Saturday, 15 July 2006

Redox Effects on Phosphorus Release Following Soil Deposition in a Riparian Wetland.

W. Dean Hively1, Rebecca Blank2, Greg McCarty1, Martin Rabenhorst2, Randy Rowland1, and Omotomike Ogunwumiju1. (1) USDA-ARS Hydrology and Remote Sensing Loboratory, Building 007, Room 007, BARC-W, 10300 Baltimore Avenue, Beltsville, MD 20705, (2) Univ of Maryland, 0206 HJ Patterson Hall, College Park, MD 20742

A field experiment was conducted at the USDA-ARS Agricultural Research Center at Beltsville, Maryland USA in the fall of 2005, with the objective of determining the fate of phosphorus bound to sediment eroded from the upland landscape and deposited in a riparian wetland. Five sampling locations were established: one in a moderately well drained mineral soil at the upland edge of the riparian zone (control site), and four in hydric, organic-rich alluvial soils within the riparian wetland. At each location the soil redox potential (Eh) was continuously monitored using replicate platinum electrodes installed at three depths (10, 25, and 40 cm). Additionally, an integrated measure of redox effect was provided by 50-cm iron oxide coated PVC pipes (IRIS tubes) that were evaluated for percent removal of the ferric iron coating following two weeks in the soil. Packets of homogenized upland agricultural soil were buried (10 cm) at each site for two-week intervals, with anion exchange membranes (AEM) placed in contact with the buried soils to monitor the release of orthophosphate. Additional sampling included soil temperature and pH, leaf fall, water table, and groundwater phosphorus. We hypothesize that autumn leaf fall will lead to a temporary increase in available soil carbon that will promote soil reducing conditions in the saturated areas, thereby increasing phosphorus release from the buried upland soils.

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