104 



SOILS AND FERTILIZERS 



When legumes are grown and the crops removed from 

 the land, some means should be taken to replace the 

 phosphorus and potassium taken from the soil. 



The average yield of wheat on an acre in the United 

 States is about 15 bushels, or 900 pounds, while the 

 yield of oats is 30 bushels, or 960 pounds, an acre. 



900 Lbs, WHEAT 



960 Lbs, OATS 



FIG. 40. Showing the Plant Food taken from Soil by Wheat and by Oats. 



It will be noticed that there is very little difference 

 in the decrease caused by these two grains. The fact 

 that virgin soil that is well supplied with plant food will 

 produce from 30 to 50 bushels of wheat an acre and that 

 the average yields in this country are less than half 

 the maximum yields shows the results of constant 

 cropping without proper fertilization. Some of the 

 European countries are now producing from 30 to 50 

 bushels of wheat an acre by adding fertilizers. 



About 30 bushels of corn are raised on an acre in this 

 country. This crop, it will be observed, removes more 

 fertility than either wheat or oats. The frequent 



