886 Notes on Manures for December. [Dec.^ 



NOTES ON MANURES FOR DECEMBER. 



Rothamsted Experim€7ital Station, Harpenden, Herts. 



Does Manuring pay? A further Example. — In last month's 

 notes the question was raised whether manuring pays, and the 

 answer was given that it does when it is properly carried out. 

 Assuming that a farmer can grow^ a crop at all at present prices 

 he will make more out of a good crop than of a poor one. It is 

 quite fallacious to suppose that under-production on British 

 farms would help farmers by forcing up prices or in any other 

 way; it would simply result in more imports. Nor is there any 

 reason why farmers should despair and give up because of the 

 difficult times through which they are now passing. Last month 

 an instance was given showing that the best return to the farmer 

 is obtained when a bold pohcy is adopted and the fertiliser 

 dressing is not too stinted. 



This is shown by the following experiment on potatoes carried 

 out this season at Kothamsted : — 



As in the cases previously quoted, the double dressing of sulphate 

 of ammonia has given more than double the return of the first ; 



cwt. sulphate of ammonia gave an additional crop of IJ tons 

 per acre of potatoes, while 3 cwt. gave an additional 3 tons 8 cwt. 

 per acre. Now the price of 3 tons vS cwt. of potatoes is 

 not yet anything like as low as that of 3 cwt. of sulphate of 

 ammonia, even after the cost of lifting, storing, marketing, etc., 

 is thrown into the account. 



The experiment illustrates the undoubted truth that, after a 

 certain point is reached, further additions of fertiliser do not 

 continue to increase the yield of crop at the same rate, although 

 the increase may still be profitable. In the present instance a 

 further IJ- cwt. sulphate of ammonia (making 4J cwt. in all) 

 gave a further increase of 6 cwt. of potatoes per acre over that 

 given by 3 cwt. : this is a small but by no means negligible 



Sir John Russell, D.Sc, F.E.S., 



Increase due to each 

 Yield per additional 1^ cwt. 

 acre. sulphate of a m m onia. 



tons. tons per acre. 



10 tons farmyard manure ; phosphates and 

 potash and — 



No nitrogenous manure ... 6*0 



H cwt. sulphate of ammonia 7'5 



1-5 

 1-9 

 0-3 



