Eva Brod, Anne Falk Øgaard, Eddy Hansen, David Wragg, Trond Knapp Haraldsen og Tore Krogstad
This work was supported by the research projects CenBio (Bioenergy Innovation Centre, Grant No. 193817) and Innovative utilization of wood ash (Grant No. 215935). Both are co-funded by the Research Council of Norway and research and industry partners.
We then used the characterisation data to explain the results of a bioassay studying the fertilisation effects of waste and manure products after application to a nutrient-deficient model soil that was limed to two pH levels (approximately pH 5.5 and 6.9 at pH level 1 and 2), with ryegrass (Lolium multiflorum) as the experimental crop. The P in waste products was mainly present as a complex mixture of inorganic P species, predominantly Ca phosphates with differing solubility. Fertilisation effects were largely explained by sequential fractionation data, with a positive relationship between apparent P use efficiency and the H2O-soluble inorganic P fraction at pH level 1 (R2 = 0.52) and a negative relationship between apparent P use efficiency and the HCl-soluble inorganic P fraction at pH level 2 (R2 = 0.66). X-ray powder diffraction and solid-state 31P MAS-NMR spectroscopy confirmed the sequential fractionation data, but provided little additional information.