Estimating soil aggregate stability with infrared spectroscopy and pedotransfer functions

Soil aggregate stability is an important indicator of soil condition and is directly related to soil degradation processes such as erosion and crusting. Aggregate stability is conventionally measured by testing the aggregate resistance to water disturbance mechanisms. Such measurements, however, are costly and time-consuming, which make them difficult to implement at a regional or country scale. In this study, we explore two different approaches to estimate soil aggregate stability by means of commonly-measured soil properties or mid-infrared spectroscopy measurements. The first approach relies on land use and soil properties. In the second approach aggregate stability is estimated by a model fitted with mid-infrared spectroscopic data. We tested the two approaches with a dataset composed of 202 soil samples from mainland France, in which aggregate stability was measured with a fast wetting test. We found that simple linear models based on common soil properties and models based on mid-infrared spectral data yielded similar results. Interpretation of the models revealed well-known relationships: land use had a major role in predicting aggregate stability, followed by organic carbon and clay content. Overall, we conclude that both approaches offer a reliable, cheap and time-efficient alternative to estimating soil aggregate stability. These approaches offer a tool to estimate aggregate stability over large geographical areas, which can support the development of erosive risk management plans and the implementation of adaptive management strategies to mitigate threats to soil and improve the overall soil condition.