indefinitely and benefits justify inputs.

S1

Highly suitable

Land without significant limitations. Include the best 20%—30% of suitable land as S1. This land is not perfect but is the best that can be hoped for.

S2

Moderately suitable

Land that is clearly suitable but that has limitations that either reduce productivity or increase the inputs needed to sustain productivity compared with those needed on S1 land.

S2ea

Land assessed as S2 on account of limitation of erosion hazard.

S2w

Land assessed as S2 on account of inadequate availability of water.

S3

Marginally suitable

Land with limitations so severe that benefits are reduced and/or

the inputs needed to sustain production are increased so that this cost is only marginally justified.

N

NOT SUITABLE

Land that cannot support the land use on a sustained basis, or land on which benefits do not justify necessary inputs.

N1

Currently not suitable

Land with limitations to sustained use that cannot be overcome at a currently acceptable cost.

N2

Permanently not suitable

Land with limitations to sustained use that cannot be overcome.

N2ea

Land assessed as N2 on account of limitation of erosion hazard.

a There is no standard system for letter designations of limitations; first-letter reminders should be used where possible. Source: [6].

type with the qualities of each land unit. Check measured values of quality or characteristics against the class limits and allocate each land unit to its land suitability class according to the severest limitation. Consider which modifications to the land-use type will be most suitable. Also, consider which land improvements could make the land better suited for the type of land use. Land can be made physically suitable for many types of land use. Sometimes, however, these technical changes are so intense that the land is no longer sustainable or the change is not economically feasible. In those cases, the proposed land use is not possible on that specific piece of land. One also can argue about which interferences are still contributing to a sustainable environment and which are not.

The last part of this step concerns the mapping of the land suitability, which shows the suitability of each land unit for each land-use type.

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