Gardening Articles: Edibles :: Herbs

No-Soil Gardening (page 2 of 5)

by Howard M. Resh

Light

For most hydroponic gardens, high-intensity discharge (HID) lamps provide the most effective and efficient supplemental lighting. The two main types of lamps are high-pressure sodium and metal halide.

These lights produce much more light per watt of electricity than fluorescent tubes, so the bulb can be several feet above the plants and still deliver sufficient light to the lower leaves. Both types of lamps use large, long-lived, and relatively expensive bulbs filled with various combinations of rare gases; the ballast is separate and plugs into a wall socket.

Most gardeners prefer metal halide lamps because their light is both good for healthy growth and flowering, and pleasing to work around. Sodium lamps are more efficient and are preferred for some flowering plants, but the lamps' reddish light is less comfortable to work around.

Water and Nutrients

Before transplanting into the hydroponic system, prepare the nutrient solution. While you can make up a solution from basic fertilizers, I recommend a ready-mixed formulation. This will simplify matters considerably, since you don't need to buy several different kinds of fertilizer or accurate weighing equipment.

While leafy vegetables require a different nutrient formulation from that used on tomatoes or cucumbers, you can use a general tomato formula if you are growing tomatoes with other vegetables. Hydroponic stores offer a wide range of formulations for various crops and even for different stages of growth.

The nutrient solution must be kept in balance, meaning that the ratio of nutrients must be constant. As the plants grow, they will take up the elements at differing rates, causing the solution to become out of balance. For this reason, it is best simply to change the solution every two weeks. Use the old solution to feed indoor and outdoor plants.

Besides keeping the nutrient ratios in balance, you also need to monitor the solution's pH and the amount of dissolved salts (the electrical conductivity or EC). Maintain pH between 5.9 and 6.3, and EC between 1.6 and 2.5 (EC will depend in part upon the nutrient formulation). Dealers offer a variety of products to measure and adjust pH and EC.

Add water regularly to the tank: plants consume water faster than nutrients. Keep the reservoir full most of the time, but you can allow it to fall three to four days before time to change it.

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