REPORT OF TEE APPLE AND PEAR CONFERENCE. 



43 



for many years. Notwithstanding conditions so conducive to the 

 extension of disease, there is at the present time still no appear- 

 ance of active canker. The trees have been carefully inspected 

 by some experienced pomologists, who, doubtless, will confirm 

 my statement. Short as is the time during which the trees have 

 been submitted to the treatment, I can only conclude that the 

 arrest of the disease is due to the supply of elements of food 

 required by the trees, of which a sufficient quantity was not 

 previously contained in the soil. 



The food required by a plant is a complicated mixture of 

 many elements, all of which are necessary for its well-being; the 

 complete absence of one of them would be fatal ; a deficient 

 supply of one would arrest its development, and render it subject 

 to disease. Nothing is more instructive and conclusive on this 

 point than the copies of photographs of plants grown for the 

 purpose of testing the effect of manures more or less complete, 

 to be found in treatises on the subject. That of " Ville on 

 Artificial Manures," published by Longmans, contains many such 

 illustrations, which clearly show that when the soil contains 

 every element of fertility but one it remains absolutely barren. 

 For instance, in a soil without potash, the vine makes no growth. 



It remains to say that the manures necessary to restore a tree 

 to health vary as the soils ; although the ashes of the wood of the 

 apple tree contain 71 per cent, of lime — an exceptionally large 

 quantity — it would not be necessary to supply this element on a 

 lime formation ; nor would soda be required in a soil near the 

 sea, although on other geological formations or situations a 

 deficiency of one or both may be the cause of canker. Like 

 conditions apply to the other elements. 



Various soils require such manures as will supply their 

 various deficiencies ; but, as it is most difficult to ascertain even 

 by analysis what may be the deficiencies of a soil, the practical 

 way of dealing with the subject is to study the analysis of the 

 ashes of the plant in question, and to use a manure which is 

 composed of these elements ; for instance, 



The ashes of the wood of the apple tree contain : 



Potash Soda Ifapmesia Lime Iron Phosphorus Sulphur Silica Chlorine 

 12-0 1-6 5-7 71-0 — 4-6 2*9 1-8 0*2 



and those of the fruit : 



35-7 26-1 8-3 4-1 1-40 13-6 G'l 4-3 — 



Ville lays down the rule that soils generally contain sufficient of 

 all the mineral elements except potash, lime, and phosphorus, 

 and the gaseous element nitrogen, and says it is only necessary 

 to supply to the soil manures which contain these four. This 

 may be sufficient for the general purposes of cultivation, but more 

 recent experiments have conclusively proved that the addition of 



