Ecosystem restoration is an explicit target in the EU 2020 Biodiversity Strategy since safeguarding ecosystems and preserving their biodiversity is of crucial importance to ensure the long-term preservation of our natural capital. Species-rich semi-natural grasslands have suffered from land-use intensification in recent decades and are hence in need of restoration. A major bottleneck constraining their restoration are the elevated nutrient levels resulting from past fertilization. Residual soil phosphorus (P) is important in this context, because of its persistence in the soil and strong impact on plant communities. Assessing soil P availability is therefore key in determining the restoration trajectory of a certain site. However, current techniques such as field surveys using soil sampling are often labor intensive, expensive and provide low spatial coverage. This project aims to move towards a more cost-efficient approach using vegetation spectra to map soil P-levels. The development of such an approach includes (1) resolving the plant ecological basis underlying the linkages between soil P, the vegetation chemical and spectral signature, (2) deriving spectral proxies for vegetation P and (3) optimizing and evaluating the cost-effectiveness of a field survey approach. These results will be translated into concrete guidelines to aid end-users in determining how to assess soil P-levels in the most cost-effective way.