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Phosphorus In SoilBone Meal: This is possibly the most overrated of all fertilizer materials. Beloved by tradition-bound British gardeners, it has been the universal remedy recommended whenever the "authority" was stumped and had to say something. I suspect the reason bone meal is so frequently recommended is that since it does nothing to the plant of any importance, it does no harm. In fairly acid soils, for example those with pH readings of from 5.8 to 6.2, phosphorus becomes available if bone meal is used liberally. In soils of higher or lower pH readings, phosphorus locks up in insoluble forms that cannot be used by plants. Where phosphorus is needed, superphosphate will supply it at a fraction of the cost of bone meal, and in much more available form. If bone meal can be had practically for nothing it has some slight value, largely for its small content of nitrogen. Rock Phosphate: In raw form, just as it is dug from the ground and pulverized, rock phosphate is a fairly good source of slowly available phosphorus. The studious gardener who consults foreign texts should not be deceived, however, by results reported in Europe. Phosphate rock used abroad comes from Africa and is of a different type than American rock. The African product provides much more available phosphorus. Finely ground American phosphate rock, in acid soils, becomes slowly available after the second year. In alkaline soils, it is practically worthless. Superphosphate: This is the basic phosphorus fertilizer. It is a mixture of monocalcium phosphate and calcium sul ate, produced by treating the raw rock with sulfuric acid. The regular grade contains about 20 per cent phosphoric acid, while triple super phosphate may go as high as 48 per cent. Someone has said that without this source of phosphorus, American agriculture would grind to a halt. While this is a bit extravagant, the statement does point up the vital role played by this one material. Chemical Nitrogen In Soil
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