184 SYSTEMS OF PERMANENT AGRICULTURE 



Third are the extensive deposits of phosphatic iron ores con- 

 taining more or less ferric phosphate, FePO 4 , the phosphorus being 

 recovered in the slag produced in the conversion of pig iron into 

 steel. 



About three fourths of the phosphorus taken from the soil by 

 crops of corn, wheat, or other cereals, is deposited in the grain or 

 seed, about one fourth remaining in the straw or stalks. If the 

 grain is sold, three fourths of the phosphorus required for the crop 

 is sold with it; and, likewise, when grain is bought and brought to 

 the farm, a like proportion of phosphorus is brought with it. 



When crops are fed to animals, as a general average about 

 three fourths of the phosphorus, three fourths of the nitrogen, 

 and practically all of the potassium are returned in the manurial 

 excrements. Thus, if sufficient grain is bought and fed, and if the 

 manure is saved and applied to the land, the soil can be made richer 

 in phosphorus year by year, and in most sections some instances 

 can be found of farmers who succeed in maintaining or increasing 

 the fertility of their soil by this practice. If they have the neces- 

 sary knowledge and skill and material equipment and sufficient 

 capital, they may feed stock for the open market, or if this is not 

 profitable, they may produce pure-bred stock to sell at higher prices 

 for breeding purposes. In any case, live-stock farming can never 

 be permanently profitable to a large proportion of the farmers 

 in a great agricultural country, because the world cannot live on 

 meat and dairy products only, and the relative supply and demand 

 always compels the sale of much grain from most farms. Conse- 

 quently, this system of adding phosphorus to one farm by taking 

 it from other farms must be of limited application; and live-stock 

 farmers who feed only the produce from their own land gradually 

 reduce the phosphorus of the soil at least by the amount sold in 

 the animal products. 



A still more limited supply of phosphorus is secured for use in 

 soil improvement by utilizing the bone meal prepared by the pack- 

 ing houses. This, of course, also comes from the soil originally. 

 It is made chiefly from bone scraps which have no value for other 

 uses. The best bone is worth several times as much for the manu- 

 facture of buttons, cutlery, toilet articles, etc., as for fertilizer 

 purposes. Probably not more than one tenth of all the phos- 



