110 THE COMPOSITION OF CROPS IN 



ings of lime, soot, or salt, if they do not hinder their operations, 

 at least act as a manure to the plant. Handpicking of the 

 larger caterpillars is rarely to be thought of except in a garden, 

 but a regiment of young ducks is an infallible remedy. And 

 finally, if a farm is in good " heart," the crops on it will be the 

 better able to withstand their depredations. 



THE COMPOSITION OF CROPS IN AVERAGE PRODUCE 



PER ACRE. 



By William Hay, Tillydesk, Aberdeenshire. 



[FTemium, the Medium Gold Medal], 



The elementary substances of which plants are composed are 

 very commonly spoken of as divided into two more or less dis- 

 tinct portions, — organic and inorganic, — or what is, perhaps, more 

 definite, into combustible and incombustible, this latter portion 

 I being also called the Asli. This ash forms only a very small 

 proportion of the weight, and still less of the bulk of all vegetable 

 I substances. Yet it is with this ash, w4th its amount and the 

 elements of which it is composed, that the cultivators of the 

 soil have mainly to concern themselves. In addition, there is, 

 however, just one other elementary substauce of importance as 

 a constituent of all our cultivated crops, namely. Nitrogen ; and 

 this element again forms only a very small proportion of the 

 organic matter of plants. The value of all manures and of all 

 fertilising substances whatever, consists simply in the amount of 

 this ash, or of one or more of its elements, and of this nitrogen 

 which they supply in available form. 

 r Of this so-called inorganic matter or ash, vegetable sub- 

 stances, generally speaking, contain only from about 1 to 4, or 

 j at most 6 or 7 per cent, of their whole mass. The rest, that is 

 ' the great bulk and weight — 94 per cent, and upwards — of all 

 ; vegetable, and, for that matter, of all animal substances also, 

 consists of organic or combustible matter ; and this organic 

 matter as^ain consists almost entirelv of carbon and the elements 

 of water. The carbon is mainly obtained from the atmosphere, 

 and the water, from the generally abundant supply in the soil. 

 It thus appears that the farmer has not to concern himself at 

 all about providing, in the shape of manure or otherwise, the 

 materials which go to make up the greater part of the bulk of 

 his crops. The organic matter, we have just said, consists mainly, 

 but it does not consist entirely, of carbon and w^ater. It con- 

 tains in small amount relatively, but nevertheless as an indis- 

 pensable part of its organised structure, the other element to 

 which reference has been made, namely, nitrogen — an element 



