Monday, November 13, 2006 - 1:45 PM

Effect of Rate and Time of Nitrogen Fertilization on Potato on N2O Emissions.

Bernie Zebarth, Agriculture & Agri-food Canada, P.O. Box 20280, Fredericton, NB E3B 4Z7, CANADA, David Burton, Nova Scotia Agric. College, Truro, NS B2N 5E3, Canada, Karen M. Gillam, Nova Scotia Agricultural College, Department of Environmental Science, PO Box 550, 21 Cox Rd, Truro, NS B2N 5E3, Canada, and John A. MacLeod, Agriculture and AgriFood Canada, Crops and Livestock Research Center, AAFC, 440 University Ave, Charlottetown, PE C1A 4N6, Canada.

There is increased concern over N2O emissions from arable crops such as potato (Solanum tuberosum L.) which receive high fertilizer N inputs. This study examined the effect of the rate and timing of fertilizer N application on potato on N2O emissions in two years. Treatments included a control with no fertilizer N applied, addition of 200 kg N ha-1 banded at planting similar to current grower practice, and split N application with 120 kg N ha-1 banded at planting plus 80 kg N ha-1 banded at final hilling. N2O flux was measured separately in the potato hills and furrows approximately weekly using non-flow-through, non-steady-state chambers. Denitrification rate was measured approximately monthly using the acetylene inhibition method. The pattern of N2O flux over time was consistent with N2O emissions occurring primarily as a result of denitrification. Nitrogen fertilization increased cumulative growing season N2O emissions in both years. Split fertilizer N application had no significant effect on N2O emissions in 2002, but reduced N2O emissions in 2003. This response was attributed to a greater proportion of N2O emissions occurring between planting and hilling in 2003 compared with 2002. Denitrification rate was higher in the furrow compared with the potato hill due to reduced soil aeration, whereas N2O emissions were greater in the potato hill compared with the furrow. These results suggest that there is a need to better understand the factors controlling N2O emissions under field conditions.