Rhizobia-heterotrophic aerobic type Plants provide organic matter, so the C source is sugar and the N source is nitrogen in the air. Nitrifying bacteria-autotrophic aerobic type. Because autotrophs can only use inorganic substances to synthesize the required organic substances, they use inorganic C source 2 to oxidize carbon, and N source is mainly 1 ammonium salt and nitrate. Denitrifying bacteria-heterotrophic anaerobic type. C source is sugar, and inorganic nitrogen source and organic nitrogen source can be used, wherein inorganic nitrogen source is ammonium salt and nitrate, and organic nitrogen source is peptone, beef sauce, etc.