Effect of Fertilizer Management on Soil Carbon Dioxide Fluxes in Grassland and Cornfield during Winter

This study was conducted to investigate the effect of mineral (F) and Mineral-organic Fertilizers (MF) on soil CO2 flux during winter in grassland and cornfield in Southern Hokkaido, Japan, from May 2013 to April 2014. CO2 flux was measured by the static chamber method. Soil CO2 concentration was determined using silicone tubes pipe. The environmental variables, i.e. climate and soil, were also analyzed in this study. Results showed that, in freezing period, CO2 flux in MF was lower than F plots in grassland (0.1 and 0.4 Mg C ha^-1 period^-1, respectively). However, in melting period, CO2 flux in F was lower than MF plots (0.01 and 0.1 Mg C ha^-1 period^-1, respectively). CO2 flux in F and MF plot was similar in cornfield in freezing (0.5 Mg C ha^-1 period^-1) and melting (0.01 Mg C ha^-1 period^-1). These results were opposite to the annual CO2 flux where MF was higher than F plot in both grassland (10.9 and 8.5 Mg C ha^-1 period^-1, respectively) and cornfield (8.7 and 6.2 Mg C ha^-1 period^-1, respectively). Soil CO2 concentration during winter was relatively higher in grassland than cornfield. Soil NH4-N and Water Extractable Organic Carbon (WEOC) showed a positive correlation with soil CO2 concentration (r²= 0.39 and r²= 0.19, respectively). On the other hand, a negative correlation was observed between soil CO2 concentration and soil NO3-N content (r²= -0.39).