Thesis Abstract of AGS Students

Land evluation using ALES model: case study in Phrao district, Chiang Mai province

Pornwilai Saipothong (1995)

Automated land evaluation based on FAO frame work was implemented for agricultural land in Phrao district, Chiang Mai Province. The model was based on Automated Land Evaluation System (ALES) in which decision rules were modified to suit local management practices. Major Land Utilization Types (LUT) in the district for building the models consist of rice, corn, peanut, soybean and peanut-peanut in rainfed area and irrigated rice-soybean.

Land suitability ratings were achieved by matching Land Use Requirement (LUR) of the specific crop, required by each LUT, with Land Quality (LQ) of particular area, defined by the characteristics of soil unit. ALES model was used to construct the decision trees of those LUR, LQ and the suitability classes. The construction of decision trees was straightforward and easily understood for the users. ALES was used to assess both physical and economic suitability. The evaluation results were stored as spatial data that can be further queried, displayed and analyzed through the IDRISI, a raster GIS system.

Results of the current physical suitability assessment indicated that nutrient availability was the main limitation in the study area. Other limitations for growing the crops were flood hazard and steep terrain. Land evaluation for potential uses was conducted by removing those constraints through additional inputs. Kappa statistics was used to compare results of ALES evaluation to those of DLD method and the actual land use in the area. The ALES method results were in agreement with the DLD method for field crop production. The current land use for agriculture in Phrao were found to be located in the suitable classes defined by the ALES method.

The economic suitability evaluation results suggested that 63% and 60% of agricultural area in this study can be used to grow field crops and rice, respectively. About 23% of the area was rated as highly suitable for growing rainfed peanut and 10% of the area was highly suitable for rainfed soybean production.

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