Phosphorus is characteristically one of the three important plant nutrients found in soils. Identifying P quantities originally contained in Central Great Plains soils will help shed some incite on historical farming practices in this region. We sampled soils that ranged from the shortgrass steppe in Colorado, through the mixed-grass prairie, and to the tallgrass prairie in eastern Kansas. The soils were obtained from 5 Long-Term Ecological Research (LTER) sites - areas that had not been used for agricultural practices. We used a sequential extraction procedure to identify the following P fractions: soluble, Al-bound, Fe-bound, occluded, and Ca-bound. Our results showed soluble P to be at or below detection limits at all site, illustrating the high turnover rate of soluble P in these undisturbed systems. The Al-bound fraction was variable across sites. The Fe-bound P contributed to the total P fraction only from the mixed grass prairie eastward. The occluded P fraction was greater in the shortgrass steppe, decreased dramatically as we moved slightly eastward, then increased significantly in the tallgrass prairie. The Ca-bound P fraction showed results opposite of the occluded fraction. The historical boundary between the corn and wheat belt showed greater P in the occluded fraction associated with the corn belt, and greater P in the Ca-bound fraction associated with the wheat belt. Implications will be discussed.
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