Linkages between phosphorus index estimates and environmental quality indicators

A growing concern over water quality in agricultural areas highlights phosphorus (P) as a key constituent in eutrophication and degrading water quality. A preliminary analysis is presented that tests the effectiveness of P index predictions using linkages to sediment and surface water P concentrations. The field P status in the Elk Creek watershed is described according to P inputs by land managers, soil characteristics, and sediment and water quality analyses. The watershed is partitioned into contributing areas, and the available P in soils shows an increase in concentration in the downstream direction. The P index ratings also show an increase in vulnerability for P loss from soil to surface waters in the lower part of the watershed. The rankings are in agreement with the intensity of land use, and this is reflected in the increase in predominance of the source factors as the main contributor to the P index ratings. In spite of complex process interaction associated with sediment movement, the stream sediment showed similar trends to the soils and P index ratings. Increases in total P in wetseason stream water at the outlet of the watershed may indicate the downstream cumulative effects predicted by the P index ratings.