CONSERVATION OF FERTILITY 243 



section 133. This would make the total loss of nit- 

 rogen over 28,500 pounds or 177 pounds per acre, 

 which large as it may seem is the actual loss from 

 the soil when grain only is raised and is sold. Ex- 

 periments at the Minnesota Experiment Station 

 showed that after a soil had been cultivated 40 years, 

 the annual loss per acre of nitrogen in exclusive 

 wheat raising was 25 pounds through the crop and 

 146 pounds due to the oxidation of the nitrogenous 

 humus of the soil. 18 



EXCLUSIVE GRAIN FARMING. 

 Sold from the Farm. 



Phosphoric 



Nitrogen. acid. Potash. 



^ Pounds. Pounds. Pounds. 



Flax, 40 acres 1600 600 800 



Flax straw 600 120 320 



Wheat, 50 acres 1250 625 350 



Wheat straw 500 375 1400 



Oats, 20 acres 700 240 200 



Oat straw 300 1 20 700 



Barley, 50 acres 1400 750 400 



Barley straw 600 250 1500 



Total 6950 3080 5670 



When exclusive grain farming is followed, the 

 annual losses of fertility from a farm of 160 acres are 

 28,500 pounds of nitrogen, 3000 pounds of phosphoric 

 acid, and 5500 pounds of potash. 



On a similar farm of 160 acres the crops are rotated 

 as described in Section 326. The amounts of fertility 

 in the products sold, the crops raised and consumed 

 as fodder, and the food and fuel purchased, are given 

 in the following table. 



