242 MISSOURI AGRICULTURAL REPORT. 



ed, assuming that none would be wasted and that the wheat could extract 

 al! of the nitrogen from the soil. Neither of these assumptions is true, 

 however, but we assume them to be true for the purpose of making com- 

 parisons. This soil would produce corn at the rate of 50 bushels per acre 

 about half as long as it would produce wheat. 



The richest soil found in our table contains about 27,000 pounds of 

 nitrogen per acre in the first four feet. This would supply nitrogen for 

 maximum crops of wheat 575 years and for maximum crops of corn 279 

 years. The average of the 49 soils analyzed contained nitrogen sufficient 

 for 213 maximum crops of wheat and for 103 maximum crops of corn. 

 The average of three Missouri soils selected from the table contains about 

 the same amount of nitrogen as was found in the average of the 49 soils 

 just given. 



Comparing with respect to phosphoric acid we find that the poorest 

 soil contained enough to produce maximum crops of wheat 60 years and 

 m.aximum crops of corn 21 years. The richest soil would produce max- 

 imum crops of wheat 4659 years and maximum crops of corn 1635 years. 

 The average of the 49 soils would produce wheat 633 years and corn 

 226 years. . The average of the three Missouri soils would produce max- 

 imum crops of wheat 221 years and maximum crops of corn 81 years 

 before all the phosphoric acid found within the reach of these plants 

 would be exhausted. 



Comparing in the same way with respect to potash, the poorest of the 

 49 soils contained enough of this element for 44 maximum crops of wheat 

 and only 15 maximum crops of corn. The richest one would produce 

 wheat over 9000 years and corn over 3000 years. The average would 

 produce wheat 2500 years and corn nearly 1000 years. Tlie average of 

 the three Missouri soils would produce 25 bushels of wheat per acre 6000 

 years and 50 bushels of corn per acre 2100 years before the potash found 

 within reach of the roots of these plants would be exhausted. 



A recapitulation of the figures just presented will emphasize the fol- 

 lowing conclusions drawn from them : That some soils have been found 

 in which some of the elements under discussion is practically exhausted. 

 That in average soils the nitrogen will become exhausted by cropping 

 much more quickly than the other elements. That in average soils all 

 these elements exist in greater abundance than the average yield of crops 

 would lead one to suppose. We must remember, however, that the chem- 

 ist by his methods might be able to find large quantities of these elements 

 present and yet they might be locked up in some form wholly unavailable 

 to plants. The average soils of the United States have been under culti- 

 vation less than 100 years and yet our annual bill for fertilizers is now 

 $60,000,000. Evidently farms do become poor with respect to crop pro- 



