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Phosphorus Availability and its Relationship to Sorption Maximum and Sorption Strength

Start Date: 2013
Principal Investigator: Paulo Pagliari
Organization: University of Minnesota
Status: Complete

Background Info

Understanding soil phosphorus (P) and what soil properties affect P availability in soil is crucial to improving P management in land used for agriculture. Over the last century soil P has been the focus of innumerous scientific articles, which has helped in the development of current strategies for P management. Currently, two different mechanisms are used to study soil P, one focus on soil P buffer capacity (PBC) and the other focus on the parameters sorption maximum and sorption strength. Both mechanisms are extremely important in developing a good understanding of P dynamics in soils. However, there is no research in the literature that has provided a link between the two mechanisms. In addition, there is no research that has reported what soil property/properties controls soil PBC and the sorption maximum and sorption strength. Although some researchers have hypothesis, there are no concrete evidences that prove or disprove any of those hypothesis. Therefore, the objective of this research was to try and relate the soil PBC to sorption maximum and sorption strength and also determine which soil property/properties controls these parameters.


Determine the soil adsorption coefficients sorption maximum (b) and sorption strength (k) in the soils collected for the study.

Key Findings

PBC values estimated using the Bray-1 test ranged between 1.2 and 2.9 and the PBC values with the other extractants (Olson, water and Mehlich-3) were similar.

By adding enough P to saturate the binding sites we observed a completely new P behavior in the soil that questions the meaning of adsorption studies and what the sorption strength and maximum really mean.

The higher the PBC value the higher the amount of P that has to be added to a soil to increase the available pool by 1 ppm.

New results indicate that there is no real limit in how much P can really bind to a given soil.

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