DIVISION S-8 - NUTRIENT MANAGEMENT AND SOIL AND PLANT ANALYSIS - NITROUS-OXIDE EMISSIONS FROM AGRICULTURAL SOILS OF THE BOREAL AND PARKLANDREGIONS OF ALBERTA

The contribution of agricultural soils to atmospheric N2O in the Borea l and Parkland regions of Alberta is largely unknown. Field data are r equired to quantify the flux of N2O from these regions, as are methodo logies to scale up from site-specific measurements to large geographic al areas. Climate-soil-management combinations (CSMCs) aggregated to a n ecodistrict le,el have recently been proposed as a technique for sca ling up greenhouse gas flux estimates for Canadian agriculture, Our ob jective was to calculate seasonal N2O losses and investigate large-sca le spatial variability using field data from selected sites in the Bor eal and Parkland regions. We used vented soil covers to measure N2O em issions during spring and summer of 1993 and 1994, and the spring of 1 995, from six representative CSMCs in five ecodistricts in Alberta, Su bstantial and consistent differences in the magnitude of N2O-N loss am ong sites were observed, with annual estimated losses of N2O-N ranging from 0.4 to 2.6 kg ha(-1) Up to 70% of the total annual N2O-N loss oc curred during brief but intense bursts at spring thaw. Soil clay conte nt was found to be strongly correlated with annual N2O-N loss. This re lationship suggests that clay content, readily available from soil dat a bases, could be used as a N2O-loss predictor variable when applying scaling-up methodologies.