FERTILIZATION AND FERTILIZERS 143 



bad as a crop of weeds, as it will waste too much 

 moisture. 



Commercial and mineral fertilizers (figure 76). If we 

 could always get enough stable manure, we should need no 

 other, and nothing else was thought of until it was found that 

 it was impossible to get enough manure to go around, and 

 keep up profitable crops in the fields. The reason is that a 

 portion of the fertility of the land is always carried off in 

 what is sold from the farm. 



When this was recognized, diemists analyzed stable 

 manure and Ijlants to find out what is needed, and then tried 

 to find other materials from which potash, phosphoric acid, 

 and nitrogen might be obtained. When it was found that 

 ^^vones contain much phosphoric acid T they were ground, and 

 bone meal became a much-prized fertilizer. Bones were 

 brought even from South America and other countries to 

 Europe. Then guano } the dung of sea birds living on islands 

 <Dff the coast of Peru, was brought and long used in large 

 quantities; but now there is but little guano left. It sup- 

 plied the same substances as stable manure, but in much 

 more effective form. 



j) : Chile saltpeter. Soon after, it was found that there are in 

 Chile large deposits of saltpeter, which contains the most 

 effective (nitric) form of "itrf^fir 1 \ Many millions of tons 

 of this Chile saltpeter have been and are now being brought 

 from Chile, and have greatly helped to keep up the crops of 

 Europe. Much is also now used in the United States. 



Potash salts. Then it was discovered that near ^ 



in eastern Prussia there are, alongside of common or rock 

 salt, enormous deposits of salts of potash; and these are 

 now being mined in large amounts and supply the entire 

 world. 



