Fræðaþing landbúnaðarins - 08.02.2008, Page 540

538 | FRÆÐAÞING LANDBÚNAÐARINS 5, 2008
which can be oxidized into the nitrate form (NO3') via the process called nitrification
(NH4+ NO2' NO3'). Plant roots mainly take up nitrogen in the form of NH4+ or
NO3' ions. Denitrification occurs when oxidized forms of nitrogen such as NO3" and NO2'
are converted to dinitrogen (N2). In this process some amounts of nitrous oxide gas (N2O)
can be released as a by product by the following sequence: NO3' “^NO^’ “^NO “^N20
-^N2 (Brady and Weil, 1999; Minami, 2002).
Land use management
Anthropogenic activity in the form of land use management can affect the namral
occurring bacteria to increase/decrease the decomposition rate and affect the production
of the green house gases, N^O, C02 and CH4 (Freney, 2002; Brady and Weil, 1999). On a
global scale, agriculture is a major contributor to N20 emission where soils are the major
source (Prather et al., 2001). Land use management must be seen in a broad perspective.
The net effects of activities related to land use, land use change and forestry (LULUCF)
depends on all activities involved (Sampson and Scholes, 2000).
The objectives of the study
The objectives in this study are to obtain data on the release of three important GHG’s
from organic soil cores in Iceland with different land use management and at different
temperatures and at different water table levels. The study will emphasize on the N20
emission. To be able to predict the magnitude and effects of the anthropogenic impacts
through different agricultural land use management, it is necessary to collect data from
microbial respiration and the resulting soil greenhouse gas emission. Data on the
emission factors for the relevant gases and land use management systems will improve
the quality of information from Icelandic agricultural land use management to the
UNFCCC on greenhouse gas release. The study is ongoing and final results will be
published before the end of 2008.
Materials and methods
Temperature
Twenty four soil cores were collected (2006) from nine study sites divided into three
main land use managements located in Borgaríjöróur region, in West Iceland. The three
land use managements are: '* undisturbed peat land, 2) drained peat land and 3) fertilized
hay field on drained peat land.
The measurements were performed in controlled laboratory conditions. All vegetation
was removed on the top of the soil cores (5 cm) except from six of the cores where the
vegetation was kept naturally (named “G”). All the soil cores were adjusted to the same
water level, 30 cm from surface for the hay field and the drained peat land cores, and a 2
cm water level for the undisturbed peat land cores. The soil cores were 50 cm long and 10
cm diameter and made of PVC pipes. Additionally, on the top of the soil cores pipe was
an 8 cm air filled gas collection chamber. The gas emission was collected with a syringe
fforn the headspace on the top of the soil core. Gas samples (2 ml) were collected fforn
each soil core and the content of N20 and CH4 were determined with a Varian CP-3800
gas chromatograph (Varian, Inc.) and C02 was measured with an LI-6250 C02 analyzer
(Li-COR Inc.). Data of the emissions from controlled laboratory conditions was collected
at different temperatures, i.e. 3°C, 8°C, 13°C and 18°C respectively.