Modern phosphorus (P) fertiliser production depends on phosphate rock reserves which could be exhausted by 2040. Substituting inorganic P with organic fertilisers may reduce farmers’ requirements for rock-derived phosphate while encouraging the use of waste products. Research shows that integrating the use of organic and inorganic fertilisers increases P phytoavailability compared to the application of inorganic P alone. Field studies typically report results of one sampling occasion conducted after years of experimentation, with no intermittent monitoring. The aim of this thesis was therefore to determine how substitution of inorganic P with organic alternatives affects short-term P cycling and wheat productivity. Results were obtained from intact soils cores maintained in a greenhouse sown with winter wheat and fertilised with different ratios of organic-to-inorganic P. There was no statistically significant effect of substituting inorganic P with pig slurry (PS) or digested cake (DC) on available P concentration during stem elongation or anthesis compared to the application of inorganic P alone. The results suggest that increases in phytoavailable P reported in previous studies following integrated fertiliser management (IFM) may not develop immediately but through gradual accumulation of the soil reserve. The time it takes for these differences to emerge could depend on the organic amendment; repeated measures analysis showed that the PS substitution treatment provided a more sustained supply of phytoavailable P than the DC substitution treatments. Grain yield and P leaching losses were statistically similar between treatments. The thesis therefore shows that in the short term, inorganic P use could be reduced through the incorporation of organic amendments to soil without compromising yield, P phytoavailability or P leaching losses. P application rates should be matched between treatments and respond to changes in P phytoavailability between seasons to better understand the effect of IFM on P cycling and yield over time
