A comparison of qualitative and quantitative physical land evaluations, using an assessment of the potential for sugar‐beet growth in the European Community

Abstract

Abstract. Qualitative and quantitative physical land evaluations differ in their technical procedures, i.e. use of expert knowledge versus process‐orientated simulation models. This paper compares the results of both procedures using the growth potential for sugar‐beet in the European Community. Qualitative procedures give suitability expressions, such as land being well suited or moderately suited for a given land use. Less than 30% of EC land was found to be well suited or moderately suited under water‐limited conditions. No quantitative expressions for the crop yield potential are, however, produced. The quantitative procedure describes suitability in terms of average crop yield and its temporal variability. Water‐limited and potential dry matter yields of sugar‐beet were estimated to range from 3.5 to 20 t/ha, and from 6 to 25 t/ha, respectively.Comparison of results of the qualitative and quantitative procedures for regions showed that the suitability classes obtained by the former can be characterized by different yield distributions derived from the latter. These yield assessments showed that results of qualitative land evaluation procedures aimed at assessing yield potential are meaningful only when they are linked to agroclimatic zones. The comparison also showed that some moderate restrictions, which often can be counteracted by adequate farm management, are not incorporated into the quantitative procedure.