Field studies were conducted to assess the spatial and
temporal variability of nitrous oxide (N2O) emissions in an
agricultural field cropped to onion in Mikassa, northern Hokkaido (Japan).
N2O emissions measurements were conducted in 100 by 100 m and
60 by 60 m grids in 1999 and 2000, respectively with samples taken at
10 m spacing. Air samples for N2O determinations were collected
using the closed-chamber technique. The chambers were circular with steel
frames. The top of each chamber had a gas sampling tube and a bag to control
air pressure inside. The height and diameter of the chamber were 0.35
and 0.30 m, respectively. Air samples were stored in vial bottles for
analysis with a gas chromatograph with electron capture detector within
24 h after sampling. GS+ 7.0 geostatistical software and statistix 8.0
were used for data analysis. Results showed that N2O emissions
were highest in 1999 as compared to 2000. N2O emissions were
fitted to a linear variogram in 1999 and responded to a spherical variogram
model in 2000. Positive first degree surface trends were also found for
N2O emissions data in both years. However, the removal of these
trends did not change variogram models, but significantly improved them
by increasing the R2 and Q values. N2O emissions
systematically varied with small zones of uptake (negative flux) across
the field, suggesting the presence of hot spots.
Nsalambi V. Nkongolo, Kanta Kuramochi and Hatano Ryusuke, 2009. Nitrous Oxide (N2O) Emissions from a Japanese Lowland
Soil Cropped to Onion: I. Spatial and Temporal Variability of Fluxes. International Journal of Agricultural Research, 4: 17-28.