98 RESULTS WITH POTATOES 



We have thus in these fine seasons a return of 25 cwts. of 

 potatoes for i cwt. of sulphate of ammonia. 



2. The Glasgow Experiments. Experiments on the 

 potato crop, grown in its ordinary place in a Scotch rotation, 

 have been carried out during three years, 1895-97, on several 

 series of farms. The results are of considerable practical 

 importance, though, from the absence of plots receiving only 

 cinereal manures, it is only rarely possible to ascertain the 

 exact return obtained from the sulphate of ammonia employed. 



The great importance of potash salts as an ingredient of a 

 potato manure is abundantly illustrated. The addition of 

 2 cwts. of sulphate of potash to a manure consisting of sulphate 

 of ammonia and superphosphate increased the weight of dressed 

 saleable potatoes by gj cwts. on two farms in 1895 '> by 19^ 

 cwts. on two other farms in 1896 ; and by 27 cwts. on twelve 

 farms in 1897. In the 1897 experiments, the addition of 4 cwts. 

 of superphosphate, and i cwt. of sulphate of ammonia, to 15 

 tons of farmyard manure, increased the average yield of sale- 

 able potatoes by only 4f cwts., while a further addition of 

 i cwt. sulphate of potash increased the produce by 14 cwts. 



In each series of experiments farmyard manure has been 

 applied alone, we are thus able to compare its effect with that 

 given by ammoniacal manures. In the experiments on twelve 

 farms in 1897, tne saleable potatoes obtained from 2 cwts. 

 sulphate of ammonia, 2 cwts. sulphate of potash, and 6 cwts. 

 of superphosphate, were only 3^ cwts. per acre less than those 

 produced by 15 tons of dung. When 700 Ibs. of kainite were 

 substituted for the sulphate of potash, the ammoniacal manure 

 beat the dung by 8J cwts. On two farms in 1896, 3 cwts 

 sulphate of ammonia, 2 cwts. sulphate of potash, and 6 cwts. 

 superphosphate, produced 22 cwts. more saleable potatoes than 

 20 tons of dung. 



The Glasgow experiments also furnish examples of the 

 increase over an unmanured crop which may be obtained by 

 the use of ammoniacal manures when no dung is employed. 

 On twelve farms in 1897, the use of 2 cwts. sulphate of ammonia, 

 6 cwts. superphosphate, and 700 Ibs. of kainite, increased the 

 yield of saleable potatoes by 3 tons. On two farms in 1896, 



