Effects of pellet inorganic nitrogen on nitrous oxide emissions from cattle manure compost pellets

Manure compost pellets (MCPs) emit more nitrous oxide (N2O) when applied to soils than loose manure compost or inorganic fertilizer, but pellets of N-enriched manure compost (N+MCP), a by-product of deodorizing manure during composting, emit less N2O than MCPs. To investigate why N+MCPs emit less N2O than MCPs, I studied the effect of inorganic N content, which differs clearly between MCP (2 mg NO3- g(-1), 0.2 mg NH4+ g(-1)) and N+MCP (17 mg NO3- g(-1), 4 mg NH4+ g(-1)). MCPs made from cattle manure composts were incubated with various concentrations of nitrate-N (2, 3.5, 5, 10, 20 mg g(-1)) as KNO3 and ammonium-N (0, 2, 4 mg g(-1)) as (NH4)(2)SO4. N2O emissions and related chemical properties were measured during incubation for 14 days. N2O emission peaked at 1 day, and the peak height was significantly lower when nitrate (MCP-NO3_20) and nitrate plus ammonium (MCP-NO3+NH4) contents were raised to the same levels as in N+MCP than in MCP (no added N). Nitrite contents in pellets at 1 day were also lower in both treatments than in MCP. Total N2O emissions during incubation were significantly lower from MCP-NO3+NH4 than from MCP. Emission factors of MCP-NO3_20 and MCP-NO3+NH4 were significantly lower than that of MCP. Pellet nitrate content was negatively correlated with total N2O emission during incubation (p < 0.05). These results suggest that the inorganic N content is important in suppressing N2O emissions from N+MCP.