The recent reduction in phosphorus fertilisation can affect plant production negatively on a large part of Swedish arable land, because low P levels in the soil can cause lowered N-efficiency. The goal of this project is to contribute to improved recommendations on optimal doses of phosphorus (and nitrogen), that simultaneously limit leaching and emissions.
Furthermore, new observations also suggest that the utilisation of phosphorus in organic fertilisers is significantly lower compared to mineral fertilisers, both in the short and long term, which contradict previous belief that the long-term effect is similar for different phosphorus fertilisers. This should also be investigated in this project.
The Swedish long-term soil fertility experiments offer good opportunities to determine optimum levels, because different levels of both N and P are applied separately. These experiments also have systems with and without manure, so that the significance of this supply can be determined.