Baseline values and change in the soil, and implications for monitoring

The soil is subject to change, and this must be monitored and understood. There are various circumstances in which the change in a soil property will depend in part on the baseline value that was first measured. Such a relationship may allow us to estimate change with greater precision, but it will also reflect in part the statistical phenomenon of regression to the mean. In this paper, we describe two approaches to the analysis of how change in a variable depends on its baseline values. These methods allow for the effect of regression to the mean. We discuss their applicability to the problems of soil monitoring, and we illustrate one of them by means of a case study on change in the organic carbon content of the soils of England and Wales.