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There is a need to be able to identify soils with the potential to generate high concentrations of phosphorus (P) in runoff, and a need to predict these concentrations for modelling and risk-assessment purposes. Attempts to use agronomic soil tests such as Colwell P for such purposes have met with limited success. In this research, we examined the relationships between a novel soil P test (diffuse gradients in thin films, DGT), Colwell P, P buffering index PBI), and runoff P concentrations. Soils were collected from six sites with a diverse range of soil P buffering properties, incubated for 9 months with a wide range of P additions, and then subjected to rainfall simulation in repacked trays growing pasture. For all soil and P treatment combinations, the relationship between DGT (0–10 mm) and runoff P was highly significant (P < 0.001, r2 = 0.84). Although there were significant curvilinear relationships between Colwell P and runoff P for individual soils, there were large differences in these relationships between soils. However, the inclusion of a P buffering measure (PBI) as an explanatory variable resulted in a highly significant model (P < 0.001, R2 = 0.82) that explained between-soil variability. We conclude that either DGT, or Colwell P and PBI, can be used to provide a relative measure of runoff P concentration.

Item Type:	Refereed Article
Research Division:	Environmental Sciences
Research Group:	Soil Sciences
Research Field:	Soil Chemistry (excl. Carbon Sequestration Science)
Objective Division:	Environment
Objective Group:	Land and Water Management
Objective Field:	Sparseland, Permanent Grassland and Arid Zone Land and Water Management
Author:	Burkitt, LL (Dr Lucy Burkitt)
ID Code:	72914
Year Published:	2011
Web of Science® Times Cited:	12
Deposited By:	Agricultural Science
Deposited On:	2011-09-04
Last Modified:	2014-12-01
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