EXPERIMENTS AT ROTHAMSTED 87 



superphosphate alone as representing the produce of ash 

 constituents without ammonia. Proceeding thus, we have 

 a return of 7-9 cwts. of hay for i cwt. of sulphate of ammonia 

 during the first twenty years, and a return of 8'8 cwts. in the 

 second twenty years, when the autumn made hay is included. 

 These figures are of course more or less above the true return 

 from the ammonia on plot 9, they are possibly, however, not 

 too high for the return on plot 13, where the crop is con- 

 siderably larger for the same amount of ammonia applied. 



\Ye may, if we like, ascertain the practical value of the 

 ammonia salts and ash constituents applied to plot 9 by com- 

 paring the cost of the manure per acre w r ith the value of the 

 hay obtained. The increase of hay on plot 9 over the unmanured 

 produce is represented by nearly 30 cwts. per acre during the 

 first twenty years of the experiment. In the second twenty 

 years the increase is 27-7 cwts. in the first crop, and 7-2 cwts. 

 in the second crop, the total increase being nearly 35 cwts. 

 \Ye can hardly value the increase of hay on this plot at less 

 than 5 an acre. The Rothamsted manures are not selected 

 for their cheapness, the main object being to employ salts 

 of definite composition. By using kainite we can, however, 

 supply in one manure the potash, soda, and magnesia which 

 are applied as distinct salts in the Rothamsted experiments. 

 Substituting kainite for the alkali salts used at Rothamsted, 

 the appropriate manure for plot 9 should not cost above 70-80 

 shillings per acre. 



On plot 13 we have an increase over the unmanured produce 

 of 36-3 cwts. during the first twenty years. In the second 

 twenty years there is an increase of 32-4 cwts. in the first crop, 

 and 1 1 -6 cwts. in the second crop, or a total increase of 44 cwts. 

 of hay. The money value of this hay we may probably place 

 at 6. 10. o. per acre. The manure applied is the same as that 

 used on plot 9, with the addition of 2,000 Ibs. of chopped straw 

 per acre. 



It is evident that on both plots there is a fair margin for 

 profit. The character of the hay on plot 9 is moderately good, 

 but that on plot 13 is better, and equal to all the requirements 

 of the farmer. 



