192 THE FARMER OF TO-MORROW 



in the soil, and are, therefore, not likely to 

 be leached out, provided the land is con- 

 tinuously cropped. They remain in the soil 

 until used by growing plants, while the 

 nitrogen, on the other hand, since it forms 

 no fixed compounds and is perfectly soluble 

 when in a form useful to plants, is liable to 

 loss from leaching. Furthermore, the mineral 

 elements are relatively cheap, while the nitro- 

 gen is relatively expensive, and thus the 

 economical use of this expensive element, 

 nitrogen, is dependent to a large degree upon 

 the abundance of the mineral elements in the 

 soil. It is, therefore, advocated that, for all 

 crops and for all soils that are in a good state 

 of cultivation, a reasonable excess of phos- 

 phoric acid and potash be applied, sufficient 

 to more than satisfy the maximum needs of 

 any crop, and that the nitrogen be applied in 

 active forms, as nitrate of ammonia, and in 

 such quantities and at such times as will in- 

 sure the minimum loss of the element and 

 the maximum development of the plant. 



"Page 186. Another system of fertilization 

 is based upon the theory that the different 

 plants should be provided with the essential 

 elements in the proportions in which they exist 

 in the plants, as shown by chemical analysis. 

 Different formulas are therefore recommended 

 for each crop, the constituents of which are 

 so proportionate as to meet its full needs. 



