The long-term application of animal manures and biosolids has resulted in serious environmental issues in many locations. For example, the eastern US has a large amount of farmland characterized as having “excessive P levels” due to heavy application of manures over the last three decades. These soils serve as a significant source for phosphate movement into waters, including the Chesapeake Bay. Elevated phosphate levels in natural waters are a serious concern because it is typically the limiting nutrient for algae and other photosynthetic organisms. Increased phosphate can therefore result in algal blooms and ultimately fish kills and eutrophication. The tendency of phosphorus to move from a soil to surface waters is highly dependent upon its chemical form. In most soils, phosphate has a tendency to form both sparingly soluble phosphate solids and strong sorption complexes with iron and aluminum oxides. These reactions result in phosphate typically being retained by soils. In biosolids and manures, however, high levels of soluble phosphate and readily degradable organic phosphates are found along with more stable organic phosphates and calcium phosphate minerals. Understanding the transformations that occur when biosolids are added to soils is therefore vital information if one is to predict the stability of phosphate in these systems. The speciation is typically performed via sequential chemical extractions, which separate phosphate into different pools based on solubility in progressively stronger chemical extractants. The concern with equential chemical extractions is that they are operationally defined by the researcher and may not truly represent the phases that are present in the soil. To deal with this issue, the presented research will combine synchrotron-based spectroscopy with extractions to monitor the changes in speciation that occur when performing sequential chemical extractions upon soils receiving either inorganic fertilizer or biosolids. At each step of the extraction, a P XANES spectrum of the solid state P speciation is obtained. With this method it is possible to remove the operationally defined limitation of extractions and directly determine the fractions that are removed by the sequential chemical extractions. The end result of such analysis is a better understanding of exactly what extractions are removing and therefore a better guide to choosing extractions better suited for environmental risk analysis.