OFFICIAL INSPECTIONS 62. Ill 



produced upon the farm and replace that sold off in the crops. 

 It has been a matter of great concern to those officially inter- 

 ested in agriculture that New England agriculture is not self 

 maintaining. That is, it has been necessary to look outside of 

 its borders for the supphes of plant food. Phosphoric acid is 

 found in abundance in this country. Various refuses furnish 

 large amounts of organic nitrogen. Mineral nitrogen in the 

 form of ammonia salts is obtained from coke plants and gas 

 works as a by-product. It is also obtained directly from the air 

 by synthesis. All of the nitrogen in the form of nitrate of 

 soda is, however, imported from South America. 



While ordinary farm manures carry some potash, and 'such 

 materials as sea weed and wood ashes contain potash, the 

 world's usable supply of potash has come from the mines of 

 Germany. The fact that war might make the potash of Ger- 

 many or the nitrate of soda of South America outside of the 

 reach of the American farmer, has been a matter of great con- 

 cern for years to the leaders in agricultural thought. This fear 

 is realized in this terrible European war now raging which pre- 

 vents the importation from Europe of the German potash salts. 

 There is probably from a quarter to a third as much potash in 

 the United States as would normally be used in the 191 5 fer- 

 tilizers, and hence the question which confronts the fertilizer 

 manufacturer and the user of fertilizers is how to use this 

 limited supply to the best advantage. 



An acre of soil to the depth of one foot in the potato growing 

 districts of Maine carries from 4 to 6 tons of potash salts solu- 

 ble in strong acid. Gradually by soil action this potash is ren- 

 dered available to growing plants. With the three and four 

 year rotation fairly common in Maine potato districts the crops 

 remove from 225 to 300 pounds of potash per acre. Three 

 hundred bushels (no barrels) of potatoes will remove about 

 90 pounds of potash, 50 bushels of oats about 45 pounds of 

 potash, and two crops of two tons of clover and timothy about 

 180 pounds. Most of the fertilizer used in these rotations in 

 the potato growing sections is applied for the potato crop. The 

 application will carry from 125 to occasionally 200 pounds of 

 potash per acre. Hence it is evident that in this rotation there 

 is a constant drawing, although small, upon the reserve stock of 



