SOURCES OF NITROGEN 



293 



about twenty per cent of nitrogen. It is also abundant in meat 

 scraps, dried blood and cottonseed meal. All of these materials 

 are very expensive and should be used with great care and good 

 judgment. Nitrate of soda is most likely to be wasted as it is 

 soluble in' water and may be washed or leached away unless the 

 growing crop uses it up immediately. Plant the crop first, and 



■J - * * 



Fig. 204. — After being starved for years this tree was made productive by feeding with acid 

 phosphate and nitrate of soda. (Ohio Station.) 



after it is up and growing well the nitrate may be applied and 

 cultivated into the soil. Some of the other forms in which nitrogen 

 L used are very slow in changing to available forms; some of these 

 are garbage tankage, leather scraps, hair, etc. The source of 

 nitrogen should be known to the user. This is a strong argument 

 for the home mixing of fertilizers. The agricultural value is not 



