142 THE BOOK OF WHEAT 



pathogenic ferments, which may subsequently infect the health of 

 man and beast. These ferments may attach themselves to veg- 

 etables and thus enter the animal organism, or they may remain 

 with a suspended vitality for an indefinite period in the soil and 

 awaken to perniciousactivity when a favorable environment is 

 secured." 



Vast stores of fertilizing materials are continually being 

 washed from the earth by floods, and carried away by streams 

 and rivers. The Seine river thus annually carries two million 

 tons of silt, a greater weight than the merchandise which its 

 waters transport. The Yar carries seaward yearly 23,000 tons 

 of nitrogen, and one cubic meter of water per second from this 

 stream could be made to produce crops valued at 35,000 francs 

 each" year. The river Durance, an Alpine stream, annually 

 carries silt, the fertilizing power of which is equal to 100,000 

 tons of stable compost or excellent guano. It would take 

 119,000 acres of forest trees to yield the carbon that this volume 

 of silt contains. 



FERTILIZER EFFECTS 



Effect on Germination. In general, fertilizers never seem to 

 aid in the germination of seeds, and may be harmful if used in 

 large quantities. One per cent of muriate of potash, or of 

 sodium nitrate, is very detrimental, whether applied directly, 

 or mixed with the soil. Phosphoric acid and lime are much less 

 injurious, and may be harmless if not used in excess. It is 

 safest not to bring commercial fertilizers into immediate con- 

 tact with germinating seeds, and the effect of chemicals applied 

 to seeds before they are planted is no index of their action in 

 this respect when used as fertilizers. When injury does re- 

 sult, it is chiefly to the young sprouts during the time between 

 when they leave the seed coat and when they emerge from 

 the soil, the seed being affected but slightly, if at all. Salts 

 injurious to wheat seedlings have been given in the following 

 order: Magnesium sulphate, magnesium chlorid, sodium car- 

 bonate, sodium sulphate and sodium chlorid. Different varie- 

 ties of wheat vary in their ability to resist the same toxic salt, 

 as does also one variety in different salts. 



Effect on Yield and the Supply of Plant Food. There seems 

 to be a certain minimum yield of wheat which a soil will give 



