196 Fertilizers 



the same natural character, located equally well, will not 

 always show the same results from the application of 

 fertilizers, because in the one case the cropping has been 

 such as to result in the rapid exhaustion of one, rather than 

 the three specific fertilizer elements ; while in the other, the 

 cropping may have been quite as severe, but has been help- 

 ful because judicious rotations have been used and improved 

 methods practiced. It may be that in the one case, there 

 may have been a continuous cropping of wheat, for exam- 

 ple, and only the grain sold from the farm, in which case 

 there would be a much more rapid exhaustion of the nitro- 

 gen and phosphoric acid than of the potash; and if this 

 continuous wheat-cropping has been continued for a long 

 time, an application of the phosphates only may result in 

 quite as large an increase in crop as if both phosphates and 

 potash salts were applied, because the potash exhaustion 

 has been less rapid than that of the phosphoric acid, and 

 the addition of potash would simply add to the probably 

 abundant quantities already there. On the other hand, 

 if the cropping has been timothy hay, the removal of the 

 potash would have been greatly in excess of the phosphoric 

 acid, and consequently a fertilization with a greater propor- 

 tion of potash, or even this element alone, of the minerals, 

 may result in quite as large returns as if the fertilization 

 had consisted of both phosphoric acid and potash. In 

 fact, if the land had been cropped continuously with 

 tobacco, cotton, potatoes or other crop, there is likely to 

 be a much larger removal proportionately of some one 

 element, rather than proportionate amounts of all. This 

 practice results in a disproportionate removal of the con- 

 stituents, and in order to bring the land back to its capac- 

 ity for maximum production, or to equalize matters in this 

 respect, it is necessary to add to the soil the constituents 



