phoric acid. In the case of potash, the vast deposits of Ger- Food for 

 many furnish unlimited quantities of crude material, which Plants 

 are readily converted into concentrated salts of potash, free 4* 

 from deleterious substances, and which furnish potash in im- 

 mediately available forms, and, because of their high content 

 of the essential element, the transportation charges are rela- 

 tively low per unit of constituent. Nitrogen, on the other 

 hand, is less abundant, and even though found in the form of 

 Nitrate of Soda as a natural deposit, the quantity is limited in 

 extent, as compared with the deposits of phosphates and pot- 

 ash salts. The location of the deposits in a barren country 

 makes it more expensive, too, to concentrate and to remove 

 impurities, and even when in its most concentrated commercial 

 form, it is comparatively bulky, as compared with the manu- 

 factured potash salts, thus increasing the cost of transporta- 

 tion per unit of the constituent. 



Second, because Nitrogen exists in three forms as or- 

 ganic matter, as ammonia and as Nitrate and which differ 

 widely in their rate of availability or immediate usefulness 

 to the plant. The Nitrogen in the first and most common 

 form (organic) generally undergoes a change into a Nitrate 

 before plants can make a large use of it; this change requires 

 a longer or shorter time, according to the character of the 

 material. If, therefore, we desire a large and reasonably 

 quick use of the constituent when applied in organic materi- 

 als, it is necessary, first, to select those likely to change rap- 

 idly, and second, to depend upon favorable weather condi- 

 tions, i.e., warm and moist in order that a rapid change 

 into soluble and available forms can take place, and thus 

 permit the plant to obtain its Nitrogenous food that is, it is 

 possible, in the use of these forms, which must undergo a 

 change, to get very meagre returns, though an amount is 

 applied largely exceeding that necessary for the crop, either 

 because the Nitrogen may have been in such combination as 

 to strongly resist decay, or the season may have been such as 

 to render the change, in even high-grade materials, so slow as 

 to prevent the plant from obtaining a sufficient amount to meet 

 its demands. The second, or ammonia, form of Nitrogen is 

 immediately soluble, and is readily distributed in the soil by 

 means of the soil water; it is then fixed until changed into the 

 Nitrate form, which takes place rapidly under average sea- 

 sonal conditions, though an appreciable time must intervene 



