The role of soil microorganisms in enhancing phosphorus availability from dairy processing waste in grasslands

Summary

Dairy processing waste (DPW) is a P rich material that has been suggested as a potential replacement of mineral P fertilizers. In this thesis, I have studied the agronomic value of DPW, in particular the contribution of soil microorganisms and grassland management to improve P cycling in soils amended with DPW. I studied various aspects of this issue, taking into consideration the different chemical forms of P in DPW and soils; the contribution of soil microorganisms; and the implications of grass species selection in P cycling. My results confirm the agronomic potential of DPW as a replacement for conventional mineral P fertilizers. However, my results also show that a transformation of sludge into ash or (hydro)char may result in a decrease in P use efficiency of grasses. I also showed the potential of native soil microorganisms, in particular fungi, and grass species management to improve P use and reduce the demand for P fertilization.