cent, of potash on the first foot of ground. A crop of wheat removes 

 about fifteen pounds of potash from each acre. It has been estimated 

 that the first eight inches of soil contain on an average enough nitrogen 

 to last ninety years, enough phosphoric acid to last five hundred years, 

 and enough potash to last one thousand years. This supply is mate- 

 rially increased when we consider the great depth penetrated by the 

 roots of wheat." 



Practically all agricultural soils of the United States contain an inex- 

 haustible supply of all of the inorganic elements mentioned, except 

 phosphorus and lime, and, possibly, potash. 



We know that these inorganic elements are in the disintegrated par- 

 ticles of rock and that they are found not only in the surface soils, but in 

 all soils below the surface. 



It is also known that by growing deep-rooting plants such as the 

 alfalfa, clover and many others, dormant plant food far below the reach 

 of the plow can be made available and utilized by being brought to the 

 plant roots in a soluble state by capillary attraction. 



Manures 



We also know that one-quarter of the nitrogen and nearly all of the 

 phosphoric acid and potash which enter into a crop of wheat are con- 

 tained in bran screenings and middlings, and that fully eighty per cent 

 can be returned to the soil if they are fed to live-stock and the manure is 

 placed on the ground. Barnyard manure is an ideal fertilizer for wheat. 

 It furnishes all of the plant food elements which enter into the crop 

 besides organic matter which is the main substance in maintaining nitro- 

 gen and soil bacteria. It also places the soil in a good physical condi- 

 tion, making it mellow and permeable. In sections where manure 

 cannot be secured, the organic matter can be provided by plowing 

 under green crops and the inorganic plant food elements such as potash, 

 phosphorus, etc., can be supplied in a commercial form. 



Lawes and Gilbert give the results of their experiments with wheat as 

 follows: 



"No manure for forty years, averaged 14 bushels; farm yard manure 

 for thirty-two years, averaged 32 1 bushels." 



Rothamstead average of eight favorable harvests: 



Farm Yard Manure 

 No Manure 



Weight, 

 Per Bushel 



62 . 6 pounds 

 60 . 5 pounds 



Grain, 

 Per Acre 



2342 pounds 

 1156 pounds 



Straw, 

 Per Acre 



6089 pounds 

 2872 pounds 



