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Colloidal phosphate
consists of clay particles surrounded by
natural phosphate. Total phosphate is around
20% and "available" phosphate about 2-3%. An
efficient use of colloidal phosphate is to
add it directly to livestock manure in the
barn or lot, where the manure acids dissolve
much of the total phosphate and the
phosphate stabilizes the nitrogen in the
manure. Many of the same advantages can be
had by adding 20-50 pounds of colloidal
phosphate to one ton (two cubic yards) of
manure when composting. The ATTRA
publication
Farm-scale Composting Resource List
directs the reader to many useful resources
on composting. When direct land application
of rock phosphate is the only possibility,
spreading rates between 500 and 2,000 pounds
per acre are appropriate, depending on
phosphorus status, soil acidity, and
finances.
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