than to phosphorus in the fertiHzer, although even here the 

 best outcome has not been reached unless both phosphorus 

 and potassium were applied. 



The lesson from these tests seems to be, therefore, that in 

 respect to these two elements of fertility — phosphorus and 

 potassium — we should study the character and composition 

 of the crop, and especially should remember that neither 

 phosphorus nor potassium is ever wholly absent from any 

 plant, and therefore that the supply of both these elements 

 must be looked after. 



It is true that these elements are found in all soils, and ap- 

 parently in liberal quantity, as compared with the needs of the 

 crop. In the Ohio soils under experiment we find in the upper 

 7 inches of an acre from 700 to 1,200 pounds of phosphorus, 

 yet it is impossible to grow a full crop of any kind until we add 

 some material containing phosphorus in an easily soluble form. 

 More surprising yet is to find 16 to 18 tons of potassium in the 

 same 7-inch acre, and yet so small an application as 8^ pounds 

 of potassium per acre, carried in 20 pounds of muriate of 

 potash, has added 5 bushels of corn to the yield, as a twelve- 

 year average, when added to a dressing of phosphorus. 



But what would have happened if the 16 to 18 tons of potas- 

 sium stored in our soil had been as easily soluble as common 

 salt or muriate of potash? Ages before man came to inhabit 

 the earth the potassium would all have been in the sea. Thus 

 we understand why it is that the great store of potential plant 

 food shown by the chemist to be in the soil may have no prac- 

 tical value for crop production, and why we cannot depend 

 upon chemical analysis as a guide to the use of fertilizers 

 until the chemist shall have discovered some reagent key that 

 will unlock these stores in the same manner as do the vital 

 agencies which are working in the soil. Bryant sang of — 



. . . the sluggish clod 

 Which the rude swain turns with his share 

 And treads upon. . . . 



but we now know that this "sluggish clod" is inhabited by 

 living organisms, infinitely small and infinite in number, upon 

 whose work depends the existence of all living things. 



