Browsing by Subject "N2O"

Plenty of CO2 is commonly emitted from cultivated peat soils and substantial N2O emissions have occasionally been measured from acid sulphate soils. The factors limiting the emission of CO2 and N2O from the different layers of organic acid sulphate soil in Pärnänsuo were studied by aerobic and anaerobic incubation experiments. Two topsoil peat layers (upper and lower) and two mineral soil layers (upper and lower) were investigated. An aerobic experiment was carried out to see the emission of CO2 and N2O after application of glucose and ammonium, at two different temperatures (5o and 20o C). The water content of the soils was adjusted to 60% water- filled pore space (WFPS). Anaerobic experiment was carried out to assess the denitrification potential of different layers and the effect of glucose and nitrate alone and in combination as at 20oC using the acetylene inhibition technique. The lower peat layer exhibited more CO2 emission comparing to upper peat in the aerobic experiment. Additionally, in both peat layers and upper mineral soil layer, CO2 emission was increased exceedingly after glucose application. In the anaerobic experiment, potential denitrification from the upper peat was significantly higher than from other soil layers. Besides, the soil layers responded differently to C and N application. N2O emission from the upper peat was limited by easily available C whether it was applied as glucose alone or, in the presence of nitrate. On the contrary, N2O emission from lower peat layer was limited by nitrate with or, without glucose, but not by glucose alone. Both upper and lower mineral soil denitrification was limited by nitrate without glucose or, in combined with glucose, and not by glucose alone. Nitrogen mineralization pattern was different in upper and lower peat. A very high amount of NO3- was found in the upper peat, while there was a high amount of NH4+ in lower peat. Both the NO3- and NH4+ showed an increasing trend in lower mineral comparing to upper mineral, depicting an exceedingly high amount of mineral N at deeper layers

Aim of this thesis was to study the quantity of nitrous oxide (N2O) emissions from pea in a multiple-year experiment in Haltiala, Helsinki, in growing seasons 2020–2022 in Leg4Life project’s field trial (2020–2024). The experiment was conducted as a randomized complete block design (RCBD) with four replicates. There were ten (10) different treatments including one (1) fallow. Treatments were different pea crop rotations with fertilized monoculture grown pea (20 kg N ha-1) and fertilized monoculture grown oat (90 kg N ha-1) as a control treatments. Treatments were 1 (fallow – fallow – fallow), 2 (pea 20– pea 20 – pea 20), 3 (oat 90 – oat 90 – oat 90), 4 (pea 20 – spring wheat 90 – pea 20), 5 (pea-rapeseed 20–20 – oat 0 – pea 20), 6 (pea-rapeseed 20–20 – oat 90 – pea 20), 7 (pea 20 – winter wheat 90 – rapeseed 90), 8 (pea 20 – rapeseed 0 – spring wheat 90), 9 (pea 20 – rapeseed 90 – spring wheat 90) and 10 (pea 20 – oat 90 – rapeseed 90). Nitrogen fertilization levels were either 20, 40 or 90 kg ha-1. Gas emission samples were measured in field from closed chambers by taking three samples in 20 minutes interval from treatments 1, 2, 3, 5, 6, 8 and 9. Samples were analysed in gas chromatograph. Statistical analyses were made by analysis of variance (ANOVA). Statistically significant differences in means were located by using a t-test (LSD) Results were not statistically different from each other except fallow (treatment 1) in 2020 and spring wheat (treatment 8) in 2022 which caused statistically significant higher N2O-emissions compared to other treatments. Cumulative N2O-emissions from three years were not statistically different from each other except treatment 8 (pea 20 – rapeseed 0 – spring wheat 90), which differed all other crop rotation treatments but not treatment 1 (fallow – fallow – fallow). Cultivation of pea did not cause significantly higher N2O-emissions than oat or spring wheat. Catch crop did not have effect on emissions either. Dry matter and nitrogen yield-scaled N2O-emissions from pea treatments were not significantly higher when compared to other treatments except in 2021 when dry matter yield-scaled N2O-emissions from pea (treatment 2, pea 20) were significantly higher than those in oats (treatments 3, 5 and 6, oat 90, oat 0 and oat 90). Dry matter yield-scaled N2O-emissions were 1.0 and 0.3 g N2O-N kg-1 aboveground biomass respectively.

Nitrous oxide (N2O) is an important greenhouse gas with a lifetime of 121 years and radiative efficiency of 219 times that of carbon dioxide (CO2). Nitrous oxide concentration has increased in the atmosphere from the 1800’s, in recent decades with increasing rate. Pristine mires have detected to have small N2O emissions, but drained peatlands are a major source of anthropogenic N2O emissions. Peatland restoration has been detected to be a tool for climate change mitigation. Peatlands act as a major carbon storage and carbon balance of pristine and drained peatlands has been widely studied. Nitrous oxide is one of the major peatland related greenhouse gases but has not been studied as intensively from restored peatlands in the boreal zone. Peatland restoration area has increased in Finland in recent decades due to biodiversity conservation and climate change mitigation. The total impact of peatland restoration on all greenhouse gas emissions has not been thoroughly studied. Nitrous oxide has received less attention than methane (CH4) and carbon dioxide. This thesis aims to gain more information on N2O emissions from restored peatlands and evaluate which factors affect the emissions. N2O flux data from 25 restored peatlands from Southern and Central Finland was analysed. The data was collected during May–August of 2022 from forestry-drained restored peatlands. Measurements were conducted on former strips and ditches of restored peatlands. Measurement sites had been divided into drained peatland forest types according to vegetation. The research indicates that N2O fluxes from rewetted, forestry-drained peatlands centre to small positive and negative values. Variation is wider than with pristine mires, but mean values for this measurement period were not significantly higher. Drained peatland forest type had a weak impact on N2O emissions, nutrient-rich sites had higher mean N2O emissions compared to less fertile sites of the study. Highest N2O emissions were measured from nutrient-rich site ditches. Less fertile sites of the study acted as a net sink of N2O on both strip and ditch. Environmental factors as water table (WT) level and soil temperature had an impact on N2O emissions, thus WT level as the only individual explanatory variable explained the variation in N2O emissions the most. N2O emission seemed to slightly decrease with years passing since restoration activities. This trend was the most visible with nutrient-rich sites. C/N ratio had a slight negative trend with site mean N2O emissions on both strip and ditch during the measurement season. Future research is needed to understand the dynamics of higher spatial and temporal N2O emissions.