68 AMERICAN AGRICULTURE. 



from the sub-soil, as all plants appropriate such saline sub. 

 stances as are necessary to their maturity, and are brought to 

 their roots in a state of solution by the up-welling moisture 

 from beneath. This last is frequently a great, source of im- 

 provement. The amount of carbon drawn from the air in 

 the state of carbonic acid, and of ammonia and nitric acid, 

 under favorable circumstances of soil and crop, are large ; 

 and when buried beneath the surface, all are saved and yield 

 their fertility to the land ; while such as decay on the surface 

 lose much of their value by evaporation and drainage. In 

 the green state fermentation is rapid, and by resolving the 

 matter of plants into their elements, it fits the ground at once 

 for a succeeding crop. 



THE FALLOW SYSTEM. 



As a means of enriching lands, this was formerly much 

 practised, but it is now entirely discarded by intelligent 

 farmers. It consists in plowing up the land and exposing it 

 naked to the elements, whenever the exhaustion by tillage 

 required it. This practice is founded on the principle, that 

 plants gradually exhaust the soil of such soluble food, potash, 

 soda, &c., as are necessary to their support ; and unless they 

 are again given to it in manures, in a form suited to their 

 immediate appropriation by plants, time is requisite for dis- 

 solving them in the soil so as to enable them again to sup- 

 port vegetation profitably. Besides the loss resulting from 

 the frequent idleness of the land, naked fallows have this 

 further disadvantage, and especially in light and loose soils; 

 they are exposed to the full action of the sun and rains, and 

 by evaporation and drainage are exhausted of much of their 

 soluble vegetable food. 



This system, bad as it is, may yet be absolutely necessary 

 where grain alone is raised, and no manure is applied. But 

 it is always avoidable by substituting fallow crops as they are 

 termed, potatoes, turneps, &c. with manure ; or clover or 

 other green crops, as above detailed ; by which the land is 

 cleared of weeds and sufficiently enriched for succeeding 

 cultivation. Land is equally well prepared for grain by 

 having been occupied as meadows, if they have been kept in 

 good condition by top dressing and pastures answer the 

 same purpose without them. 



