169 



Many deductions may be drawn from the above Table as vre have 

 before hinted, and every farmer can make the deductions most suit- 

 able to his own case and calculations. There are some, however, of so 

 general a character that it may be well to mention them here. These are 

 of much importance as general principles in guiding the agriculturists, 



Liebig first proposed to divide plants into groups or classes, accordino-; 

 as one or another alkali or element predominated in their ashes. This 

 view has been followed by some agricultural writers, while it has been 

 rejected by others, from the fact Avhich we have already mentioned, that 

 the seed or fruit, in many cases, differs very much from the stalk, or 

 straw of the plant, and one kind of element might characterize the stem 

 and another the fruit or seed. Prof. Norton, however, in his " Elements 

 of Scientific Agriculture," mentions five classes of ash, three of which 

 take the lead. 1st. The grains, where phosphoric acid predominates. 2d. 

 The roots, where potash and soda abound. 3d. The grasses, where lime 

 becomes quite important. 4th. The various kinds of straw, where silica 

 is from one-half to two-thirds of the whole weight. 5th, includes treeS;^ 

 such as fruit and forest trees, whose ash, in numerous cases, contains 

 more of lime than of any other substance. 



These facts may not appear to be corroborated by the above Table, because 

 that in the Table, the analysis takes the plant as a Avhole, not separatino* 

 the ash of the seed from that of the stalk. This classification may be of 

 use in many cases when the whole crop is not removed from the field,, 

 as is the case with most root crops, the tops being left in the field to 

 decay, and, of course, to return their constituents to the soil. It is also 

 of importance in indicating to the farmer, what is the efiect of return- 

 ing the straw of his crops to the field, while the grain or seed is removed. 

 The general impoverishing eflfect of continued cropping not being so 

 great, in this case, as when the straw is not returned in the form of long 

 manure, and yet the impoverishment of some important element essen- 

 tial to a specified crop, may be as effectually and surely produced in the 

 one case as in the other. 



The Table enables us to understand the efi'ect of cropping upon the soil, 

 both in connection with and without special manures. We cannot better 

 elucidate this point than by giving the illustrations of Prof. Norton, in 

 his "Elements of Agriculture," Suppose, in the first place, that, as is 

 too often the case, wheat or any other grain has been grown upon a new 

 soil, crop after crop, and nothing returned in the shape of manure, the 

 12 



