Tillage Reversal and N Fertilization Effects On Diurnal CO2 Emission On a Black Chernozem and a Gray Luvisol.

Diurnal variability in the rate of emission of carbon dioxide (CO₂) from Black Chernozem and Gray Luvisol were studied by using a chamber technique to measure the CO₂ emission rates at sites on fertilized and unfertilized (N), tilled and tillage reversed soils at 2-h intervals from 6am to 10pm in July and August, 2013. The soil CO₂ efflux ranged from 100 to 400 mg C m^-2 h^-1 during the measurement period. The maximum soil CO₂ efflux occurred around 14:00 for all treatments on both sites. The diurnal variability of CO₂ in July was larger than that in August. It is perhaps due to the crop growth which needs further study. N application inhibited CO₂ emission in Black Chernozem (p<0.05) while enhanced CO₂ emission in Gray Luvisol (p<0.05) according to data collected in July. N combined with tillage reversal diminished N effect on CO₂ emission in August. Tillage reversal had no significant influence on CO₂ emission based on the diurnal CO₂ flux measurement. Overall our results indicate that N application may not necessarily enhanced diurnal CO₂ emission, which depend on soil type and if combined with tillage.