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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #150744
Title: CONNECTING PHOSPHORUS LOSS FROM AGRICULTURAL LANDSCAPES TO SURFACE WATER QUALITY

Author
item MCDOWELL, R - AGRESEARCH LTD
item BIGGS, B - NAT INST OF WATER & ATMOS
item Sharpley, Andrew
item NGUYEN, L - NAT INST OF WATER & ATMOS

Submitted to: Water:Chemistry and Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2003
Publication Date: 12/20/2003
Citation: Mcdowell, R.W., Biggs, B.J., Sharpley, A.N., Nguyen, L. 2003. Connecting phosphorus loss from agricultural landscapes to surface water quality. Chemistry and Ecology. 20:1-40.

Interpretive Summary: Excessive losses of phosphorus from agricultural lands have caused major problems in streams, rivers and lakes through the effects on aquatic ecosystems. These losses might be minor compared with the amount of phosphorus applied as fertilizer or manure; however, aquatic primary producers can be extremely sensitive to even minor increases in phosphorus. Recently, the U.S. Environmental Protection Agency identified eutrophication as the most ubiquitous water quality impairment in the U.S. Agriculture has been identified as a major contributor of phosphorus, a nutrient implicated in accelerated eutrophication of surface waters. Similar problems with eutrophication have been reported in New Zealand, Australia, and Europe. The outcome of human-induced eutrophication is that water use for fisheries and recreation is restricted due to oxygen shortages caused by the decomposition of plant matter and the increased growth of undesirable (and sometimes toxic) algae and aquatic weeds. Better knowledge of the sources of phosphorus in watersheds and how it moves from fields to rivers and streams has enabled the use of more effective control measures. Once phosphorus has left a field, measures can be implemented to retain phosphorus on the landscape. These measures include the use of riparian buffers and natural or constructed wetlands. However, these measures have a finite lifespan and can eventually serve as a source of phosphorus. Despite efforts to retain phosphorus within the landscape, phosphorus will inevitably make it to surface waters. The impact will vary depending on the type of surface water body (small stream to large lake and the variety of aquatic plants present. In some cases, substrate geology may make it impossible to prevent phosphorus concentrations rising to levels high enough to trigger eutrophication. In these cases, remedial measures could focus on strategies to minimize losses at times when algal blooms are most undesirable.

Technical Abstract: Phosphorus is an essential nutrient for productivity in both agricultural and aquatic systems. However, excessive loss of phosphorus from agricultural landscapes is deleterious to the quality of surface water, which may contain undesirable primary producers that are phosphorus limited. When the amounts of phosphorus in runoff are excessive, eutrophication is accelerated by the rapid growth of primary aquatic producers. Even so, the amounts of phosphorus lost and the impact this can have on water quality depend on numerous mechanisms that occur while phosphorus is enroute from fields to water bodies. The aim of this review is to outline these mechanisms and describe how sources of phosphorus in agricultural landscapes are connected to the impairment of surface water quality. We examine the potential for phosphorus loss from the landscape and its subsequent availability to aquatic plants (as the primer for eutrophication), during flow over and through the soil, and into streams, lakes, or reservoirs. In addition to examining the connectivity between phosphorus loss and surface water quality impacts, we also discuss potential mitigation and management of phosphorus losses for various aquatic systems.