A mixed qualitative/quantitative physical land evaluation methodology.

Abstract A mixed qualitative/quantitative physical land evaluation methodology is proposed. This mixed approach comprises both qualitative and quantitative methods. The screening of land for serious constraints associated with a defined land utilization type is carried out by qualitative methods based on computer-captured expert knowledge. Subsequently, the more comprehensive quantitative evaluation methods, using computer models to simulate soil-water flow and crop growth, can then be focused on remaining, potentially suited land. The mixed qualitative/quantitative evaluation approach is exemplified with potato-growing in the Netherlands. Decision trees, illustrating how expert knowledge was used to infer potentially suited land from land qualities, are shown. This way, about 65% of Dutch land was found to be potentially suited. This amount turns out to depend on the used soil map. Complex simulation models were used for a quantitative analysis of two potentially suited areas with contrasting soils, namely Calcaric Fluvisols and Humic Podzols. Probability distributions of the land qualities workability and crop water deficit and of the physical suitability expressed as potato tuber yield were determined. The mixed evaluation predominantly uses geographically referenced input data. Therefore, a linkage with geographical information systems (GIS) is a prerequisite for efficient use. After storage in a GIS, some recent projects showed that the mixed approach saved 50%–70% time compared with application of the quantitative evaluation method to all units.