54 BOOKS AND CURRENT LITERATURE 



and N equivalents of a fertilizer mixture be simply represented by the 

 actual K, P, and N contents perhaps in terms of percentages of the 

 total weight of the mixture. It would tend greatly toward clarification 

 of a somewhat complicated and frequently misunderstood set of rela- 

 tions, if this plan might be followed in field studies, just as it has gen- 

 erally been followed in the most satisfactory studies of water and sand 

 cultures. If a given acre-ration of a fertilizer mixture actually con- 

 tains 200 pounds of potassium there seems to be no valid reason, for calcu- 

 lating this amount in terms of possible K 2 many more than for calcu- 

 lating it in terms of possible KC1, KN0 3 , K 2 CO;j, K2SO4, or any other 

 atomic group in which K may occur. If anyone desires to know how 

 much of the oxide might be secured from 200 pounds of potassium, he 

 can readily find this out, but if our fertilizer terminology were clear and 

 direct it is doubtful if anyone would care to know the answer to such a 

 question. If any manipulation is to be performed upon the actual 

 content of the mixture, as represented by weight, it is immediately 

 suggested that this ought to result in giving us the content in terms of 

 molecular units, as gram-molecules, etc. But these are readily obtain- 

 able from the weight itself. As an illustration of these points, the 

 following statements refer to the example mentioned above. The 

 given acre-ration actually contains 200 pounds of potassium. It 

 represents a possible 240.9 pounds of K 2 0, a possible 353.2 pounds of 

 K0CO3, a possible 516.9 pounds of KNO3, etc. Finally it actually con- 

 tains 2317.2 gram-molecules of potassium. 



The paper, here considered should be familiar to all who are inter- 

 ested in field experimentation on fertilizers and also to all who are 

 interested in the salt nutrition of either plants or animals. The prob- 

 lems of salt nutrition are so complicated (by numerous possible vari- 

 ables) that a clear grasp of any concrete case is hardly to be secured 

 without resorting to some such system of tabulation or graphical 

 representation as that furnished by the triangular diagram for three 

 components, or the pyramidal diagram for more than three components. 

 Schreiner and Skinner are pioneers in the employment of this system 

 and it is to be hoped that they, as well as others, will continue in its 

 employment. Agricultural practice needs planned experimentation, 

 and much of it, and this system of graphical representation permits 

 logical planning and exhaustive interpretation of results. — Raf. B. 

 Espino, 



