Vast mountains of discarded auto tires in the United States and Mexico are turning up, in altered form, to improve grape production in Italy, orange harvests in Spain, and fresh vegetable production in Saudi Arabia. Soon they may help apple growers in Australia and improve the turf in Sydney's parks, just as they are helping orchardists, truck farmers, and park superintendents in this country. The tires are being turned into an irrigation aid -- a soaker hose that happens to be one of the more inexpensive, effective, easily laid, durable, and trouble-free of the ``drip irrigation'' systems available. For several years Hydro-Grow hose, as it is termed, was available only to farmers, but recently it has come on the market in home-garden quantities through Gardener's Supply Company in Winooski, Vt.
Paradoxically, Hydro-Grow hose is the direct result of the failure of an earlier product being developed. Eight years ago, Dr. Art Cervera and other scientists with the Hydra-Chem International Corporation of Dallas were looking for ways to recycle used auto tires by developing products that could be made from the reclaimed rubber. A conventional garden hose appeared logical, but from the start getting a totally leak-proof hose from the recycled rubber appeared impossible, at least if it was to remain inexpensive. Then someone realized that if the naturally porous product could be made to leak uniformly throughout, it would make an ideal soaker hose. It has.
Hydro-Grow's one-eighth-inch-diameter wall will withstand 100 pounds of water pressure and can be buried without collapsing under the weight of the surrounding soil. Tests show that it cannot be cut or punctured by any ``conventional garden tool'' -- meaning spade, fork, or trowel. This same sturdiness has one disadvantage, however: It cannot turn on a dime, so to speak, but requires an 18- to 20-inch radius at bends.
So far, the hose's major application in the United States has been under turf, where, at 2 to 4 inches below the surface, it draws down the grass roots, largely eliminating thatch caused by excessive root growth at the surface.
In orchards, vineyards, or any other perennial plantings, it is recommended that the hose be permanently buried. In annual flower and vegetable gardens it can be laid on the surface and covered with a mulch. The hose is laid 3 feet on center in either buried or surface applications.
While it will withstand heavy water pressure, the Hydro-Grow hose works most effectively between 6 and 10 pounds of pressure (typically a one-eighth to one-quarter turn of an outdoor tap) and will work on pressure as low as 3 pounds per square inch.
Soaker hoses or drip irrigation tubes offer two great advantages to the gardener or farmer: They make irrigating a snap -- even being automatic, with the help of an inexpensive timer -- and they make a little water go a long way. Typically there is a 30 percent saving in water used, and often this figure can go as high as 50 percent. Little water is lost to evaporation (none at all if the hose is underground or beneath a mulch), to runoff, or to leaching, because it is applied slowly over a long period only where it is needed -- at the root zone. For similar reasons liquid fertilizers are also applied more efficiently this way.
While more efficient water use is always advisable, it appears particularly important right now after an overly dry fall, winter, and spring over much of the country. Reportedly conditions are the worst in 20 years east of the Appalachians,which suggests that widespread water restrictions will be imposed later this season.
Efficient water use, even if your irrigation system is just a hand-held watering can, also involves mulching with leaves, straw, hay, newspaper, corrugated cardboard, or even old carpeting. Not only does a mulch slow down water loss by evaporation, it helps relieve stress in a plant by moderating soil temperatures. The fact that earthworms remain active right up to the surface of the soil is another plus. Plastic mulches are also good moisture savers, but unless applied over an organic mulch they will boost soil temperatures.
Hydra-Chem International Corporation (PO Box 802104, Dallas, Texas 75380) is considering licensing the manufacture of its product both overseas and to others in the US. Home garden quantities are available from Gardener's Supply Company, 133 Elm Street, Winooski, Vt. 05404.