214 



FARMYARD MANURE 



[chap. 



In considering the results of these last two experi- 

 ments, it must be remembered that such a long duration 

 of the residues of farmyard manure would not be per- 

 ceptible in practice : they only become apparent when 

 the soils are cropped to a state of exhaustion that would 

 never be met with in ordinary farming experience. 



Table LXVI,— Total Produce per acre of Barley Plots, 

 SHOWING Residual Effects of Dung. 



Since only a portion — and that not the largest — of the 

 nitrogen of farmyard manure is readily available, if it is 

 the only manure supplied the crop in a good season 

 is often unable to obtain nitrogen rapidly enough, even 

 though very large quantities are lying dormant in the 

 soil. As an example, we may take the Rothamsted 



