title: Dairy farm effluent effects on urine patch nitrous oxide and carbon dioxide emissions.
abstract: Dairy farm effluent (DFE) comprises animal feces, urine, and wash-down water collected at the milking shed. This is collected daily during the milking season and sprayed onto grazed dairy pastures. Urine patches in grazed pastures make a significant contribution to anthropogenic N(2)O emissions. The DFE could potentially mitigate N(2)O emissions by influencing the N(2)O to dinitrogen (N(2)) ratio, since it contains water-soluble carbon (WSC). Alternatively, DFE may enhance N(2)O emissions from urine patches. The application of DFE may also provide a substrate for the production of CO(2) in pasture soils. The effects of DFE on the CO(2) and N(2)O emissions from urine patches are unknown. Thus a laboratory experiment was performed where repeated DFE applications were made to repacked soil cores. Dairy farm effluent was applied at 0, 7, or 14 d after urine deposition. The urine was applied once on Day 0. Urine contained (15)N-enriched urea. Measurements of N(2)O, N(2), and carbon dioxide (CO(2)) fluxes, soil pH, and soil inorganic N concentrations were made. After 43 d the DFE had not mitigated N(2)O fluxes from urine patches. A small increase in the N(2)O flux occurred from the urine-treated soils where DFE was applied 1 wk after urine deposition. The amount of WSC applied in the DFE proved to be insignificant compared with the amount of soil C released as CO(2) following urine application. The priming of soil C in urine patches has implications for the understanding of soil C processes in grazed pasture ecosystems and the budgeting of C within these ecosystems.
authors.affiliation: Soil, Plant and Ecological Sciences Division, PO Box 84, Lincoln University, Canterbury, New Zealand. clought@lincoln.ac.nz
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Clough
authors.forename: Francis M
authors.initials: FM
authors.lastname: Kelliher
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000032:analysis*; D002417:Cattle; D003612:Dairying; D017753:Ecosystem; D009609:Nitrous Oxide / Q000032:analysis*; D012987:Soil; D014556:Urine; D014835:Volatilization; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D009609:Nitrous Oxide