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NUTRIENT EXPORT IN RUN-OFF FROM AN IN-FIELD CATTLE OVERWINTERING SITE IN EAST-CENTRAL SASKATCHEWAN

Smith, Amber B.. 2011. University of Saskatchewan

Abstract

Saskatchewan producers traditionally overwinter their cattle in pens in the yard. The practice of winter feeding of cattle directly in the field is increasing in popularity leading to concerns about increased nutrients being deposited in soil and potentially lost in runoff water and to ground water. In 2008/2009 an experiment was conducted to observe the effect of in-field winter feeding of cows on the nutrients in spring snowmelt run-off. Approximately 100 cattle were baled grazed on a Russian wild ryegrass pasture at a stocking rate of 2240 cow-days ha-1 for 88 d during the winter at the Western Beef Development Center at Lanigan, SK. The spring 2009 ponded water was sampled from four basins in the control (no cattle were present) and four basins in the winter feeding treatment from the end of March to mid-April. Ground water samples from two piezometers in the control and two in the winter feeding area were gathered from the start of runoff until the middle of summer. Soil samples (0-10 cm) were collected in the fall 2008 before winter feeding and again in the spring 2009 after winter feeding on both the control and treated areas to examine the influence of winter feeding on soil nutrients. Orthophosphate-P and ammonium-N concentrations were elevated to levels up to 19.9 mg PO4-P L-1 and 102.3 mg NH4-N L-1 respectively in run-off from the winter feed treatment basins compared to the controls (2.1mg PO4-P L-1 and 1.72 mg NH4-N L-1). Nitrate-N concentrations in snowmelt run-off water were similar from the winter-fed areas (0.008 mg NO3-N L-1 to 0.739 mg NO3-N L-1) and the control (0.001 mg NO3-N L -1 to 1.046 mg NO3-N L -1 ). This is explained by lack of sufficient time and temperature for organic N, urea and ammonium in the urine and fecal matter to convert to nitrate. In the ground water there was a slight increase in nutrient ion concentration in the winter feed basins compared to the control. Soil sampled in the spring from the winter feeding site had higher soluble nitrate, ammonium and phosphorus compared to the control. The soluble and exchangeable forms of phosphorus in the soil were lower compared to the fall soil samples for the control and winter feeding site, possibly due to immobilization by plant and microbial uptake in the spring. Caution should be used when selecting sites for in-field winter feeding system so the run-off water does not reach sensitive water bodies.