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Show Gravel May Turn Barren Land Into Producing Oasis Ordinary gravel may be used one day to transform barren prairies into crop-producing crop-producing land. RECENT TESTS by the USDA's Agricultural Research Service show that a mulch of gravel on bare soil increases crop yields by reducing soil water evaporation evapora-tion and increasing soil-temperatures. soil-temperatures. Agricultural scientists believe the gravel mulch can be a boon to food production if practical methods can be developed for its use. THE MULCH may enable crop production in semi-arid lands that are now uncultivated, uncul-tivated, and may help stabilize crop yields in drylands where irrigation water is scarce. An estimated 25-50 percent of applied irrigation water normally 'Vaporates from the soil before it can be used by crops. Use of the mulch would reduce the evaporation rate and make more water available availa-ble to growing plants. IN LAB and field tests at Fort Collins, Colo., a gravel mulch about l'2 inches thick was placed on the soil surface between crop rows. Test results were compared with those from a normal bare soil surface, ' The gravel acted as a oneway valve. Its large pores allowed water to infiltrate the soil rapidly, and created irregular pressure areas that slowed the escape of water vapors back to the atmosphere. at-mosphere. SOIL TEMPERATURES six inches under the mulch were two to four degrees higher than that under bare soil. This allowed seedlings to germinate and emerge two to three days earlier. By the time the plants were large enough to shade the soil, temperatures for both treated and untreated soil were similar. THE STUDIES showed that two management practices will be required in using gravel as a mulch. Since it reflects sunlight, the gravel would have to be alternated with 4-inch bare rows to prevent plant damage. The mulch a; so would have to be lifted and placed on top of the soil each year so that it wouldn't become mixed with dirt and lose its water-conserving effectiveness. ONE GRAVEL - extracting, soil-sifting machine already has been developed by a University of Arizona engineer en-gineer and is undergoing test. It reportedly shows good potential po-tential for establishing a mulch from naturally occurring occur-ring gravel in the soil's top four to six inches, and for regenerating an established mulch. Scientists say additional research will be conducted on the gravel mulch in various climates. |