Section 1 Soil air 一、 Composition of soil air Compare soil air with atmosphere( Volume % Atmosphere O cO2 2 Other g ases Atmosphere 20.94 0.03 78050.95 near soil surface Soil air18.0-0.15-78.8 20.030.6580.24Section 1 Soil air 一 、Composition of soil air Atmosphere O2 CO2 N2 Other gases Atmosphere near soil surface 20.94 0.03 78.05 0.95 Soil air 18.0- 20.03 0.15- 0.65 78.8- 80.24 － Compare soil air with atmosphere（Volume %）