Overwinter and Growing Season Nitrous Oxide Emissions from Cattle Excrement and Bedding.

Nitrous oxide emissions from excrement and bedding of cattle is not well understood. Further, emissions during winter from excrement and bedding in very cold temperate climates are not known. We conducted a series of experiments determining nitrous oxide emissions from cattle feces, urine and simulated solid manure (excrement plus bedding) deposited on grassland in winter and early summer. Monitoring has also been conducted on bedding packs of pen-confined cattle. Emissions from excrement deposited in early summer or mid-summer were relegated to several weeks following addition when moisture conditions were suitable for nitrous oxide production. Urine produced 10-fold higher emissions than feces. Compared to pig slurry manure added to grassland, emissions estimated for deposited excrement of cattle grazing the grassland were a tenth of those from the slurry. Emissions from simulated solid manure were much lower than from feces and urine alone. Deposition of excrement and simulated solid manure in winter resulted in no winter emissions because of frozen conditions and little emissions in spring and early summer because of snow melt redistribution of urine and feces nitrogen from point of placement. Overwinter emissions of nitrous oxide from bedding packs were not detected, though ammonia emissions were. Nitrous oxide emissions increased once packs thawed and into warming of summer.