Land use and soil factors affecting accumulation of phosphorus species in temperate soils

• We examined phosphorus species abundance in UK soils.
• P species abundance was related to soil properties.
• We need to consider inorganic and organic P presence and availability.
• Organic P complexation increased for soils with greater C.

Data on the distribution of phosphorus (P) species in soils with differing land uses and properties are essential to understanding environmental P availability and how fertiliser inputs, cropping and grazing affect accumulation of soil inorganic P (Pi) and organic P (Po) forms. We examined thirty-two temperate soils (with soil organic C concentrations 12–449 g C kg− 1 and total P 295–3435 mg P kg− 1) for biogeochemical properties of soil C, reactive surfaces and P by common indices and 31P-NMR spectroscopy on NaOH–EDTA extracts for P species. Arable soil P was dominated by inorganic orthophosphate (276–2520 mg P kg− 1), > monoester P (105–446 mg P kg− 1). The limited diesters, polyphosphates and microbial P in arable soils suggest that cropping and fertiliser inputs limit ecosystem microbial functions and P diversity. Intensive grassland had inorganic orthophosphate concentrations (233–842 mg P kg− 1) similar to monoesters (200–658 mg P kg− 1) > diesters (0–50 mg P kg− 1) and polyphosphates (1–78 mg P kg− 1). As grazing became more extensive P in semi-natural systems was dominated by organic P, including monoesters (37–621 mg P kg− 1) and other diverse forms; principally diester (0–102 mg P kg− 1) and polyphosphates (0–108 mg P kg− 1). These were related to SOC, water extractable organic carbon (WEOC) and microbial P, suggesting strong microbially-mediated processes. A number of abiotic and biotic related processes appeared to control accumulation of different soil P species and gave considerable variability in forms and concentrations within land use groups. The implications are that to increase agricultural P efficiencies mechanisms to utilise both soil Pi and Po are needed and that specific management strategies may be required for site-specific circumstances of soil C and reactive properties such as Fe and Al complexes.