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

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Date
2015-11-01
Type
Journal Article
Fields of Research
Abstract
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.
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