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

ABSTRACT

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)₂SO₄. 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.

KEYWORDS:

• Ammonium
• denitrification
• incubation experiment
• nitrate
• organic matter amendment

Acknowledgments

I thank Dr. Hideo Kubotera, Kyushu Okinawa Agricultural Research Center, NARO (now at Institute for Agro-Environmental Sciences, NARO) for help in the experimental design.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financed by the National Agriculture and Food Research Organization of Japan and was supported by a grant for “Development of mitigation and adaptation techniques to global warming in the sectors of agriculture, forestry, and fisheries” from the Ministry of Agriculture, Forestry, and Fisheries of Japan.