Proceedings - Balai Penelitian Tanah

144
Wahyunto et al.
Soil, climate and other physical environment data (slope, topography,
surface drainage etc) were used to assess a land suitability levels of
various agricultural crop commodities as described in Guidelines for
Land Evaluation (ISRI, 2003). Therefore, Physiographic unit as a
mapping unit is established in order to present the information of soil
characteristic and its environment distribution that have similar
potential development of agriculture crops. This mapping unit is based
on the similarity of terrain, slope, soil surface texture, drainage,
organic layer thickness and tidal, flood inundation and erosion hazard.
Land suitability evaluation for selected economic tree crops and other
agricultural crops were conducted by using Automated Land
Evaluation System (ALES) software package. The crop requirements
were based on “Guidelines for Land Evaluation” by ISRI (2003) and
related references. Adaptation to the guidelines was made as
necessary based on field and laboratory findings. The process of this
evaluation is the matching of crop requirements against land qualities
or characteristics. The law of minimum constrain is applied to
determine the limiting factors of land suitability classes. Selected land
quality in this evaluation includes air temperature regimes, water
availability, rooting condition, nutrient retention, availability of NPK
nutrients, salinity and toxic elements.
In this present study, three suitability classes are recognized in the
Order S Suitability, and a class for order N Not suitable:
Class S1 Highly Suitable: Land having no significant limitations to
sustained application of the given land utilization type, or only minor
limitations that will not significantly reduce productivity or benefits and
will not raise inputs above acceptable level.
Class S2 Moderately Suitable: Land having limitations which in
aggregate are moderately severe for sustained application of the
given land utilization type; the limitations will reduce productivity or
benefits and increase required inputs to the extent that the overall
advantage to be gained from the use, although still attractive, will be
appreciable inferior to that expected on Class S1 land.
Class S3 Marginally Suitable: Land having limitations which in
aggregate are severe for sustained application of the given land
utilization type and will so reduce productivity or benefits, or increase
required inputs, that this expenditure will only be marginally justified.
N Not Suitable order as the range of land utilization types considered
allowed for recommendation of alternatives uses on land whose
present use was found to be Not Suitable
Based on the actual land suitability assessment, it could be grouped
into 4 classes i.e.,: 1 (highly suitable), 2 (moderately suitable), 3
(marginally suitable) and 4 (unsuitable). The main restricting/ limiting
factors can be added to the suitability class are: nr (nutrient retention/
International Workshop on Post Tsunami Soil Management, 1-2 July 2008 in Bogor, Indonesia