1	Nitrous Oxide Emissions from Soils Receiving a Combination of Dairy Manure and Mineral Nitrogen Fertilizer Curtis Dell USDA-ARS-PSWMRU University Park, PA
2	Nitrous Oxide (N₂O) Approximately 300 times more effective than CO₂ as a greenhouse gas Agriculture is a significant contributor By-product of both nitrification (aerobic) and denitrification (anaerobic) Denitrification generally believed to be largest N₂O source in soils, but rates vary greatly depending on soil aeration
3	Manure Management In NE US Large number of dairy, poultry, and swine facilities Limited land base for manure application Water quality problems resulting from excess P accumulations in soil Nutrient management planning required in several NE/Chesapeake Bay states
4	Nutrient Management In NE US Manure application in excess of plant P requirement discouraged/prohibited in many locations A larger land base for spreading or costly waste treatment required Combinations of manure and mineral N fertilizers used more frequently
5	Manure Applications and N₂O Emissions Greater potential for N₂O production when manure is fertilizer source because of addition of organic C Energy source for denitrifying bacteria Stimulates activity by general microbial population, depleting O₂ supply Combinations of organic and mineral N fertilizers may have even greater potential for emissions Organic C from manure and readily available N from mineral fertilizer
6	Objectives Determine if N₂O emissions from a corn field differ when N fertilizer is applied as NH₄NO₃, dairy manure,or a combination of the two.
7	Methods
8	N Source Treatments
9	N Source Treatments All mineral fertilizer 75 kg ha^-1 N as NH₄NO₃:preplant-incorporated 75 kg ha^-1 N as NH₄NO₃: side dress, surface 60 kg ha^-1 mineral P: preplant, incorporated
10	N Source Treatments All mineral fertilizer 75 kg ha^-1 N as NH₄NO₃: preplant-incorporated 75 kg ha^-1 N as NH₄NO₃: side dress, surface 60 kg ha^-1 mineral P: preplant, incorporated P-based manure (31 Mg ha^-1) ~75 kg ha^-1 N as manure: preplant, incorporated 75 kg ha^-1 N as NH₄NO₃: side dress, surface ~60 kg ha^-1 P as manure: preplant, incorporated
11	N Source Treatments All mineral fertilizer 75 kg ha^-1 N as NH₄NO₃: preplant-incorporated 75 kg ha^-1 N as NH₄NO₃: side dress, surface 60 kg ha^-1 mineral P: preplant, incorporated P-based manure (31 Mg ha^-1) ~75 kg ha^-1 N as manure: preplant, incorporated 75 kg ha^-1 N as NH₄NO₃: side dress, surface ~60 kg ha^-1 P as manure: preplant, incorporated N-based manure (62 Mg ha^-1) ~150 kg ha^-1 N as manure: preplant, incorporated ~120 kg ha^-1 P as manure: preplant, incorporated
12	Vented chambers
13	Sampling and Analysis
14	Additional Measurements Gravimetric soil water content Soil inorganic N (2004 only)
15	Results
16	Rainfall
17	Soil Water Content
18	Soil Nitrate: 2004
19	N₂O Emissions: 2003
20	N₂O Emissions: 2004
21	Estimated Seasonal N₂O Emissions
22	Conclusions N₂O emissions are potentially greater when all or part of the N was supplied by manure Application of only manure or a combination of manure and mineral N resulted in similar emissions
23	Implications Utilization of manures as a fertilizer source must be a accounted for in the estimation of N₂O emissions from cropping systems. Application of manure to a larger land base, even at lower rates, has the potential to increase overall annual N₂O emissions.
24	Acknowledgements Bill Priddy, MaryKay Krasinski, Dianna Sturrock, and Jessica Agnew for all their efforts in the field and lab