A popular science fair experiment is watering plants with carbonated water to discover if there is a benefit to the plant. The theory is that plants watered with carbonated water will grow faster than those watered with plain tap water due to the minerals and macronutrients in the carbonated water. Carbonated water contains phosphorous, potassium, sulfur and sodium, which are nutrients that plants need for healthy growth. A test performed by the University of Colorado at Boulder showed that plants watered with carbonated water grew faster and developed a darker green color.
Allow carbonated water to reach room temperature before using it to water plants. Plants can be shocked by using water at extreme temperature--either too cold or too hot.
Gently pour carbonated water into the plant's pot, holding the opening of the bottle close to the surface of the soil to avoid splashing (and creating a mess). Add enough water to thoroughly dampen the soil--generally, until water begins to drain from the bottom of the planter.
Water plants once a week with carbonated water to receive the maximum benefit. If plants become dry in the middle of the week, use plain water.