22 



the salt. This is to some extent mitigated by additions of dung, 

 but the crop always falls below that obtainable from the muriate 

 or the sulphate. The results at Rothamsted are : — 



Yield of Potatoes when Sulphate of Potash is Used = 100. 



These fertilisers affect the quality of the potatoes. Of the com- 

 plete manured plots, those receiving sulphate of potash produce 

 tubers with the highest percentage of dry matter. 



The tubers grown with low grade potash salts (kainit, sylvinite) 

 are the lowest in dry matter content, coming out even below those 

 grown without potash. 



The percentage of starch in the dry matter is an important 

 quality factor, and in all tubers so far analysed the value comes 

 out higher for the sulphate of potash than for any of the other 

 salts. 



Magnesium sulphate continues to give interesting results ; 

 its effect on potatoes has been beneficial at several centres though 

 we cannot yet explain why. 



Complete 



\i till 



No Magnesium 

 Sulphate 



With Mat" 



Sulphate 



1922 



No 

 Dung. 



Rothamsted. 



100 



m 



97 



No 

 Dung. 



1923 



100 

 104 



lOK 



Dung. 



100 



104 

 104 



Blaydon 

 1922 

 No 

 Dung 



100 



108 



Dung. 



100 



111 



Walbottle. 



1922 

 No 

 Dung. Dung. 



100 

 118 



100 

 P2!> 



Newton 



Abbot. 



1922 



Dung. 



100 



117 

 120 



