108 Agricultural Chemistry. 



may come from the crude salts. Nitrogen should be applied as 

 nitrate of soda, because in this form it is immediately useful, 

 and thus may be applied in fractional amounts, and at such times 

 as to best meet the needs of the plant at its different stages of 

 growth, with a reasonable certainty of a maximum use by the 

 plant. Thus no unknown conditions of availability are involved, 

 and when the nitrogen is so applied, the danger of loss by leach- 

 ing, which would exist if it were all applied at one time, is ob- 

 viated." (Voorhees.) 



System based on the analysis of the plant. ' ' Still another sys- 

 tem is based on the food requirements of the plant as shown by 

 the analysis of the plant itself. The amount of plant food re- 

 moved from each acre of ground is calculated from the analysis 

 of the plant and a corresponding amount is returned to the soil. 

 Different formulas are, therefore, recommended for each crop, 

 and in these the nitrogen, phosphoric acid and potash are com- 

 bined in the same proportions in which they are found in the 

 plant. Experience shows that it is necessary to add amounts of 

 these fertilizers to the soil that will supply more plant food than " k 

 is removed by the crop if the maximum results are desired. This 

 system may result in a large yield, but cannot be considered an 

 economical method of feeding the plant, as one or more of the 

 elements is likely to be applied in excess of the requirements of 

 the crop. It does not take into consideration, for instance, the 

 fact that a plant which contains a large amount of one element 

 of plant food may possess unusually great -power of procuring 

 that element from the soil. The principle underlying this sys- 

 tem, of course, is the idea that to maintain the fertility of the 

 soil unimpaired an amount of plant food equivalent to that re- 

 moved by the crop must be returned to the land. To this extent 

 the system is similar to the use of barnyard manure, but is not 

 so effective." 



Money crop system. " Another system used in ordinary or 

 extensive farming is to apply all the fertilizer to the money ci 





