THE aUANTITY MUST NOT BE TOO GREAT. 435 



season, 1842, and in the same locality, Lennox Love, a crop of wheat, 

 with — 



16 cwt. of rape-dust gave 51 bushels per acre. 

 2 cwt. of guano gave 48 do. 



Unmanured gave 47 § do. 



And a crop of beans, with — 



16 cwt. of rape-dust gave 38 bushels. 

 2 cwt. of guano gave 35i do. 

 Unmanured gave 30 do. 



In both'bf these cases, notwithstanding the drought, the rape-dust 

 Improved the crop, and though not sufficiently so to pay the cost of the 

 application, yet to a greater extent than the same quantity of guano. 

 It is deserving of investigation, therefore, whether rape-dust be more 

 especially adapted to wheat and beans. Even in favorable seasons 

 it may possibly prove more economical than guano as a manure for 

 these two crops (see Appendix, No. VIII.) 



d. But even in favorable seasons, and to the wheat crop, there is 

 reason to believe that rape-dust cannot be economically applied in more 

 than a certain, perhaps variable, quantity per acre. Thus four equal 

 plots of ground (nearly half an acre each,) sown with wheat, were top- 

 dressed with rape-dust in different proportions with the following results: 



With 7 cwt. the produce was 26 bushels of market corn. 



With 10 cwt. the produce was 28 do. 



With 15 cwt. the produce was 2% do. 



With 26 cwt. the produce was 27| do. 



Unmanured the produce was 22 i* do. 



In this experiment not only was the crop diminished when more 

 than 15 cwt. was added, but the increased produce was not sufficient 

 to defray the additional cost of the application, when more than 7 

 cwt. of rape-dust was put on. 



e. It may be noticed as another curious fact, that the action of 

 rape-dust is dependent upon the presence or absence of certain other 

 substances in the soil. Common salt and sulphate of soda, when 

 mixed with it under certain circumstances, lessen the effect which it 

 would produce alone, and the same will probably happen when it is 

 applied, without admixture, to soils in which these saline compounds 

 happen to be already present. Some remarks upon this interesting 

 point will be found in the Appendix, No. VIII. 



4°. Lintseed, poppy-seed, cotton-seed, and cocoa-nut cakes. — The 

 cake which is lefl when other oils are extracted from the seeds or fruits 

 in which they exist is, also, in almost every case, useful as a manure. 

 Thus the seeds of the cotton plant yield an oil and leave a cake which is 

 now used as a manure in the United States, though Httle known as yet, I 

 believe, in England. The cocoa-nut cake is employed in Southern In- 

 dia partly in feeding cattle and partly as a manure for the cocoa-nut tree 

 itself Some trials have recently been made with it among ourselves, 

 but I am ignorant of the precise results. In this country lintseed cake 

 is made in large quantity, but as it is relished by cattle, is fattening, and 

 enriches the droppings of the stock fed upon it, it is seldom applied di- 



* British Husbandry, I., p 412. 

 19 



