- Tomatoes and other plants depend on two gases for survival. Leaves take in carbon dioxide for use in photosynthesis, but roots absorb oxygen from the soil. Anaerobic conditions in the soil, including flooding, suffocate the plants. Tomatoes in well-drained soil find moisture and air in the damp earth. Soil also contains major nutrients such as potassium, nitrogen and phosphorus as well as minor nutrients such as iron, copper and boron. Ordinary water lacks nutrients in enough quantities to sustain tomato plants. In hydroponic farming growers replace soil with artificial physical support for the plant and a nutrient-bearing flow of water. Fertilizer and oxygen dissolved in the water supply the plant's basic needs.
- Tomatoes depend on soil for physical support as well as nutrition. In hydroponics farming, artificial growing media like rock wool replace the physical structure of soil. In some systems, roots grow completely immersed in flowing water but depend on floats or platforms to keep the upper tomato plant stable. Tomatoes absorb nutrients well only within a particular range of pH, a measure of the soil's alkalinity or acidity. Hydroponics systems adjust the water's pH to between 5.0 and 7.0 to prevent plants from poisoning themselves with too much of some elements or starving by drawing up too little of others.
- Tomato plants depend on at least 16 different nutrients found in soil. Natural water flows like floods play an important part in recharging soil with nutrients such as nitrogen, phosphorous and potassium. Rock particles in the soil provide other trace minerals such as boron, zinc and molybdenum. To use water as the nutrient-bearing part of the growing system, hydroponics farmers add these critical mineral salts to aerated oxygen-rich water in precise amounts. As plants use nutrients, the fertilizing water cycles out, and fresh water with a perfect nutrient balance replaces it.
- Homeowners with limited space or without tillable land could still grow tomatoes and other vegetables using a small-scale version of soil-less farming. Commercial growers depend on deep-water tank systems too large and expensive for most home gardeners. Aeroponics systems allow vegetable production in small spaces by replacing both soil and water tanks with better technology. In an aeroponics system, plants start in peat or rock wool inserts in a frame over a closed chamber. Roots dangle in the air-filled chamber, and an automatic irrigation nozzle sprays the roots with fertilizer solution as needed. Water still conveys nutrients to the plants, but the system uses much less water and energy than conventional hydroponics tanks. Advanced soil-less farming methods including aeroponics could produce crops worth $50,000 yearly on only 1/2 acre, notes "Wired" magazine.
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