Mondays in Microbiolgy

Theme: Greenhouse gas emissions in agriculture

Date: 27 February 2023
Time: 15.30-16.30

Chairpersons: Associate Professor Mette Burmølle (DMS) and Professor Carsten Suhr Jacobsen


“Nitrification – a niche microbial process impacting GHG production – a mRNA study”
by Carsten Suhr Jacobsen,
Professor and Head of Department of Environmental Sciences, Aarhus University, RISØ Campus

"Effects of greenhouse gas emission mitigation measures on soil microorganisms"
by Anne Winding,
Professor in molecular microbial ecology at Department of Environmental Science, Aarhus University

"Spatial and temporal variations of nitrous oxide emissions in coffee agroforestry systems in Costa Rica"
by Anders Priemé,
Professor in microbial ecology at Department of Biology, University of Copenhagen

"Microbial controls of methane and nitrous oxide emissions in agroecosystems"
By Søren O. Petersen,
Professor at Department of Agroecology, Aarhus University


Carsten Suhr Jacobsen

Professor and Head of Department of Environmental Sciences, Aarhus University, RISØ Campus

Anne Winding
Department of Environmental Science, Aarhus University, Denmark.

I am professor in molecular microbial ecology at Department of Environmental Science, Aarhus University, Denmark. My research focuses on how soil microbial communities, their immense diversity and interactions within the microbiome and with invertebrates can i) reduce greenhouse gas emissions from the soil environment and ii) benefit sustainable crop production in optimizing the rhizosphere microbiome and minimize anthropogenic effects. In addition, risk assessing anthropogenic initiatives like soil amendment with chemical or living organisms as microbial pest control agents are investigated. 

Soil microorganisms are increasingly recognized for their importance of soil health and crop production, and increasing attention is devoted to soil microbial biodiversity and quality and how this can sustain healthy and productive soil. At the same time different mitigation strategies are considered to reduce the greenhouse gas emission from Danish agriculture. This includes widespread use of nitrification inhibitors (NI) to reduce nitrous oxide (N2O) emission and biochar to sequester carbon and potentially reduce N2O and CH4 emissions. These mitigation strategies might have non-target effects on the soil microbial communities and hence effects on soil quality and crop production. 
N2O is a potent greenhouse gas produced by microbial conversion of ammonia or nitrate, and these compounds can easily be lost from the plant root zone. NI reduce conversion of NH4+ to NO3-, and thereby retain the ammonium form available for the plants for a longer time in the soil. However, knowledge on non-target effects of NI on the indigenous soil organisms is limited. We tested the effects of NI on soil microbial communities when NI combined with three fertilizers were applied to field plots at two locations with different soil types in two growing seasons of spring barley and winter wheat, respectively, in conventional tillage and no tillage systems. Differences between both growth seasons, the two agricultural sites and type of fertilizer were observed, and the tillage regime affected the microbial communities significantly. Effects of NI on the microbial functional response profile and eDNA analyses were limited to fungal community diversities. 

Anders Priemé
Professor in microbial ecology at Department of Biology, University of Copenhagen

I mainly study the activity, abundance and diversity of soil bacteria and fungi and how these are affected by global change and feedback to global climate.

Coffee is the most intensively traded tropical agricultural commodity and is commercially cultivated in more than 50 countries in sub- and tropical areas. Costa Rican coffee plantations generally receive high nitrogen inputs (150 and 350 kg N ha-1 yr-1) through synthetic N fertilizers. This study is the first to focus on both spatial and high-resolution temporal trends in N2O emissions and a seasonal N2O budget for a tropical agricultural system. We combined (i) multi-year continuous dynamic chamber measurements from Costa Rican coffee-growing sites with different fertilisation levels, (ii) static chamber measurements along a typical sloping coffee field, and (iii) measurements from a laboratory incubation experiment with nutrient addition to different soil types. We found that annual N2O fluxes were dominated by bursts over few weeks following N-fertilisation. Large differences in N2O emissions along a topographic gradient could be explained by nitrate transport downhill and flooded conditions favouring denitrification at the bottom of the slope. Incubation experiments indicated that denitrification was the main process controlling N2O emissions. We conclude that N2O emissions from the coffee agroforestry systems were generally low considering the large N input, but may be underestimated, as both poorly drained depressions functioning as N2O hotspots as well as temporal N2O bursts need to be taken into account.

Søren O. Petersen
Professor at the Department of Agroecology, Aarhus University

Our Department provides applied and strategic research on many aspects of agricultural production and its environmental impacts. I study the microbial ecology of soil and manure environments with a main focus on the regulation of methane and nitrous oxide emissions, and how this may translate into mitigation strategies. 

Agriculture is the main source of anthropogenic emissions of methane and nitrous oxide in Denmark. Microbial interactions regulate the emission of both gases in manure and soil environments, and understanding these interactions is key to predict, and mitigate, emissions. Livestock production is dominated by liquid manure management, and storages are important point sources of methane. Methanotrophs inhabit natural surface crusts, and studies of their characteristics has been used to investigate a novel mitigation technology. Manure recycling for crop production, and cover crops outside the growing season, are strategies to reduce N surplus and environmental losses. But manure and residues both constitute organic hotspots that may be more important sources of nitrous oxide than synthetic fertilisers in light-textured soil. Organic hotspots are characterised by intense microbial activity and population dynamics in gradients of oxygen and reactive C and N that are temporally stable, but sensitive to gas and solute diffusivity. Uncoupling nitrification and denitrification in this gradient environment is an effective mitigation strategy.