|
| |
|
| |
|
| |
|
|
N.sub.2./sub.O and N.sub.2./sub. emissions, denitrification activity and the size of the denitrifying community in a pasture soil – what is the role of pH?
Čuhel, Jiří ; Šimek, Miloslav ; Laughlin, R.J. ; Chéneby, D. ; Bru, D. ; Philippot, L.
Denitrification and subsequent N emissions are significantly influenced by soil pH. Nevertheless, it is not clear, whether pH controls denitrification only due to the influence on kinetics of denitrification enzymes or also due to the different structure of denitrifiers. The objective of the present study was to compare results from N gas emissions and N.sub.2./sub.O molar ratio from soils with artificially changed pH, with those obtained from potential denitrification, and to find out whether there is a relationship between N fluxes and abundance of denitrifiers. The experimental site was located in a grassland area at Borová Farm near Český Krumlov, Czech Republic, and consisted of 12 plots (3x3 m) amended with KOH solution (pH alkaline), H.sub.2./sub.SO.sub.4./sub. solution (pH acidic) or with no amendments (pH natural). The .sup.15./sup.N gas flux method was used to quantify emissions of N.sub.2./sub.O and N.sub.2./sub. in situ at intervals over 74 H.
|
|
|
Nitrogen and carbon transformation processes in soil in permanent grasslands - research in cattle overwintering area
Šimek, Miloslav ; Hynšt, Jaroslav ; Čuhel, Jiří ; Elhottová, Dana ; Chroňáková, Alica ; Němcová, Anna ; Jirout, Jiří ; Krištůfek, Václav
Agricultural soils represent a significant source of greenhouse gases (carbon dioxide, nitrous oxide and methane). Pasture soils and especially overwintering areas receive large amounts of nutrients as animal excrements. Together with other effects, this creates good conditions for high rates of nitrogen and carbon transformations, and also for substantial losses in the form of gaseous metabolites. This paper informs on research of a specific model ecosystem – the cattle overwintering area. Research is focused either on the structure of soil microbial community and on its activities including the formation of gases in, and their emission from the soil to atmosphere.
|
|
|
Quantification of key genes in nitrification and denitrification
Chroňáková, Alica ; Čuhel, Jiří ; Radl, V. ; Elhottová, Dana ; Šimek, Miloslav
The objective of the study was to explore the long-term effect of cattle grazing activities on abundance of nitrifying and denitrifying communities on overwintering area. The abundances of studied populations were determined using qPCR method and copy numbers of .i.amoA, nirS,./i. and .i.nirK./i. genes were quantified in spring and fall. High input of cattle urine and excrements with other animal activities had a significant impact on abundance of nitrifying and denitrifying bacteria, being higher in cattle impacted soils in comparison to control. Our data also showed that abundance of both bacterial communities reflected seasonal changes.
|
|
| |
|
|
Emissions of greenhouse gases (N2O and CO2) from pasture soil as a result of activity of soil microbial community - preliminary results
Šimek, Miloslav ; Hynšt, Jaroslav ; Brůček, Petr ; Čuhel, Jiří
Cattle overwintering area was shown an important point source of N2O and CO2. The emissions of N2O were mostly directly related to the rate of animal impact as the greatest fluxes of N2O and the highest total cumulative N2O emissions as well were found at the most impacted site. The fluxes of N2O were however very variable in time and most of N2O was emitted during several short events in spring or in winter. Laboratory experiments suggested that total amount of nitrogen escaping from soil from impacted sites is much greater than indicated by field measurements of N2O fluxes and molecular nitrogen (N2) was shown as the main nitrogen gas. It is hypothesized that soil pH is a crucial soil factor controlling the mole fraction of N2O: under slightly alkaline conditions in severely impacted soils, denitrification is completed and most of nitrogen escapes from the soil as N2; under more acidic conditions, however, the activity of nitrous oxide reductase is partly reduced.
|
|
|
Dynamics of N2O emissions after C and N amendments of soil at the cattle overwintering area
Hynšt, Jaroslav ; Brůček, Petr ; Čuhel, Jiří ; Šimek, Miloslav
Field experiments were carried out at the cattle overwintering area in South Bohemia, Czech Republic, focused on the emissions of N2O after soil amendments with nitrate and glucose. Emissions were estimated using a permanent static chamber technique. Nitrate and glucose amendments caused very sharp increases of N2O fluxes, which however diminished after 2-3 days. Total amount of N2O escaping the soil was related to the amount of N and C added, and was calculated to 1-15 kg N.ha-1 (0.2-3% of N applied). Emissions were heterogeneous, which is shown by great differences among the individual chambers. Emissions were variable in time and very probably were controlled by temperature, as they approximately followed the air and surface soil temperature patterns. Despite the timing of amendment application, peaks of emissions were always determined 6 hours after the amendments.
|
guest ::
RSS feed.