MANURES AND FEKTILIZERS. 1 



do clover and certain leguminous plants. However, 

 tobacco must get its nitrogen from the soil. This ele- 

 ment must, therefore, be present in sufficient quantity, 

 and also in a thoroughly available form, and intimately 

 diffused throughout the soil, owing to the short period in 

 which the plant development can be effected. Nitrogen 

 is obtained from a number of waste products and chem- 

 icals, prominent among which are cottonseed meal, 

 castor pomace, linseed meal, tankage, dried fish scrap, 

 dried blood, dried animal matter, sulphate of ammonia, 

 and nitrate of soda. Many growers use these and other 

 chemicals, while others prefer the prepared fertilizers of 



FIG. 17. PERMANENT BED, WITH BOTH GLASS AND CLOTH FRAMES. 



commerce that are rich in available nitrogen, and are pre- 

 pared expressly for this crop. 



Availability. Tests have been made at the Con- 

 necticut experiment station to find out the crop-pro- 

 ducing power of nitrogen, supplied in various forms. 

 This was determined, not by chemical analysis, which 

 practically fails to throw much light on the subject, but 

 by the quantity of nitrogen which the crop took from 

 the fertilizer. The crops were grown on artificial soil 

 that contained only traces of available nitrogen, but all 

 the other elements of plant food were present in excess 

 of the crop needs. Of course, a single crop cannot take 



