A method is described for treating soil to increase plant growth or improve the health of plants, wherein a combination of carbon dioxide and a surfactant having pesticidal effects is applied. The invention also pertains to methods for applying bio-derived surfactants in combination with carbon dioxide to crops and other plants or to the soil used for such plants in order to reduce the need to apply environmentally unfriendly pesticides or fertilizers, as well as to improved methods of removing carbon dioxide from the atmosphere by applying the carbon dioxide to plants and soil in combination with surfactants, particularly bio-derived surfactants that can reduce the activity of certain pests in the soil.