posted on 2024-02-08, 11:43authored byXiaotong Song, John Parker, Stephanie K. Jones, Limei Zhang, Ian Bingham, Robert M. Rees, Xiaotang Ju
Labile carbon (C) continuously delivered
from the rhizosphere profoundly
affects terrestrial nitrogen (N) cycling. However, nitrous oxide (N2O) and dinitrogen (N2) 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 15N tracers to investigate N2O
and N2 emissions in agricultural soils with pH and organic
C (SOC) gradients. A significantly negative exponential relationship
existed between N2O and N2 emissions under continuous
C exudation. Increasing soil pH significantly promoted N2 emissions while reducing N2O emissions. Higher SOC further
promoted N2 emissions in alkaline soils. Native soil-N
(versus fertilizer-N) was the main source of N2O (average
67%) and N2 (average 80%) emissions across all tested soils.
Our study revealed the overlooked high N2 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 N2O and N2 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.