37 



immediately available as plant food. The after effects of rich 

 and poor manure will be far more alike than their first 

 effect. 



The rapidity with which applications of organic manure 

 will disappear in the soil depends upon their quantity, and on 

 the rapidity of the oxidation proceeding in the soil, the manure 

 disappearing much more rapidly in some soils than in others. 

 In all the instances we have quoted in which the visible effect 

 of farmyard manure has continued for a long time, there has 

 been previously a continuous application of the manure every 

 year for a considerable number of years ; by thus supplying 

 more than the soil can destroy a substantial residue is accumu- 

 lated. We have equally seen, in other instances, that the 

 application of nitrogenous manure once in a rotation has its 

 effect exhausted before the rotation is concluded. With any 

 considerable increase in the quantity of farmyard manure 

 applied its residual effect will increase in a still greater propor- 

 tion ; a double dressing of manure should give more than a 

 double after effect where the circumstances of the case 

 admit of the effect being shown. All these points must be 

 taken into account in any attempt to value the unexhausted 

 residue of organic manures. 



VALUATION OF EESIDUES IN POOB AND KICK SOILS. 



The facts I have brought before you lead, I think, dis- 

 tinctly to the conclusion that a different scale of valuation 

 should be employed when dealing with land of very different 

 quality, or receiving very different quantities of manure. We 

 may conveniently classify farms for our present purpose as 



(1) those whose actual fertility is distinctly below the average ; 



(2) those in a condition of average fertility; (3) those in 

 which very liberal manuring is practised. 



The first-named class will include those farm lands the 

 natural fertility of which is very low, and which yield 

 remunerative crops only when the soil is systematically 

 supplied with plant food by means of manures, or the organic 

 residues of fodder crops. It will also occasionally include 

 land of naturally fair quality, which by a long course of 

 exhaustive treatment has reached a low state of fertility ; of 



