( availability and increased rainfall resulting in reduced aeration. Split N application was effective in reducing N 2 O emissions by minimizing the supply of NO 3 ( when demand for terminal electron acceptors was high. N 2 O emissions were higher in the potato hill relative to the furrow; however, denitrification rate was higher in the furrow. Nitrate intensity (NI) expresses the exposure of the soil microbial population to NO 3 ( and was calculated as the summation of daily soil nitrate concentration over the monitoring period. Cumulative N 2 O emissions were positively related to NI across year, N fertility treatment and row location. Denitrification was not related to NI, reflecting the primary role of NO 3 ( in influencing the N 2 O:N 2 ratio of denitrification rather than the magnitude of the overall process. Split N application was an effective strategy for reducing N 2 O emissions in years where there was significant rainfall during the period between planting and hilling. ( dans le sol combine´e a`des pre´cipitations plus abondantes, facteurs qui ont nui a`l'ae´ration du sol. L'application fractionne´e d'engrais N re´duit les de´gagements de N 2 O en abaissant la quantite´de NO 3 ( quand la demande d'accepteurs d'e´lectrons finaux est e´leve´e. Les e´missions de N 2 O sont plus importantes sur la butte que dans le sillon; cependant, c'est dans le sillon que la de´nitrification est la plus intense. La charge nitrique (CN) indique le degre´d'exposition de la microflore tellurique aux NO 3 ( et correspond a`la somme de la concentration quotidienne de nitrates dans le sol durant la pe´riode a`l'e´tude. Les e´missions cumulatives de N 2 O sont positivement corre´le´es a`la CN pendant l'anne´e, a`la fertilisation azote´e et a`l'emplacement du rang. La de´nitrification ne pre´sente aucun lien avec la CN, signe que le NO 3 ( joue un roˆle primordial en modifiant le ratio N 2 O:N 2 de la de´nitrification et non l'amplitude du phe´nome`ne. L'application fractionne´e d'engrais N est une bonne strate´gie pour re´duire les e´missions de N 2 O les anne´es ou`il pleut beaucoup durant la pe´riode qui se´pare la plantation du buttage. For personal use only.

. 2008. Nitrous oxide emissions from denitrification and the partitioning of gaseous losses as affected by nitrate and carbon addition and soil aeration. Can. J. Soil Sci. 88: 133Á143. National inventories of N 2 O emissions from agricultural situations are being developed; however, the factors controlling such emissions may vary with soil and environmental conditions and management practices. This study determined the relative importance of soil aeration, as measured by water-filled pore space (WFPS), NO , N 2 O emissions and denitrification were low and were increased by both NO ( 3 and C addition treatments. Carbon source was investigated by amendment with glucose, red clover or barley straw. Based on the quantity of soil respiration per unit of C added in the amendment, C in the red clover and barley straw was estimated to be 48 and 28% as available as glucose C. When corrected for C availability, cumulative N 2 O emissions averaged 0.010, 0.011 and 0.002 mg N kg(1 soil, and cumulative denitrification averaged 0.014, 0.014 and 0.003 mg N kg (1 soil, for each 1.0 mg C kg (1 soil of available C added as glucose, red clover or barley straw, respectively. NO ( 3 addition had no effect on denitrification, but increased N 2 O emissions, especially where C availability was high. The amount of denitrification was controlled primarily by soil O 2 supply, as controlled by WFPS and C availability. The N 2 O:(N 2 O'N 2 ) ratio was generally high in cases where the supply of O 2 or NO 3 Á was sufficient to meet the demand for terminal electron acceptors. For personal use only.