No. 4.] KEEPING UP FERTILITY. 95 



our crops. It was a commendable effort to adapt the food 

 to the appetite of the plant. In so far as the system is 

 based on the composition of the crop to be produced, it can- 

 not be regarded as wholly scientific. The soil as well as the 

 crop should be considered. The soil contributes to the food 

 of the plant, and soils naturally vary. The peculiarities of 

 the crop should also be taken into account. Plants differ 

 widely in their ability to forage for themselves. Some are 

 like Devon or Ayrshire cows, — able to fatten on scanty 

 pasturage ; others are like Shorthorns, who require abun- 

 dance of rich feed at hand. Thus the potato, for example, 

 is a poor feeder. Indian corn is a far better forager. The 

 season during which the plant makes its chief growth also 

 affects the necessity of supplying the different elements of 

 food, particularly the nitrogen. The grass crop, for example, 

 does not withdraw from the soil an exceptionally large sup- 

 ply of nitrogen. In four tons of English hay there are 113 

 pounds ; in 100 bushels of corn and three tons of stover 

 there are 163 pounds ; yet for the grass it is best to apply 

 considerable nitrogen in available form in early spring, while 

 for corn a large application of available nitrogen is not gen- 

 erally required. 



