Soil quality monitoring in New Zealand: development of an interpretative framework

Schemes to monitor soil quality must be associated with quality criteria that allow for an objective assessment of what the measured values signify in relation to soil quality. The derivation of an interpretative framework for a broad-scale New Zealand monitoring scheme is described. The basis for the framework is a set of interpreted response curves that were developed by soil quality experts in a workshop process. The curves combine both production and environmental goals, and are specific to particular combinations of land use and soil type. Appropriate target ranges for each soil indicator are derived from these curves. Techniques for aggregating and presenting the results of a comparison of sampled data with the target ranges are discussed. There are advantages in assessing quality by both individual soil property, and by grouping properties into one or more indices. This interpretative framework (target ranges and aggregating techniques) can be applied to the assessment of a single sample, or to summarize the overall quality in a region or country. We anticipate that the target ranges will become better defined as more data become available; at present they are better suited for assessing soil quality at a broad regional scale than for specific on-farm assessment.