Nitrous oxide emission as affected by tillage, corn-soybean-alfalfa rotations and nitrogen fertilization

Nitrous oxide (N 2 O) produced from agricultural activities represents a threat to the ozone layer and economic losses. Rates and magnitudes of N 2 O emissions of cropping systems must be determined to establish corrective management procedures. In 1994, N 2 O emissions were determined with corn (ZeaMays L.) and corn-legume rotations. Continuous corn was studied on four soils, two from a long-term experiment, a Ste. Rosalie heavy clay (Humic Gleysol) and a Chicot sandy loam (Grey-Brown Podzol), at 0, 170, 285 or 400 kg N ha −1 , and two from a corn rotation study, a Ste. Rosalie clay (Humic Gleysol) and an Ormstown silty clay loam (Humic Gleysol). Treatments included no-till (NT) and conventional tillage (CT), monoculture corn (CCCC), monoculture soybean; corn-soybean; and soybean-corn-alfalfa phased rotations. Nitrogen rates of 0, 90, or 180 kg N ha −1 for corn and 0, 20, or 40 kg N ha −1 for continuous soybean were used, and soybean/alfalfa following corn no fertilizer N. Rates of N 2 O emission were measured from closed chambers through the growing season. About 0.99 to 2.1% of N added was lost as N 2 O. Nitrous oxide emission increased with increased soil water content, NO 3 concentration and fertilizer N rates. Emission of N 2 O was higher with NT than with CT, and with corn than with soybean or alfalfa. A corn system using CT, legumes in rotation and moderate fertilizer N would reduce N 2 O emission.