Quantified evaluation of agricultural soil capability at the local scale: a GIS‐assisted case study from Ontario, Canada

Abstract

Abstract. Rural agricultural areas in southern Ontario, Canada, with potential for aggregate extraction have become a focus of conflict over proposed land use change. Geophysical and soil physical field measurements were used to map soil variation for quantitative land evaluation at the farm level. Apparent electrical conductivity of terrain was shown to be strongly correlated with depth to the groundwater table on two separate test sites. A digital terrain model was used to create thematic maps of the predicted pre‐growing season soil water regime by contouring irregularly spaced electromagnetic survey and soil inspection points. Overlay analysis with a geographical information system (GIS) was used to produce an agricultural soil capability map for crop production. Adoption of a larger map scale provided significant refinement in detail over the published Canada Land Inventory soil capability ratings for agriculture, but both showed that Class 2 soils are dominant. The approach can improve the reproducibility of land capability assessments.

How good is a reconnaissance soil map for agronomic purposes?

“…There are many situations, where soil maps or soil classifications are useful in agronomic decision-making processes, such as land use planning or the adjustment of fertilizer rates according to soil types in a region. Soil maps are also used in many land evaluation and crop growth simulation studies (Wolf et al, 1989;Chinene, 1992;McBride & Bober, 1993), but quantitative error assessment in such GIs-supported modelling activities requires estimates of the within-map unit variance (Burrough, 1992).…”