Emissions of nitrous oxide and methane from pasture soils

 Miloslav Šimek, Petr Brůček, Jiří Čuhel, Dana Elhottová, Jaroslav Hynšt, Alica Chroňáková, Václav Krištůfek, Anna Němcová, Hana Šantrůčková, Eva Uhlířová

Nitrous oxide and methane are important so called greenhouse gases which also participate in ozone destruction in stratosphere. Microbial transformations of nitrogen and carbon in soil represent one of major sources of these gases. Pasture soils including cattle overwintering areas were identified as significant source of nitrous oxide as well as methane. High density of animals, accumulation of excrements and changes in soil structure are responsible for production of large quantities of gases subsequently escaping into the atmosphere. Nitrogen and other nutrients accumulate in soil during winter and they are later intensively metabolised by soil microorganisms producing gases especially at favourable conditions (temperature, soil moisture etc.) in spring period when most of the emissions take place, too. This results not only in large nutrient loses from soil but also in a significant pollution of atmosphere by nitrous oxide, methane and other trace gases. An important result of our research, taking into account practical possibilities of reducing nitrous oxide emission, is the finding that nitrous oxide emissions are likely affected by soil pH: at higher pH they decrease relatively while the proportion of harmless molecular nitrogen increases. We also investigate intensively the production of methane by archaeal methanogenes and oxidation of methane in surface soil layer using latest methods and techniques of molecular biology. During last 5 years the results were published in ca 20 publications including 5 in international journals and presented in other 16 contributions at 8 international conferences.

Accumulation of animals in pasture sites creates conditions for acceleration of soil microbial processes and leads to the emissions of greenhouse gases from soils to the atmosphere. Agricultural soils represent a significant source of nitrous oxide and methane emissions.

Gas emissions from soils are regulated by a number of environmental factors. Soil porosity and water content in soil pores represent important regulatory factors. The picture shows determination of water infiltration rate into the pasture soil; chambers for gas flux measurements can be seen in the background.