The Nature of Phosphorus Behavior in Soils
Study author(s): Paulo Pagliari, University of Minnesota, Southwest Research and Outreach Center
Years active: 2016
Important: for the complete report, including all tables and figures, please download using the links to the right.
Figure 1 shows the response observed in the P adsorption as a function of P concentration in the solution. The results of this study show two distinct behavior. One behavior is well known and is the behavior we were attempting to better understand and is the behavior that takes place from 0 to about 100 mg P L-1. For P concentration above the 100 mg P L-1, a second unexpected behavior takes place. We are not yet sure why this second behavior is happening but it has never been reported in the literature before. It appears that there is a change in phase controlling P adsorption in soils when the P concentration reaches a limit value. Further studies will be needed to fully understand this behavior.
The results observed for the first behavior, however, are well within the expected range and also is very similar to the results reported in the literature for soils with similar properties (Laboski and Lamb, 2004). Table 1 has the adsorption coefficients for selected soils and were developed for P concentrations up to 100 mg P L-1. Coefficients for the full range in P concentration will only be possible after new mathematical equations are developed.
In the next phase of the study we will start to combine the results observed in the first study, the one where we develop PBC curves, with the results from this study. The correlations will help us make to provide a complete understanding of the soil properties that control the behavior of P in soils.