Agro-Ecological Zoning for South West Selangor
using Remote Sensing and Geographic Information System
4.0 Materials and Methods
The agro-ecological assessment of land and climate for agricultural suitability resided on three compound activities, namely, (I) Inventory of land utilization types (LUTs) and their requirements, (ii) Inventory of land resources and determination of agro-ecological zone (AEZ) based on bio-physical parameters and (iii)Evaluation of LUTs suitability for each AEZ for production of the agro-land suitability zone.
Inventory of LUTs
The LUTs relevant for the state of Selangor are (I) Industrial crops - oil palm, rubber and cocoa and (ii) Food crop - Paddy. The requirements for optimum growth of these crops were taken from the FAO guideline entitled 'Agro-ecological Zoning' with modifications to suit Malaysian conditions.
Land Resource Inventory
This comprised land/use cover, soil, landform and climate characterization of the area. Landsat TM data were used to extract these information, substantiated by intensive ground thruthing and ancillary data -geology, topography and land/use cover maps. The terrain layer was generated from a digital elevation model (DEM) derived from digitized contour lines.
Soil formation in Malaysia is greatly influenced by relief, landform ad geological sub-stratum. Therefore, in the visual analysis of the satellite data (Landsat TM 453) for soil information extraction, the digitized geology and landform vector layers were superimposed on the satellite image to help delineate more reliable soil boundaries. Field inspections were also conducted to verify the soil mapping units determined.
Detailed land/use/cover information were extracted from the satellite data (Landsat TM 453) through visual interpretation with the aid of existing land use data, derived from aerial photographs. Land use/cover units which were inseparable visually, were classified as mixed classes (example oil palm -rubber).
In the climate characterization of the study area, two parameters were considered-duration of dry season (period where the Agricultural Rainfall Index <40% with >20% probability) and the Average Annual Precipitation Distribution. These climate data were computed from 16 rainfall stations within and around the study area and ingested from the GIS as point files. The corresponding raster layers were output in the GIS through interpolation techniques.
Delineation of agro-ecological zones
Delineation of the agro-ecological zones of the study area was done in a GIS environment using overlay analysis in the spatial domain. Its basically a bio-physical assessment of land and climatic parameters, resulting in zones of similar soil, climate, terrain and landform characterizations.
Agro-land Suitability Zones
Under the FAO guidelines four classes of agro-land suitability can be evaluated for -very suitable, suitable, marginal and unsuitable. Matching the requirements of paddy, oil palm, rubber and cocoa with the land-climate characteristics of each AEZ through cross tabulation in the GIS has enabled the production of the agro -land suitability map. The present land use was also given due consideration in this assessment.
