Nitrous oxide emissions from soil amended with glucose, alfalfa, or corn residues

Abstract

Nitrous oxide (N2O) emissions result from the nitrification and denitrification processes, the latter strongly affected by soil organic carbon (C) derived from plant residues. This study addressed two questions: (1) does plant residue C become less available to denitrifiers after a period of aerobic incubation, and (2) do plant residues with smaller particle sizes provide C for higher rates of N2O production due to a faster decomposition rate? Nitrous oxide fluxes from soil amended with alfalfa or corn residues, or glucose were measured in the laboratory using a gas flow‐through chamber system. Soil amended with these C substrates was also subjected to a 5‐d aerobic preincubation treatment. The significance of particle size on C availability was studied by comparing N2O released from soil amended with ground (particle size <1 mm) and large pieces (5‐cm lengths) of alfalfa residues. A 5‐d aerobic preincubation of soil amended with plant residues resulted in reduced N2O production during a subsequent anaerobic period. Results suggested that, due to consumption of the most available substrate, remaining C in plant residues is less available to denitrifiers after a period of aerobic incubation. Higher N2O losses were found with large alfalfa particles than with ground alfalfa.