But this progressive, practical farmer is only putting into profitable practice the results of the long-continued careful investigations with raw phosphate conducted by such public-service institutions as the agricultural experiment stations of Pennsylvania, Maryland, Rhode Island, Massachusetts, Ohio and Illinois. He knows also that on four different fields of typical Corn-Belt land in McLean county, Illinois, the total crop values per acre for a period of ten years were $148.75 $151-30, $149.43 and $149.96, respectively, and that on four other adjoining or intervening fields, which differed only by two liberal additions of phosphorus during the ten years, the respective crop values for the same time were $229,37, $221.30, $229.20 and $225.57. Of course, Mr. Mann does not buy nitrogen, but he takes it from the inexhaustible supply in the air by means of clover and alfalfa or other legumes. He does not buy potassium because he knows how to liberate it from the inexhaustible supply contained in the soil, and because he knows that in the Illinois investigation just cited the crop values from four different fields not receiving potassium were $148.75, $151.30, $229.37 and $221.30; while four other adjoining fields, which differed only by liberal applications of potassium, produced during the same ten years $149.43, $149.96, $229.20 and $225.57, respectively. Thus, as a general average, phosphorus increased the crop values by $76.50 an acre, which amounts to more than 300 per cent on the investment, and at the end of the ten years the soil on the best treated and highest yielding land was 10 per cent richer in phosphorus than at the beginning; while the crops from the unfertilized land removed an amount of phosphorus equal to nearly one-tenth of the total supply in the plowed soil. But a similar general average shows that potassium produced increased crop values worth only 86 cents, or 3 per cent of its cost. What other results should be expected from land containing in the plowed soil of an acre less than 1200 pounds of phosphorus and more than 36,000 pounds of potassium? "Working" the Land If there is one agricultural fact that needs to be impressed upon the American people it is that the farmers of this country have been living, not upon the interest from their investments, but upon their principal; and whatever measure of apparent prosperity they have had has been taken from their capital stock. The boastful statement sometimes made, that the American landowner has become a scientific farmer, is as erroneous as it is optimistic. Such statements are based upon a few selected examples or rare illustrations, and not upon any adequate knowledge of general farm practice. Even to this date almost every effort put forth by the mass of American farmers has resulted in decreasing the fertility of the soil.