MANURE LOSES ORGANIC MATTER BY AGE. 



100 parts Stable Manure J year old.* 

 Wuter ....... 79-3 



Cor i Visible substances - 14*04 ) on ._ 

 Ashes 6 66 5 ^ ' 



100.0 



Now that we k."0'«" tNat the proportion of the mineral food of 

 plants increases with the age of the dung, that old dung may- 

 contain 4 to 6 times more of it than fresh dung, an explanation is 

 furnished of the relatively greater action of the former, and of 

 the preference accorded to it by farmers of experience. 



It has been mentioned in the preceding part of the chapter, 

 that animal excrements may be replaced in agriculture, by other 

 materials containing their constituents. Now, as the principal 

 action of the former depends upon their amount of mineral food 

 so necessary for the growth of cultivated plants, it follows, that 

 we might manure with the mineral food of wild plants, or in 

 other words, with their ashes ; for these plants are governed 

 by the same laws, in their nutrition and growth, as cultivated 

 plants themselves. Thus, these ashes might be substituted for 

 animal excrements ; and if a proper selection were made of them, 

 we might again furnish our fields with all the constituents 

 removed from them by crops of cultivated plants. The vast im- 

 portance of ashes as a manure is recognised by many farmers. 

 In the vicinity of Marburg, and in the Wetterau, such a high 

 value, is attached to this costly material, as a manure, that the 

 farmers do not object to send foi t to a distance of 18 or 24 miles. 

 The importance of this manure will be more obvious, when it is 

 considered, that wood-ashes lixiviated with cold water contain 

 silicate of potash, in exactly the same proportion as straw 

 (10 Si 3 , + KO) ; and that, in addition to this salt, it contains 

 considerable quantities of phosphates. 



Different kinds of wood- ashes possess very unequal value as 

 manure. Thus, the usi.e.-* of the oak are of the smallest, those 

 of the beech of the greatest v:»<ue. Wood-ashes from oak contain 

 4 to 5 per cent, oi" phctj*hotes ; those from the beech contain the 

 fifth part of their weight of these salts. The quantity of phos- 



• Annales de Chirnio ct de Physique, iii. Serie, 237. 



