Sorption of Inorganic and Total Phosphorus from Dairy and Swine Slurries to Soil
- Sarah K. Marshalla and
- Carrie A. M. Laboski *b
Understanding P sorption from animal manures is essential to formulate best management practices with regard to land application of manure from the standpoint of crop production and environmental quality. Little research has focused on the construction of P sorption isotherms where the P source is manure. The objectives of this study were to: (i) develop a procedure to characterize how inorganic P (Pi) and total P (Pt) from dairy slurry and swine slurry sorbs to soil; and (ii) compare the sorption characteristics of Pi and Pt where the P source was dairy slurry, swine slurry, or potassium phosphate (KH2PO4). Sorption solutions were prepared in 0.1 M KCl at pH 6 and equilibrated with soils at a 1:25 (w/v) soil/solution ratio for 24 h. Inorganic P, Pt, Al, and Fe in the equilibrated solutions were measured. For all soils, Pi and Pt sorption capacity of dairy slurry was greater than KH2PO4 Total P sorption capacity of swine slurry was greater than KH2PO4, while Pi sorption capacity was less than KH2PO4 Overall, Pi and Pt sorption strengths of the manure slurries were less than or equal to KH2PO4 Increased Pi sorption from dairy slurry was correlated with Fe and Al desorption. Reduction of Pi sorption capacity from swine slurry was related to preferential sorption of organic P. Additional studies need to be conducted to determine how differences in P sorption between manures and fertilizer impact in-field P availability to a crop and potential for losses in runoff water.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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