434 ACTION OF RAPE-DUST ON WHEAT AND BEANS. 



bring into a state of fermentation, even when mixed with the liquid 

 manure of the farm-yard. 



3°. Rape-dust. — When rape seed is exhausted of its oil, it comes 

 from the press in the form of hard (rape) cakes, which, when crushed 

 to powder, form the rape-dust of late years so extensively employed as 

 a manure. It is occasionally mixed with farm-yard dung, and applied 

 to the turnip crop, but its principal employment has hitherto been, I 

 believe, as a top-dressing for the wheat crop, either harrowed in with 

 the seed in October, or applied to the young corn in spring. 



Rape-dust requires moisture to bring out its full fertilizing virtues ;- 

 hence it is chiefly adapted to clay soils or to such as rest upon a stiff 

 subsoil. It is seldom applied, therefore, to the barley crop, and even 

 upon wheat it will fail to produce any decidedly good effect in a very 

 dry season. Several interesting circumstances have been experi- 

 mentally ascertained in regard to the action of rape-dust, to which it 

 is proper to advert : — 



a. That in very dry seasons it may produce little benefit upon tur- 

 nips, potatoes, and other crops, while in the same circumstances the 

 effect of guano may be strikingly beneficial. Thus in one experi- 

 ment, made in 1842, upon unmanured land sown with turnips — 



16 cwt. of rape-dust gave 3| tons of bulbs per acre. 



2 cwt. of guano gave 5 do. 

 Unmanured gave 3i do. 



And in another, in the same season, upon unmanured land — 

 1 ton of rape-dust gave 14^ tons of bulbs per acre. 



3 cwt. of guano gave 23i do. 

 Unmanured gave 12 J* do. 



. Again, upon potatoes, planted without other manure, in three ex- 

 periments the produce per acre, in tons, was as follows : — 



Unmanured. 1 ton Rape-dust. 3 cwt. Guano. 4 cwt. Guano. 



White Don Potatoes — 12i 18^ — 



Red Don Potatoes ...!... 6| 10 — 14i 



Connaught Cups 5| 13 — 13| 



In none of the above experiments did the action of the large quan- 

 tity of rape-dust equal that of the comparatively small quantity of 

 guano — though, from being buried in the soil, the difference was less 

 striking in the case of the potatoe crops. 



b. Rape-dust may actually cause the crop to be less than the land 

 alone would naturally produce — if in a dry season it be laid on in 

 any considerable quantity. 



Thus in 1842, in an experiment upon Oats, made at Lennox Love — 

 16 cwt. of rape-dust gave 45 bushels. 

 2 cwt. of guano gave 68 do. 

 Unmanured soil gave 49 do. 

 In this property of injuring the crop, when rain does not happen to 

 fall, rape-dust resembles very much those saline substances which, as 

 we have seen, may often be applied with much advantage to the land. 



c. Yet it would appear to exercise less of this evil influence upon 

 wheat and beans, and n similar circumstances. Thus in the same 



• See AppendLx, No. VIU. 



