Cyril G. Hopkins, "Shall We Use 'Complete' Commercial Fertilizers in the Corn Belt?" (1912)

“The real question is, shall the farmer pay ten times as much as he ought to pay for food to enrich his soil? Shall be buy nitrogen at 45 to 50 cents a pound when the air above every acre contains 70 millions pounds of free nitrogen? Shall he buy potassium at 5 to 20 cents a pound and apply 4 pounds per acre when his plowed soil already contains 30,000 pounds of potassium per acre, with still larger quantities in the subsoil? Because his soil needs phosphorous, shall he employ the fertilizer factory to make it soluble and then buy it at 12 to 30 cents a pound in an acid phosphate or “complete” fertilizer when he can get it for 3 cents a pound in the fineground natural rock phosphate, and when, by growing and plowing under plenty of clover (either directly or in manure), he can get nitrogen with profit from the air, liberate the potassium from the inexhaustible supply in the soil, and make soluble the phosphorous in the natural rock phosphate which he can apply in abundance at low cost?”
                                  - Cyril Hopkins, Chief Agronomist and eventual Director of the Illinois Agricultural Experiment Station from 1911 to 1919

        Prices may have changed, but the basic truths about long-term soil fertility and economic independence for the farmer are as clear now as they were then.
        The efforts of Cyril Hopkins serve as a metaphor for independent truths set up against an advertising and sales blitz that tries to pretend the truths don’t exist. The result of more than a half a century of fertilizer salesmanship is that no one today remembers Cyril Hopkins. The soil fertility truths that he championed, although they were understood for generations, have been forgotten so long that they are now regarded as some sort of revolutionary heresay.
         Hopkins was well aware of that possibility. He wrote numerous experiment station bulletins encouraging farmers to realize that no salesman was going to tell them about these ideas because there was so little to sell. He warned them that the large fertilizer manufacturers were concerned first and foremost with selling and only secondarily with farming. He predicted that the manufacturers would push their products endlessly, until farmers forgot how well agriculture could work with a bare minimum of purchased products. Well, Cyril Hopkins may have lost that struggle and been momentarily forgotten, but the truth of “permanent soil fertility” is still right there in the earth for those who care to look.
                                - Eliot Coleman