Journal
SOIL RESEARCH
Volume 49, Issue 6, Pages 523-528Publisher
CSIRO PUBLISHING
DOI: 10.1071/SR11151
Keywords
diffuse gradients in thin films; DGT; Colwell P; modelling; phosphorus; rainfall simulation; runoff
Categories
Funding
- Dairy Australia [DAN 12752]
- Grains Research and Development Corporation [UA00103]
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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, r(2) = 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, R-2 = 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.
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