Variation in environmentally- and agronomically-significant soil phosphorus concentrations with time since stopping the application of phosphorus fertilisers

Following the cessation of P fertiliser to a P enriched pasture soil, indicators of potential P loss (WEP and CaCl2-P) decreased exponentially with time. Soil P fractionation revealed a similar pattern occurred in bioavailable inorganic P fractions (principally NH4Cl, HCO3 and NaOH extractable pools). However, the addition of 50 kg N ha−1year−1 to one treatment was not great enough to speed up the rate of decline in P fractions or P loss indicators compared to the same treatment without N applied. 31P NMR data indicates that while the frequency of detecting