(54 DRY FARMING 



legume system and 25.2 bushels in the fallow system. In 

 this same rotation wheat produced 25.0 and 27.1 bushels 

 respectively. 



In another field (Broadbalk Field) wheat has been 

 grown continuously for 55 years unfertilized, the aver- 

 age yield being 12.9 bushels. In still another field (Hoos 

 Field), barley has been grown continuously for 55 years, 

 unfertilized, the average yield beeing 14.8 bushels. This 

 is positive proof of the benefit of crop rotation over a 

 one-crop system. It was pointed out, however, from 

 table XIII., that crop rotation without fertilization 

 would not maintain the crop yields. The matter of crop 

 rotations is discussed fully elsewhere and it is intended 

 here only to emphasize the fact that whereas a rotation 

 is much superior to a one-crop system, provision should 

 be made in the rotation for the return of organic mat- 

 ter and nitrogen and the mineral plant-food elements, 

 especially phosphorus, if deficient. Crop rotation with 

 no return of plant food is only a more efficient way of 

 robbing the soil; it makes possible greater crops, which 

 means the withdrawal of greater amounts of plant food 

 and therefore more rapid depletion of the soil's fertility. 



THE SOIL A LIVING MASS. 



44. Importance of Microorganisms in the Soil. We 

 have seen that animals are dependent upon the higher 

 plants. In turn the higher plants are dependent upon 

 microorganisms. If the action of the latter were stop- 

 ped for any considerable length of time, life would be- 

 come impossible upon the earth; our very existence de- 

 pends upon them. 



The question might well be asked: What would be 

 the condition of the earth, if, through the many ages, the 



