21 Feb 2022
21 Feb 2022
Status: a revised version of this preprint is currently under review for the journal BG.

Episodic N2O emissions following tillage of a legume-grass cover crop mixture

Alison Bressler and Jennifer Blesh Alison Bressler and Jennifer Blesh
  • School for Environment and Sustainability, University of Michigan, Ann Arbor, 48104, USA

Abstract. Nitrogen fertilizer inputs to agricultural soils are a leading cause of nitrous oxide (N2O) emissions in the U.S. Legume cover crops are an alternative N source that can reduce agricultural N2O emissions compared to fertilizer N. However, our understanding of episodic N2O flux following cover crop incorporation by tillage is limited and has focused on single species cover crops. Our study explores whether increasing cover crop functional diversity with a legume-grass mixture can reduce pulse emissions of N2O following tillage. In a field experiment, we planted crimson clover (Trifolium incarnatum L.), cereal rye (Secale cereal L.), a clover-rye mixture, and a no-cover control at two field sites with contrasting soil fertility properties in Michigan. We hypothesized that N2O flux following tillage of the cover crops would be lower in the mixture and rye compared to the clover treatment, because rye litter can decrease N mineralization rates. We measured N2O for approximately two weeks following tillage to capture the first peak of N2O emissions in each site. Across cover crop treatments, the higher fertility site, CF, had greater cover crop biomass, twofold higher aboveground biomass N, and higher cumulative N2O emissions than the lower fertility site, KBS (413 ± 67.5 g N2O-N ha−1 vs. 230 ± 42.5 g N2O-N ha−1; P = 0.0037). There was a significant treatment effect on daily emissions at both sites. At CF, N2O fluxes were higher following clover than the control 6 days after tillage. At KBS, fluxes from the mixture were higher than rye 8 and 11 days after tillage. When controlling for soil fertility properties across sites, clover and mixture led to approximately twofold higher N2O emissions compared to rye and fallow treatments. We found partial support for our hypothesis that N2O would be lower following incorporation of the mixture than clover. However, treatment patterns differed by site, suggesting that interactions between cover crop functional types and background soil fertility influence N2O emissions during cover crop decomposition.

Alison Bressler and Jennifer Blesh

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-39', Anonymous Referee #1, 24 Feb 2022
    • AC1: 'Reply on RC1', Alison Bressler, 31 Mar 2022
  • RC2: 'Comment on bg-2022-39', Anonymous Referee #2, 02 Mar 2022
    • AC2: 'Reply on RC2', Alison Bressler, 31 Mar 2022

Alison Bressler and Jennifer Blesh

Alison Bressler and Jennifer Blesh


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Latest update: 26 May 2022
Short summary
Our field experiment tested if a mixture of a nitrogen fixing legume and non-legume cover crop could reduce nitrous oxide (N2O) emissions following tillage, compared to the legume grown alone. We found higher N2O following both legume treatments, compared to those without, and lower emissions from the cover crop mixture at one of the two test sites, suggesting that interactions between cover crop types and soil quality influence N2O emissions.