Summer Time Nitrous Oxide Emissions From Long Term Plots Receiving Separated and Whole Dairy Slurry Manure.

Nutrient use assessment must be carried out in long-term trials so that the effects of less available organically-bound nutrients can be assessed in terms of both crop production and possible impact on the environment. In this multi-year trial in a temperate high rainfall climate (coastal British Columbia, Canada), we examined how removing solids from dairy manure slurry affected emissions of nitrous oxide during the growing season.  Solids were removed by settling and decanting which reduced slurry viscosity, enhanced soil infiltration and reduced the organic nitrogen fraction. Over four growing seasons of measurements and with a total nitrogen application of 400 kg/ha/year, separation increased annual emissions of nitrous oxide from about 0.29 to 0.49% of total applied nitrogen, with most of the difference occurring soon after applications. However, at higher total nitrogen applications between 550 and 600 kg/ha/year there was little difference in emissions between the whole and separated manure at 0.54 and 0.55% of applied N, respectively.