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Phosphorus Availability and its Relationship to Sorption Maximum and Sorption Strength

Study author(s): Paulo Pagliari, Organization: University of Minnesota 
Years of study: 2015
Location(s): Minnesota, Texas, Wisconsin

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 increase in soil test P (STP) for the Zimmerman soil as determined by the Bray-1. The linear response in the increase in STP as a function of P application rate observed for the Zimmerman soil was similar to the increase in STP observed for all other soils using the Bray-1 test.

Table 1 shows the PBC values for all soils as determined by the Bray-1, Olsen, Water, and Mehlich-3 extractants. PBC values estimated using the Bray-1 test ranged between 1.2 and 2.9; the Olsen it ranged between 2.1 and 8.1; Mehlich-3 ranged between 1.2 and 11.6; and for the water it ranged between 1.8 and 9.7 (Table 1). Within each extractant, the mean value and median we very close between all soils. For the mean and median values for the Bray-1 extractant was 2.1 and 2.0; for the Olsen they were 4.2 and 4.0; for the Mehlich-3 they were 2.3 and 2.0; and for the Water they were 3.9 and 3.7, respectively.

The values for the PBC observed in this study are coherent with other studies published in the literature. However, the most important findings in this research is the fact that the increase in soil test P was linear for all rates applied, no matter how high there were.

The next phase of the study will help us make the correlations needed to provide a complete understanding of the soil properties that control the behavior of P in soils.

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