Long-term phosphate fertilization trials

This project aims to obtain a better understanding of phosphate binding and release in agricultural soils. To this end, an extensive dataset of two long-term phosphate fertilization field experiments on a sandy non-calcareous and a loamy calcareous soil will be explored. With this dataset, I will analyse the development of soil phosphorus (P) test (SPT) results as a function of a variable P dosage over time, and how these measurements are related to crop yield. In one of the two field experiments, different mineral P fertilizer types have been used, the effect of which will also be analysed in my study. Additionally, dedicated P speciation measurements using spectroscopic techniques will be performed to further the understanding of how the results of the SPTs have developed over time. Furthermore, I will explore how the relationships between various SPTs vary between the two soil types and which soil characteristics are responsible for this variation. Finally, mechanistic modelling will be used to identify the soil chemical processes that control P solubility and how this solubility is affected by relevant soil characteristics.