More Bushels and Tons

The Ohio Agricultural Experiment Station has reported investigations covering sixteen years in which raw phosphate was compared with acid phosphate costing twice as much per acre.  As an average of all results secured, 320 pounds of raw phosphate applied with manure on clover sod produced 8.4 bushels more corn, 4.7 bushels more wheat, and 0.49 ton more hay per acre than where manure alone was used, and 320 pounds of acid phosphate, costing twice as much money but containing only half as much phosphorus, applied with the same amount of manure, produced 7.5 bushels more corn, 5.1 bushels more wheat, and 0.46 ton more hay than where the manure alone was used.

Now I have presented the averages or summaries of all investigations that have been reported covering ten years or more where equal money values of raw phosphate and acid phosphate have been used, or where any apparent provision was made to supply some organic manure, whether as farm manure, green manure or merely as clover grown in the rotation; and I invite the reader to mix his own brains with these data and not to expect me to state whether he should use the relatively cheap ground natural phosphate rock or the more costly manufactured acidulated phosphate in the improvement of his own soil in systems of permanent profitable agriculture.

Making Phosphate Available

If the natural rock is used it should be ground so that at least 90 per cent will pass through a sieve with 10,000 meshes to the square inch, and of course its content of phosphorus (from 12 to 15 per cent) or of so-called “phosphoric acid” (from 27 to 34 per cent) should also be guaranteed.  Moreover it should be used liberally and in connection with plenty of decaying organic matter.  People sometimes ask, “How much of the phosphorus in raw phosphate is available?” The best answer to this question is, “None of it; and, if you are not going to make it available, don’t use it.”

On my own farm I use about one ton per acre of raw phosphate once every six years, thus adding at least 250 pounds of phosphorus at a cost of less than $8; whereas 200 pounds of the common “complete” fertilizer per acre yearly would cost $12 every six years, and would supply only 40 pounds of phosphorus.  I do not use “complete” fertilizers, because there is plenty of nitrogen in the air and plenty of potassium in the soil; and because, by growing and plowing under plenty of clover, I not only secure nitrogen from the air and liberate potassium from the soil but also liberate the phosphorus from the raw rock phosphate applied to the soil.  In beginning the use of raw phosphate where the supply of organic manures is limited, I apply one ton of phosphate and 600 pounds of kainit in intimate connection, turn them under, preferably with organic matter, then add ground limestone if needed, and thus prepare to grow clover.