COMMERCIAL FERTILIZER MATERIALS 447 



mineral theory propounded by Liebig ; and still later tlie dis- 

 covery of the nitrifying process almost disposed completely of 

 the belief that organic matter is used directly by higher 

 plants. It is quite certain, however, that some organic nitrog- 

 enous compounds furnished suitable material for some higher 

 plants without undergoing bacterial change and producing 

 a nitrate form of nitrogen. 



The following compounds have been shown by Hutchinson 

 and Miller^ to be readily assimilated by peas: aeetamide, 

 urea, barbituric acid, and alloxan. Formamide, glycerine, 

 cyanuric acid, oxamine, peptone, and sodium aspartate were 

 assimilated but less easily. Creatinine has been shown by 

 Skinner ^ to be used directly by plants as a source of nitro- 

 gen. Histidine, arginine, and creatine have also been found 

 in soils and it has been demonstrated that they have a direct 

 influence on wheat seedlings. 



These and numerous other investigations of this subject 

 show that amine as well as amide nitrogen is assimilated by 

 at least some agricultural plants, but to what extent most 

 of these compounds may successfully replace the inorganic 

 forms of nitrogen, such as the nitrates, has not been definitely 

 established. Certain organic nitrogenous fertilizers — as, for 

 example, dried blood — ^have a high commercial value, the 

 nitrogen in this form selling for more a pound than the nitro- 

 gen in any of the inorganic salts. Many crops, especially cer- 

 tain vegetables, are most successfully grown only when 

 supplied with organic nitrogenous material. Some ni- 

 trate nitrogen is always present under natural soil condi- 

 tions, so that crops are never limited to organic nitrogen 

 alone ; and it may be that the latter form of nitrogen is most 

 useful when it supplements the nitrate form, 



^Hutchinson, H. B., and Miller, N. H. J., The Direet Assimilation 

 of Inorganio and Orgamo Fornu of Nitrogen hy Higher Plants; Centrlb. 

 f. Bakt., II, Band 30, Seite 513-547, 1911. 



^Skinner, J. J.^ III. Effects of Creatinine on Plant Growth; U. S. 

 Dept. Agr., Bur. Soils, Bui. S3, pp. 33-44, 1911. 



