Page:Popular Science Monthly Volume 84.djvu/62

58 be lost by leaching than is added in the rain and by the azotobacter and other non-symbiotic bacteria.

While these systems are distinctly for live-stock farming or for grain and hay farming, they should be considered as only suggesting the basis for solving the nitrogen problem. In diversified farming a combination of these systems will often be preferred to either one alone. The important point is that the landowner should know the essential facts and base his practise upon them in order to provide for permanent fertility with respect to nitrogen, phosphorus and limestone.

Louisiana Experiments.—The longest record of a rational permanent system of agriculture conducted in America is furnished by the Louisiana Experiment Station. As an average of nineteen years, the values per acre of three crops were $29.79 from unfertilized land, and $92.04 where organic manures and phosphorus were regularly applied in a three-year rotation of (1) cotton, (2) corn and cowpeas, (3) oats and cowpeas. Here the crop values from the well-fertilized land average more than three times as great as those from the unfertilized land under the same rotation and with two legume cover crops grown every three years.

Ohio Experiments.—The Ohio Experiment Station has reported sixteen years' results from a three-year rotation of corn, wheat and clover, both from unfertilized land and from land treated with farm manure and phosphorus. As a general average, the values per acre of the three crops at conservative prices were $27.07 on untreated land, $44.65 where farm manure was applied, $53.82 where manure and rock phosphate were used, and $53.61 where manure and acid phosphate were applied, practically the same yields having been secured whether the phosphorus was applied in raw rock phosphate or in acid phosphate, costing twice as much. The well-fertilized land has produced nearly twice as much as the land where no manure and phosphate were used, although clover was grown every third year in the rotation and all of the land was limed.

On the basis of these figures, 8 tons of manure were worth $17.58, or $2.20 per ton; and the rock phosphate, costing about $7.50 or $8 per ton, was worth $57.31; or, if we use the Ohio methods of computing the amount and value of the increase produced, each ton of raw phosphate was worth $65.63; and it may well be added that to obtain the same amount of phosphorus in the common high-priced mixed manufactured commercial fertilizer, such as farmers are advised by the