. 2003. Interactive effects of composts and liquid pig manure with added nitrate on soil carbon dioxide and nitrous oxide emissions from soil under aerobic and anaerobic conditions. Can. J. Soil Sci. 83: 343-352. The composting process results in immobilization of inorganic N. When high-Ndemanding crops are grown in compost-amended soils, additional N fertilizer is often applied. The combination of elevated nitrate levels from N fertilizer and high C inputs from the compost may result in enhanced greenhouse gas emissions. Hence, the objective of this laboratory incubation study was to characterize CO 2 and N 2 O emissions from a Brookston clay loam soil that has received organic amendments in the presence or absence of added nitrate. The organic amendments included urban yard waste compost (YWC), liquid pig manure + wheat straw compost (PMC), and liquid pig manure (LPM). The nitrate treatments included added nitrate (100 mg KNO 3 -N kg soil -1 ) or no added nitrate. Total CO 2 emissions during aerobic incubation followed the pattern: YWC > LPM > PMC > control (no organic amendments) for both nitrate treatments. Nitrate addition increased CO 2 emissions from the YWC-and LPM-amended soils by 9 and 43%, respectively, but had no significant effect (P < 0.05) on CO 2 emissions from the control or the PMC-amended soil. All organic amendments increased N 2 O emissions compared to the control. When nitrate was added to aerobically incubated LPM-amended soils, N 2 O emissions were increased over seven times; however, N 2 O emissions were decreased by 93% for PMC-amended soils and by 50% for YWC-amended soils. These decreases in N 2 O production occurred when nitrate was added to the YWC and PMC treatments under aerobic conditions but not under anaerobic conditions. Composted liquid pig manure was found to be more environmentally friendly than raw liquid pig manure as it stabilized the manure C and reduced CO 2 and N 2 O emissions compared to the liquid pig manure. . Pour le nitrate, le traitement consistait en l'addition ou pas de nitrate (100 mg de KNO 3 -N par kg de sol). Les dégagements totaux de CO 2 durant l'incubation aérobique suivent la progression YWC > LPM > PMC > témoin (aucun amendement organique) pour les deux traitements au nitrate. L'addition de nitrate augmente les émissions de CO 2 des sols bonifiés avec du YWC et du LPM de 9 % et de 43 % respectivement, sans incidence significative (P < 0,05) sur les émissions de ce gaz par le sol témoin et celui amendé avec du PMC. Tous les amendements organiques augmentent les dégagements de N 2 O comparativement au sol témoin. Quand on ajoute du nitrate au sol amendé avec du LPM, l'incubation aérobique multiplie les émissions de N 2 O par sept, mais ces dernières baissent de 93 % pour le sol bonifié avec du PMC et de 50 % pour celui amendé avec du YMC. Ces baisses surviennent quand le nitrate est ajouté à ces deux derniers types de sol dans des conditions aérobiques mais non anaérobiques. Le compost de lisier est moins dommageable pour l'environnement que le lisier b...