TY - JOUR

T1 - Flooding-induced N2O emission bursts controlled by pH and nitrate in agricultural soils

AU - Hansen, Mette

AU - Clough, Tim J.

AU - Elberling, Bo

PY - 2014

Y1 - 2014

N2 - Agricultural soils are a major source of the greenhouse gas nitrous oxide (N2O) to the atmosphere. Increasing frequency and severity of flooding as predicted for large intensively cropped areas may promote temporary denitrification and N2O production but the effect of flooding events on N2O emissions is poorly studied for agricultural systems. The overall N2O dynamics during flooding of an agricultural soil and the effect of pH and NO3− concentration has been investigated based on a combination of the use of microsensors, stable isotope techniques, KCl extractions and modelling. This study shows that non-steady state peak N2O emission events during flooding might potentially be at least in the order of reported annual mean N2O emissions, which typically do not include flood induced N2O emissions, and that more than one-third of the produced N2O in the soil is not emitted but consumed within the soil. The magnitude of the emissions are, not surprisingly, positively correlated with the soil NO3− concentration but also negatively correlated with liming (neutral pH). The redox potential of the soil is found to influence N2O accumulation as the production and consumption of N2O occurs in narrow redox windows where the redox range levels are negatively correlated with the pH. This study highlights the potential importance of N2O bursts associated with flooding and infers that annual N2O emission estimates for tilled agricultural soils that are temporarily flooded will be underestimated. Furthermore, this study shows that subsurface N2O reduction is a key process limiting N2O emission and that a reduction in N2O emissions is achievable if highly fertilized N-rich soils are limed.

AB - Agricultural soils are a major source of the greenhouse gas nitrous oxide (N2O) to the atmosphere. Increasing frequency and severity of flooding as predicted for large intensively cropped areas may promote temporary denitrification and N2O production but the effect of flooding events on N2O emissions is poorly studied for agricultural systems. The overall N2O dynamics during flooding of an agricultural soil and the effect of pH and NO3− concentration has been investigated based on a combination of the use of microsensors, stable isotope techniques, KCl extractions and modelling. This study shows that non-steady state peak N2O emission events during flooding might potentially be at least in the order of reported annual mean N2O emissions, which typically do not include flood induced N2O emissions, and that more than one-third of the produced N2O in the soil is not emitted but consumed within the soil. The magnitude of the emissions are, not surprisingly, positively correlated with the soil NO3− concentration but also negatively correlated with liming (neutral pH). The redox potential of the soil is found to influence N2O accumulation as the production and consumption of N2O occurs in narrow redox windows where the redox range levels are negatively correlated with the pH. This study highlights the potential importance of N2O bursts associated with flooding and infers that annual N2O emission estimates for tilled agricultural soils that are temporarily flooded will be underestimated. Furthermore, this study shows that subsurface N2O reduction is a key process limiting N2O emission and that a reduction in N2O emissions is achievable if highly fertilized N-rich soils are limed.

KW - N2O

KW - Flooding

KW - Denitrification

KW - Dissimilatory NO3- reduction to ammonium (DNRA)

KW - Agriculture

KW - Microsensor

KW - Stabile isotope

U2 - 10.1016/j.soilbio.2013.10.031

DO - 10.1016/j.soilbio.2013.10.031

M3 - Journal article

VL - 69

SP - 17

EP - 24

JO - Soil Biology & Biochemistry

JF - Soil Biology & Biochemistry

SN - 0038-0717

ER -