152 TALKS OX MANURES. 



bushel, and 3,000 Ibs. of straw, removes from the land on which it 

 is grown, 20 Ibs. of phosphoric acid. The clover-soil analyzed by 

 me, consequently contains an amount of phosphoric acid in a 

 depth of only six inches, which is equal to that present in 247} 

 average crops of wheat ; or supposing that, by good cultivation 

 and in favorable seasons, the average yield of wheat could be 

 doubled, and 50 bushels of gram, at CO Ibs. a bushel, and 6,000 Ibs. 

 of straw could be raised, 124 of such heavy wheat-crops would con- 

 tain no more phosphoric acid than actually occurred in six inches 

 of this clover-soil per acre. 



" The mere presence of such an amount of phosphoric acid in a 

 soil, however, by no means proves its sufficiency for the produc- 

 tion of so many crops of wheat ; for, in the first place, it can not 

 be shown that the whole of the phosphoric acid found by analysis, 

 occurs in the soil in a readily available combination ; and, in the 

 second place, it is quite certain that the root-fibres of the wheat- 

 plant can not reach and pick up, so to speak, every particle of 

 phosphoric acid, even supposing it to occur in the soil in a form 

 most conducive to ' ready assimilation by the plant.' 



" The calculation is not given in proof of a conclusion which 

 would be manifestly absurd, but simply as an illustration of the 

 enormous quantity in an acre of soil six inches deep, of a constitu- 

 ent forming the smaller proportions of the whole weight of an 

 acre of soil of that limited depth. It shows the existence of a prac- 

 tically unlimited amount of the most important mineral constitu- 

 ents of plants, and clearly points out the propriety of rendering 

 available to plants, the natural resources of the soil in plant- 

 food ; to draw, in fact, up the mineral wealth of the soil, by thor- 

 oughly working the land, and not leaving it unutilized as so much 

 dead capital." 



" Good," said the Deacon, " that is the right doctrine." 



" The roots," continues Dr. Voclcker, " from one square foot of 

 soil were cleaned as much as possible, dried completely at 212, 

 and in that state weighed 240 grains. An acre consequently con- 

 tained 1,493} Ibs. of dried clover-roots. 



" The clover-roots contained, dried at 212 Fahr. , 



Organic matter* 81.33 



Mineral matter, f (ash) 18.67 



100.00 



* Yielding nitrogen 1.6S5 



Equal to ammonia 1 .'. ; x"> 



t Including insoluble eilicious matter, (clay and sand) 11.67 



