A good potting mix must be loose enough to let the roots develop freely. It must provide enough air space (despite container compacting) to allow good air and water circulation; it must have the right pH balance; and it must retain nutrients and water yet still drain well.
To fulfill these requirements, most potting mixes are a good combination of organic matter and minerals. The organic component may be peat moss, compost, bark, redwood sawdust, shavings, or any combination of these. The mineral element may be vermiculite, perlite, pumice, builder's sand, or a combination of ingredients.
Garden stores everywhere sell synthetic soil' or soiless mixes' under various trade names: Redi-Earth, Jiffy Mix, Metro Mix, Super Soil, Pro Mix, and many others. Most also contain a balance of nutrients. The exact formula may vary depending on what you intend to grow.
Jiffy Mix, for instance, is composed of equal parts of shredded sphagnum, peat moss and fine grade vermiculite plus just enough nutrients to sustain initial plant growth.
A tomato formula contains a balance of fast- and slow-release nutrients formulated for tomatoes plus sphagnum moss, vermiculite and solid soil matter.
Two of the most popular mixes were perfected at Cornell University and at the University of California. The California formula is available under the names First Step and Super Soil.
If you'd rather make your own potting mix here's the formula for the Cornell mix.
Vermiculite Shredded peat moss Superphosphate Limestone
Dried cow manure or steamed bone meal
8 quarts 8 quarts
Measure and place all ingredients in a garbage can liner. Shake vigorously. Since the Cornell mix has no smell, you can place it in plastic bags and store it in the back of a closet
Although it is possible to grow vegetables in one of these potting mixes, they generally do better in a combination of soil, potting mix and other ingredients. Vegetables in soil mixes require less frequent feeding than those in potting mixes. Furthermore, a combination soil-potting mix holds water better.
Ail-Purpose Vegetable Soil Mix: One part each of:
Commercial potting mix
Compost (homemade or purchased) or vermiculite Common garden soil.
Purchased soil is already sterilized. Soil from the ground is not, and you might want to sterilize it to destroy weed seed and nematodes and to avoid passing on fungus and disease.
You can sterilize your soil be spreading it out in a shallow pan and baking it at 275° F for an hour. To overcome the odor problem, soak the soil thoroughly before putting in the oven. (It should be noted that some gardeners prefer to take their chances with disease. They will not bake soil because it destroys all the microorganisms, thus making the soil dead.' The compost, of course, brings it back to life.)
WATERING TECHNIQUES ~
There are a number of ways to water containers. In general, pots less than eight inches in diameter should be watered from above. The entire container can also be half submerged in a pail of water. When the bubbles stop rising, take the container out and let it drain.
Water larger containers from above with a watering can or a hose; there are a number of specialized types of watering cans on the market To keep the stream of water from a hose from hurting your plants, use a gentle stream or one of the water-breaking nozzles. (See Chapter 7 for complete information on watering.]
Water all vegetables until the soil is completely saturated. Don't water again until the soil is dry to a depth of 1 or 2 inches. To check, poke a finger an inch or two into the earth, take some soil from this depth and rub it between thumb and index finger. If the soil is dry to your touch, it's time to water. If the soil is mud-coated or feels wet, don't water for at least another four hours.
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