Spatial Variability of Nitrous Oxide Emissions and Their Soil-Related Determining Factors in an Agricultural Field
2003
Yanai, Junta | Sawamoto, Takuji | Oe, Taku | Kusa, Kanako | Yamakawa, Keisuke | Sakamoto, Kazunori | Naganawa, Takahiko | Inubushi, Kazuyuki | Hatano, Ryusuke | Kosaki, Takashi
To evaluate spatial variability of nitrous oxide (N₂O) emissions and to elucidate their determining factors on a field-scale basis, N₂O fluxes and various soil properties were evaluated in a 100- × 100-m onion (Allium cepa L.) field. Nitrous oxide fluxes were determined by a closed chamber method from the one-hundred 10- × 10-m plots. Physical (e.g., bulk density and water content), chemical (e.g., total N and pH), and biological (e.g., microbial biomass C and N) properties were determined from surface soil samples (0–0.1 m) of each plot. Geostatistical analysis was performed to examine spatial variability of both N₂O fluxes and soil properties. Multivariate analysis was also conducted to elucidate relationships between soil properties and observed fluxes. Nitrous oxide fluxes were highly variable (average 331 μg N m⁻² h⁻¹, CV 217%) and were log–normally distributed. Log-transformed N₂O fluxes had moderate spatial dependence with a range of >75 m. High N₂O fluxes were observed at sites with relatively low elevation. Multivariate analysis indicated that an organic matter factor and a pH factor of the principal component analysis were the main soil-related determining factors of log-transformed N₂O fluxes. By combining multivariate analysis with geostatistics, a map of predicted N₂O fluxes closely matched the spatial pattern of measured fluxes. The regression equation based on the soil properties explained 56% of the spatially structured variation of the log-transformed N₂O fluxes. Site-specific management to regulate organic matter content and water status of a soil could be a promising means of reducing N₂O emissions from agricultural fields.
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