64 



CROPS AS FEEDERS 



Crops requiring large amounts of potassium are usually rich 

 in protein or carbohydrates. 



Crops which require much calcium are rich in protein — alfalfa 

 is a good example. 



Crops Vary in Their Needs of Plant-food Elements. — Crops 

 vary in their requirements of the important elements. Cabbage, 

 sugar beets, tobacco, alfalfa and corn are some of the 

 ''heavy feeders.'' - \ , 



Fia. 25. — A soil actually gives up a part of itself in producing crops. 



nitrogen and mineral elements from the soil. 



All crops remove 



Wheat requires more nitrogen and phosphorus per bushel than 

 oats. It is interesting in this connection to mention that wheat 

 stands up much better on a comparatively rich soil than oats. 



It is better to grow such crops as potatoes, corn, sugar beets 

 or cabbage on land heavily manured or rich in nitrogen than to 

 attempt to grow oats. Under such conditions an oat crop lodges 

 badly. It is difficult to prevent lodging of grains on some soils. 



Lodging of Grains. — Lodging is explained on the theory that 

 the crops do not secure nitrogen and the mineral elements in the 

 proper proportion. A large amount of easily available nitrogen, 



