Methods of Use of Fertilizers 205 



phoric acid is the dominant fertilizer ingredient for tur- 

 nips, Swedes, Indian corn (maize), sorghum and sugar 

 cane; and potash is the dominant or ruling element for 

 peas, beans, clover, vetches, flax and potatoes. It must 

 not be understood that this system advocates only single 

 elements, for the others are quite as important up to a 

 certain point, beyond which they do not exercise a con- 

 trolling influence in the manures for the crops of the three 

 classes. This special or dominating element is used in 

 greater proportion than the others, and if soils are in a high 

 state of cultivation, or have been manured with natural 

 products, as stable manure, they may be used singly to 

 force a maximum growth of the crop. Thus, a specific 

 fertilization is arranged for the various rotations, the crop 

 receiving that which is the most useful. There is no doubt 

 that there is a good scientific basis for this system, and that 

 it will work well, particularly where there is a reasonable 

 abundance of all of the plant-food constituents, and where 

 the mechanical and physical qualities of soil are good, 

 though its best use is in "intensive" systems of practice. 

 It cannot be depended upon to give good results where the 

 land is naturally poor, or run down, and where the physical 

 character also needs improvement. 



A system based upon the necessity of an abundant supply of 



the minerals. (Wagner System.) 

 Another system which has been urged, notably by Ger- 

 man scientists, is based upon the fact that the mineral 

 constituents, phosphoric acid and potash, form fixed com- 

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

 leached out, provided the land is continuously cropped. 

 They remain in the soil until used by growing plants, while 

 the nitrogen, on the other hand, since it forms no fixed 



