Devoted to Agriculture, Horticulture, and the Household Arts. 



'■ W : 



Agriciilture is the nursing mother of the Arts. 



Tillage and Pasturage are the two breasts of 



[Xenophon. 



the State. — Sully. 



J. E. WILLIxlMS, Editor. 



AUGUST & WILLIAMS, Prop'rs. 



Vol. XX. RICHMOND, VA., JULY, 1860. No. 7. 



Liebig's Letters on Modern Agriculture. 

 Letter IV. 



Up to a few years ago, scientific agricul- 

 ture taughc, and all practical men firmly be- 

 lieved, that the productiveness of a soil was 

 dependent on the quantity of humus, or car- 

 bonaceous remains of a preceding vegetation, 

 contained in it. Without raising doubts on 

 the efficacy in certain cases of the organic 

 matter in farm-yard manure, it may be as- 

 serted that nobody who possesses any know- 

 ledge of the matter, now believes that the, 

 produce of a field in carbonaceous substan- 

 ces bears any proportion to the amount* of 

 humus in the soil, and that its fertility can 

 in reality be estimated, as was fori^erly sup- 

 /p^d, by this humus. 



We have now obtained more exact infor- 

 nation on the part played by humus in ve- 

 get<4tion, and can predict in what cases its 

 presence will be beneficial or hurtful. We 

 know that it is only useful when the soil 

 contains in sufficient quantity the fixed min 

 oral constituents serviceable to y>iant.s ; and 

 that it is without action when these are 

 wanting. By its decomposition in the soil, 

 humus forms a source of carbonic acid, by 

 which the fixed elements of food are ren- 

 dered soluble, and capable of being distribu- 

 ted in all directions. 



In his remarkable experiments on the ac- 

 tion of the salts of ammonia, Lawes obtain- 

 ed in twelve years from an acre of the same 

 field, by the use of mineral substances and 

 salts of ammonia, produce in wheat and 

 straw, amounting to 51,995 lbs. From a 

 second acre manured in the same way, the 

 return reached 53,182 lbs. By the use of 

 pure mineral manures, there was obtained 

 frpm these two fields a greater amount of 

 produce, to the extent of 18,525 lbs. in one 

 case, and 19,713 in the other, than from an 

 unmanured field of similar size. It is quit€ 

 certain that by the employment of farm-yard 

 manure, a similar, if not higher, return 

 would have been obtained from both fields. 

 There can, however, be no doubt that in 

 both cases the salts of ammonia had taken 

 the place, and produced the efl'ect of the de- 

 caying organic matter of this manure ; and 

 it is not improbable that the same cause was 

 in operation in augmenting the produce. 



It has been abundantly proved by facts, 

 that the action of the salts of ammonia is 

 no way proportional to the amount of nitro- 

 gen in them ; hence it is evident that the 

 salts as such, or the acids of the salts, must 

 take part in the effisct produced. The pre- 

 cise nature of this co-operation is, however, 

 not yet distinctly made out ; and from this 

 cause has arisen the sjreat discordance in the 



