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PHOSPHORUS FORMS AND CONCENTRATIONS IN SNOWMELT RUNOFF FROM SASKATCHEWAN PASTURES WITH DIFFERENT MANURE MANAGEMENT PRACTICES

The feeding of beef cattle over the winter with bales of dry hay or straw that are spatially dispersed over fields (i.e. bale-grazing) has become common on the Canadian Prairies, replacing confined winter feeding in drylot pens, and has been promoted as a beneficial management practice. In addition to saving producers the cost of spreading manure, it is assumed that the direct deposit of urine and feces will enhance soil fertility. However, this practice also increases the risk of nutrient loss during spring snowmelt runoff while soils are still frozen, which is the main source of runoff on the Prairies. We conducted two experiments in different parts of Saskatchewan, Canada, to study snowmelt runoff after winter bale-grazing. One experiment used small microwatersheds (350 m2), while the other used larger fields (1-2 ha). The experiments ran for 5-7 years, and included controls (summer grazed pasture and fall-spread manure). We used 31P-NMR spectroscopy and chemical analysis to characterize P forms and concentrations in dissolved and particulate edge-of-field snowmelt runoff samples. For both experiments, we observed higher dissolved P in runoff from fall-spread manure but higher particulate P concentrations from bale-grazed pastures. Dissolved P from was predominantly orthophosphate, with only traces of organic P forms. In contrast, particulate was dominated by organic P forms, especially orthophosphate diesters. These results will further our ability to develop appropriate management practices to minimize P loss from agricultural land.

Authors

Cade-Menun, B. J., SCRDC, Agriculture & Agri-Food Canada, Canada, barbara.cade-menun@agr.gc.ca

Hodder, K., Department of Geography, University of Regina, Canada

Iwaasa, A., SCRDC, Agriculture & Agri-Food Canada, Canada

Lardner, H., Western Beef Development Centre, Canada

McConkey, B., SCRDC, Agriculture & Agri-Food Canada, Canada

McMartin, D., Environmental Systems Engineering, University of Regina, Canada

Wilson, H., BRDC, Agriculture & Agri-Food Canada, Canada

Wu, K., Saskatchewan Water Security Agency, Canada

Details

Oral presentation

Session #:003
Date: 02/28/2017
Time: 10:45
Location: 306 A

Presentation is given by student: No