The invention is related to agriculture, in particular to the setup of greenhouse centers for cultivating vegetables and flowers, for example, in raised beds, but it can also be used for cultivating plants on open land. The claimed method involves the dissolution (in saturator 1) of CO2 from compressed air in water with formation of chemical bonds, and then the resulting volume of nutrient solution from saturator 1 is used for watering the plants (in particular, through a watering-and-feeding irrigation system). The purified carbon dioxide gas is extracted from atmospheric air by pumping it into saturator 1 with the help of, for instance, compressor 3. The volume of saturator 1 is first (before the air is pumped in) is filled with water so that an air pocket - cavity 6 - can form. The air is then pumped into saturator 1 until the pressure in cavity 6 exceeds atmospheric pressure. After that, using pressure relief valve 8, air depleted of CO2 by partial dissolution in water is emitted from the aforesaid cavity 6 into the atmosphere while compressed air from compressor 3 is pumped through at the same time. Thus the air pressure created previously in cavity 6 is maintained until a nutrient solution with the necessary concentration of dissolved carbon dioxide gas is obtained. The optimum air pressure to be maintained in cavity 6 of saturator 1 is preferably within the range of 5 to 10 atmospheres. It is practical to supply the air into saturator 1 through the bottom part of saturator 1 under pressure sufficient to force it into air cavity 6 of saturator 1 through the volume of the water column. To produce the nutrient solution, it is advisable to use water that is free of contaminants, preferably distilled or filtered through a membrane by reverse osmosis. As a rule, the saturators volume is pre-filled with water chilled to a temperature below ambient. 1 independent claim and 4 subclaims, 1 illustration
