NATURE OF A KYE SOIL. 125 



tremely fruitful soil for beans ; and a comparison of 

 the ash constituents, in the stalks and seeds of the crop, 

 with the quantity which had been added to the turf, 

 shows that the twelve to fourteen-fold quantity of these 

 ash constituents was enough to produce a very abun- 

 dant seed crop. The porous turf, saturated even in 

 its minutest particles with nutritive elements, favoured 

 in this case an enormous developement of the roots, to 

 which the largeness of the crops is due. Nothing can 

 be more certain than that its power of production 

 measured by time is very small, and that after a very 

 few harvests its fertility would vanish speedily and for 

 ever. 



That our corn fields should contain nutritive sub- 

 stances in very great abundance is the necessary condi- 

 tion for & continuance of good crops, but it is not indis- 

 pensable for one rich harvest. 



A good rye soil is one which produces an average 

 rye crop, but less than an average wheat crop. 



From what we have seen, the reason why a wheat 

 plant, which requires from the soil the same elements 

 as the rye plant, will not thrive as well as the latter 

 upon a rye soil, is founded on this, that during the 

 same period of time the wheat needs more of these nu- 

 tritive substances than the rye, but cannot obtain this 

 additional quantity. Hence, a good wheat soil which 

 yields an average wheat crop, differs from a good rye 

 soil which produces an average rye crop, inasmuch as 

 the wheat soil in all its parts contains more nutritive 

 substances, just in proportion as the wheat crop needs 

 and carries away more than the rye crop. 



A good rye soil, which is able to give and does give 

 1 per cent, of its nutritive substances to an average rye 

 crop, would necessarily yield an average wheat crop, if 

 the wheat plants growing upon it could extract 1-J- per 

 cent, of its nutriment. But, in fact, this does not take 

 place : whence it follows that the absorbent root-sur- 

 faces of the wheat cannot be half as large again as 

 those of the rye ; for, were this the case, the roots of 

 the wheat would come into contact with half as many 



