Abstract
In this study, we conduct a spatial analysis of soil total phosphorus (TP), acid extractable phosphate (PO(4)) and the stable oxygen (O) isotope ratio within the PO(4) molecule (δ(18)O(PO(4)) ) from an intensively managed agricultural grassland site. Total P in the soil was found to range from 736 to 1952 mg P kg(- 1), of which between 12 and 48% was extractable using a 1 M HCl (HCl(PO(4)) ) solution with the two variables exhibiting a strong positive correlation. The δ(18)O(PO(4)) of the extracted PO(4) ranged from 17.0 to 21.6‰ with a mean of 18.8‰ (± 0.8). While the spatial variability of Total P has been researched at various scales, this is the first study to assess the variability of soil δ(18)O(PO(4)) at a field-scale resolution. We investigate whether or not δ(18)O(PO(4)) variability has any significant relationship with: (i) itself with respect to spatial autocorrelation effects; and (ii) HCl(PO(4)) , elevation and slope - both globally and locally. Results indicate that δ(18)O(PO(4)) was not spatially autocorrelated; and that δ(18)O(PO(4)) was only weakly related to HCl(PO(4)) , elevation and slope, when considering the study field as a whole. Interestingly, the latter relationships appear to vary in strength locally. In particular, the δ(18)O(PO(4)) to HCl(PO(4)) relationship may depend on the underlying soil class and/or on different field managements that had operated across an historical north-south field division of the study field, a division that had been removed four years prior to this study.