Table 1 Variation of soil CO2 concentrations (mL L-1) averaged for with soil depth (SD) at the jointing, heading, and filling stages of wheat growth period under the fertilization levels of 75% (75% NF), 100% (NF) and 125% (125% NF) of the normal fertilizer application rate and the groundwater depths (GD) of 20, 40, 50, 60, and 80 cm. The values shown are the means of three replicates ± standard deviations. Within a treatment, the means followed by different lowercase letters are significantly different atP ≤ 0.05 as determined by the LSD test