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Rock phosphate - Rx for poor soils.

The answer to what ails many soils in the Appalachian region may lie conveniently in a material that is mined in nearby North Carolina.

ARS soil scientists, Robert J. Wright and V.C. Baligar, have found that Carolina rock phosphate can partially ameliorate the acid soils that make it difficult to grow many crops in Appalachia. Acid soils are very common in the eastern United States.

Phosphorus is a major nutrient limitation to successful forage production, but many farmers can't afford the commercial fertilizer and lime additions generally recommended for pasture improvement.

Baligar, at Beckley, West Virginia, says commercial phosphorus is more expensive than rock phosphate because the raw rock has to be processed into a soluble form that roots can take in. But when the raw rock is applied to highly acid soils, the acidity causes the rock to dissolve.

Wright, formerly at Beckley and now at Beltsville, Maryland, says that within 30 days, dissolution of North Carolina rock phosphate in soil raises pH slightly and increases the availability of calcium and phosphorus to roots, while decreasing the toxicity of aluminum. The result is better root growth and improved water and nutrient use in infertile acid soils.

Ironically, North Carolina rock phosphate was once sold only overseas. In the past, Appalachian farmers tried other types of rock phosphate, without success, because it didn't dissolve fast enough to meet demands of growing crops - particularly corn and other row crops.

Wright and Baligar conducted laboratory tests and greenhouse experiments to determine the solubility and fertilizing effectiveness of North Carolina rock phosphate in acid soils common to Appalachia. They found that it was almost as effective as commercial fertilizer and also resulted in better root growth.

Field tests are being conducted in southern West Virginia to detemine the long-term effect of rock phosphate application on soil properties and the growth of grasses and legumes.

The tests should also determine if rock phosphate can reduce the need to lime Appalachian pastures.
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Author:Comis, Don
Publication:Agricultural Research
Date:Feb 1, 1993
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