MINERALS USED AS FERTILIZERS. 



73 



also with the different feeds consumed by them ; but the aver- 

 age composition of farmyard manure is approximately given 

 thus by Wolff and others : 



ANALYSES OF VARIOUS FARMYARD MANURES. 



1. Average composition of fresh farm manure (Wolff). 



2. Average composition of moderately rotted farm manure (Wolff). 



3. Average composition of very thoroughly rotted farm manure (Wolff). 



4. Mixed cow and horse manure from a bed two feet thick, accumulated during 

 the winter in a large covered yard, and packed solid by the tramping of cattle (The 

 analysis by F. E. Furry). 



5. " Box Manure," consisting of mixed manure of bullocks, horses, and pigs 

 (Way, Royal Agric. Soc. Journ., 1850, II., 769). 



It is thus seen that the percentage of the important plant- 

 foods in stable manure are minute when compared with those 

 commonly found in "commercial" fertilizers. Nor are they 

 so much more available for plant absorption than the latter; 

 a very large proportion is not utilized at all the first year, and 

 unless the amount applied is very large it hardly carries the 

 supply needed for the usual crops. 



It is now well understood that its efficacy is largely due to 

 the important physical effects it produces in the soil. It helps 

 directly to render heavy clay soils more loose and readily till- 

 able. If well " rotted ' or cured it also serves to render 

 sandy, leachy soils more retentive of moisture ; and the humus 

 formed in its progressive decay imparts to all soils the highly 

 important qualities discussed later on (chapt. 8). More than 

 this, the later researches have shown that stable manure acts 

 perhaps most immediately upon the bacterial activity in the 

 soil, greatly increasing it not only directly by the vast numbers 

 of these organisms it brings with it, but also in supplying ap- 

 propriate food for those normally existing in the soil (see 



1 And soda. 



