410 



ORGANIC CHEMISTRY. 



be obtained. Rye, buckwheat, and clover are among 

 the plants best adapted to the purpose. Vegetable mat- 

 ter is thus added to the soil, which, in its decay, hastens 

 the decomposition of the soil itself. 



What is said 1028. DEFICIENCY OF ONE OR MORE CON- 



of defitien- sTiTUENTs. The comparative exhaustion 



ties in partic- 



ular constitu- of some one or more of the constituents 

 of the soil, is a much more frequent oc- 

 currence. It is commonly the result of the cultiva- 

 tion of the same crop during many successive seasons, 

 and the consequent reduction of those materials which 

 the particular plant requires in largest proportion. De- 

 terioration of soils from this cause, is repaired by an 

 artificial supply of the failing ingredients. It is more 

 wisely guarded against by such a rotation of crops as 

 shall make different demands upon the soil in succes- 

 sive years. 



What is said 1029. MAINTENANCE OF FERTILITY. - 



f the e / ect f The effect of decomposing animal matters 



decomposing 



animal matter on the soil, has been already considered. 

 the soil ? return the very material which was 



abstracted from the soil, with the addition of nitro- 

 genous matter, originally derived from the air by the 

 growing plant. In an enlightened system of rural 

 economy, the production of these materials in large 

 quantity and their careful preservation, is therefore an 

 object of paramount importance. The addition of 

 gypsum or dilute sulphuric acid to fermenting ma- 

 nures, is of great advantage in retaining their ammonia 

 in the form of sulphate, and preventing its escape into 

 the air. When additional ammonia is required, it is 



