BY ADDITION OF EARTHS. 251 



have already referred, p. 242, on the classification and de- 

 scription of soils, to several modes of amelioration. In this 

 chapter we design to describe at length, these and other modes 

 of improvement, and to explain the chemical and mechani- 

 cal principles upon which the various methods are based. 



The following topics may fairly include all that is impor- 

 tant on this branch of the subject. 



1. Improvement of the soil by adding earths not existing 

 in it, or existing in too small quantities. 



1. Improvement of the soil by draining and irrigation. 



2. By fallow crops and turning in green crops. 



3. By rotation or interchange of crops. 



4. By root culture. 



5. By manures. 



6. By tillage. 



As the subject of manures is one of very great importance 

 to the farmer, and, as it is somewhat distinct from the other 

 modes of improvement, it will, in connection with that of til- 

 lage, occupy a separate chapter. 



In the discussion of the above topics, it will be necessary 

 to repeat many principles already suggested. As an apology 

 for this, we simply urge the great importance to the farmer of 

 thoroughly understanding the application of these principles 

 in all their connections and relations. 



Sect. 1 . Improvement of the Soil hy the Addition of Earths 

 not existing in it, or existing in too small quantities. 



This mode of improvement was described generally in the 

 chemical classification of soils. A few remarks only need be 

 added here, particularly applicable to the soils of New Eng- 

 land, and, with a few exceptions, to this country. 



1. Carbonate of lime.* It is hardly necessary to repeat 



* There is no subject, respecting which there is a greater diversity 

 of opinion, among practical farmers, than that of the application of 

 lime. It is said by some, to burn up the vegetable matter ; while it is 



