Labile Carbon from Artificial Roots Alters the Patterns of N 2 O and N 2 Production in Agricultural Soils

• Published in: Environmental science & technology
• Main Authors: Song, Xiaotong, Parker, John, Jones, Stephanie K, Zhang, Limei, Bingham, Ian, Rees, Robert M, Ju, Xiaotang
• Format: Journal Article
• Language: English
• Published: United States 08-02-2024
• Subjects: N2O; 15N-labeled urea; N2; artificial root; soil pH; continuous labile C addition
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.3c10833

Labile carbon (C) continuously delivered from the rhizosphere profoundly affects terrestrial nitrogen (N) cycling. However, nitrous oxide (N
O) and dinitrogen (N
) production in agricultural soils in the presence of continuous root C exudation with applied N remains poorly understood. We conducted an incubation experiment using artificial roots to continuously deliver small-dose labile C combined with
N tracers to investigate N
O and N
emissions in agricultural soils with pH and organic C (SOC) gradients. A significantly negative exponential relationship existed between N
O and N
emissions under continuous C exudation. Increasing soil pH significantly promoted N
emissions while reducing N
O emissions. Higher SOC further promoted N
emissions in alkaline soils. Native soil-N (versus fertilizer-N) was the main source of N
O (average 67%) and N
(average 80%) emissions across all tested soils. Our study revealed the overlooked high N
emissions, mainly derived from native soil-N and strengthened by increasing soil pH, under relatively real-world conditions with continuous root C exudation. This highlights the important role of N
O and N
production from native soil-N in terrestrial N cycling when there is a continuous C supply (e.g., plant-root exudate) and helps mitigate emissions and constrain global budgets of the two concerned nitrogenous gases.