The impacts of compost type on corn grain yields over 10 yr and N 2O and CO 2 emissions in the first 3 yr after compost application were evaluated on a Brookston clay loam soil in Woodslee, ON. The treatments included yard waste compost (YWC), kitchen food waste compost (FWC), and pig manure compost (PMC), which were applied once in the fall of 1998 to field plots at a rate of 75 Mg ha -1 (dry weight basis) and no further applications occurred thereafter as well as a fertilized control treatment. Large application rates were examined to see if the various compost sources could have a lasting effect on soil C storage, N 2O and CO 2 emissions and corn yields. Compost application significantly increased corn grain yields by 12.9 to 19.4% over 3 yr. However, after 10 yr, FWC was the only compost source which significantly increased yields by 11.3% compared with the fertilized control. Emissions of N 2O and CO 2 varied with compost type, soil water content and time. Greater N 2O emissions occurred in 1999 from PMC (5.4 kg N ha -1) than YWC (2.7 kg N ha -1) and FWC (1.3 kg N ha -1); however, the N 2O emissions from the PMC were less than from YWC and FWC in 2001. The 3-yr average N 2O emissions were significantly greater with PMC (2.7 kg N ha -1) and YWC (2.5 kg N ha -1) compared with the control (1.5 kg N ha -1). Hence, the timing of N 2O emissions varied by compost type, but the overall losses were similar as the higher N 2O losses in the first year with PMC were offset by the reduced losses with PMC in the third year. Significantly more CO 2 was produced from the FWC in 2000 and from PMC in 2001 than the control.
