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soil, and that the condition of his field can be 

 improved by such means as will destroy the chemical 

 combinations of the nutritive substances present, and 

 change their state into that of physical combination. 

 We can obtain these results either by mechanical 

 or chemical means. Among the former are 

 included all the ordinary operations of husbandry, 

 such as draining, ploughing, harrowing, &c. ; 

 among the latter we include the application of 

 lime, marl, ammonia, common salt, which are not 

 intended so much as an augmentation of the ferti- 

 lizing material present in the soil, as to render 

 such material available for the nutritive processes 

 of plants. 



The mechanical operations of agriculture pur- 

 pose to prepare the soil so as to offer the least 

 resistance to the extension of the root ; and 

 to mix it thoroughly, in order that plants may find 

 sufficient nourishment equally distributed through- 

 out the field. 



The plough every year exposes a new surface of 

 soil to the action of moisture and atmospheric 

 air, which renders a fresh portion of chemically 

 combined plant-food available for the next crop. 

 To prove the importance of ploughing, it is sufficient 

 to state that of two soils of equal fertility, the best 

 ploughed one will always yield the highest return, 

 and moreover a poor but well-tilled soil will often 

 yield as much as a far more fertile but not so 



