Soil organic carbon models need independent time-series validation for reliable prediction

For those models aiming at prediction, validation is a critical step to gain confidence in projections. With a comprehensive review of similar to 250 models, we assess how models are validated depending on their objectives and features, discuss how validation of predictive models can be improved.

We find a critical lack of independent validation using observed time series. Conducting such validations should be a priority to improve the model reliability. Approximately 60% of the models we analysed are not designed for predictions, but rather for conceptual understanding of soil processes.