CHEMISTRY OF AGRICULTURE. 



The character of soils and the nature of vegetable constituents are 

 interesting subjects of study with all who admire the works of nature 

 and who love to investigate her laws. It is an important object with 

 the practical agriculturist ; and it should be so with every well-wisher 

 to human happiness, to produce the best and the largest quantity of 

 useful vegetable products on a given surface of soil. An examination 

 therefore, into the means which nature has provided for this purpose, 

 and the arts and late discoveries of scientific men in effecting so im- 

 portant an object, cannot be without the deepest interest to the gene- 

 ral reader as well the cultivator of the soil ; not only as it explains 

 the remarkable functions and properties of plants, but as it discloses 

 their not less remarkable adaptation to the requirements of animal 

 and human life. 



It will have been seen in previous chapters that the soil is composed 

 of two kinds of substances, organic and inorganic. The former con- 

 sists of parts of animal and vegetable matter, and the latter of earthy 

 or rocky substances. The organic matter is generally capable of 

 being burned and the parts driven off by heat, while the inorganic 

 is commonly fixed and incapable of being dissipated in that way. 

 Plants which grow upon such soil must therefore contain portions 

 of these substances. From 3 to 10 per cent, of productive soil is 

 thus composed of organic matter ; and the ash of vegetables, when 

 burned, show the amount of inorganic matter, which is generally from 

 20 to 50 per cent. The soil, if heated red, will show no great diminu- 

 tion of bulk, but if the stalk of wheat be burned there is very little 

 product. This, in a ton of wheat straw, is about 300 Ibs., and in 

 that of rye, 200 Ibs. But a ton of wheat grain yields but 40 and that 

 of oats 90 pounds of ash or inorganic matter. The organic matter 

 which vegetables have acquired by assimilating the matter of the soil, 

 constitutes, therefore, nearly its entire weight. The ultimate elements 

 of this matter, as we have before stated, consists of carbon, hydrogen, 

 oxygen and nitrogen. Thus some common plants, when dry, consist 

 of the following proportions, in pounds, of a 1000 Ibs. each : 



Carbon, Hydrogen. Oxygen. Nitrogen. Ash. 



Wheat straw 485 - 52 . 389 31-70 



Oats - 507 - 64 - 367 22 - 40 



Potatoes 441 . 58 - 439 12-50 



Hay 458 - 60 387 15 - 90 



