A Comparison of N\u3csub\u3e2\u3c/sub\u3eO Emissions After Application of Dairy Slurry on Perennial Grass or Bare Soil Prior to Planting an Annual Crop in Coastal British Columbia, Canada

Because of restrictions on land application of manure in autumn and winter, dairy farmers in coastal British Columbia (BC) must apply half of their annual manure supply from mid-Feb. to mid-April. Although two thirds of their land is in perennial grass, most of this manure is applied to bare soil, usually maize land, prior to planting. This is done for convenience and to avoid damaging grass stands with equipment traffic. Farmers are encouraged to allocate more manure to grass to minimise soil NO3 concentrations after maize harvest, because maize takes up less N than grass, and the bare fields after harvest are subject to wintertime leaching. However, the effect of this practice on emissions of N2O is not known. Our objective was to compare the effect of spring application of manure on bare land and on grass with respect to emissions of N2O. A second objective was to compare early, late and split applications of manure