VALUE OF POTASH 111 



half of the diagram refers to the second period, 1895-1902, 

 when potash was being used on Plot 2. 



The dotted columns in the diagram represent the crops on 

 Plots 1, where no mineral manures are used with the dung ; the 

 cross hatched columns represent Plots 2, to which in the first 

 period superphosphate was added ; the black columns the 

 same Plots 2 in the second period, when potash was also being 

 employed. Each of the pairs of columns represents a different 

 nitrogenous cross-dressing. 



From the left-hand half it is evident that superphosphate 

 when used with dung has produced no effect upon the crop 

 during the nineteen years of the first period. With no other 

 nitrogenous manures, or when nitrate of soda is used as a 

 cross-dressing, there is a small increase from the use of super- 

 phosphate, but it seems to cause even a falling-off when added 

 to ammonium -salts or rape cake and dung. 



Turning now to the effect of sulphate of potash when added 

 to dung, as represented by the right-hand diagram in Fig. 16, 

 we find that the potash produces a very marked effect. During 

 this last period the crops on Plots 2, receiving potash and 

 phosphates, have been much superior to those on Plots 1, 

 receiving dung alone ; although in the earlier period, when 

 phosphates but no potash were used on 2, the two series of 

 plots were practically equal. The increase caused by potash is 

 naturally most seen in Series O, A, C, and AC ; in Series N, 

 which is cross-dressed with nitrate of soda, much less benefit 

 is seen for the addition of potash. 



Considering the large amount of potash contained in dung, 

 and the enormous residue which must have accumulated by 

 the yearly application of 14 tons per acre for the last forty-seven 

 years, the result is very striking, as showing the dependence of 

 the mangold crop on an abundant supply of potash. The appli- 

 cation of farmyard manure is generally considered to supply 

 sufficient potash to remove the need for any further specific 

 manuring with potash salts even to so potash-loving a crop as 

 mangolds, but these experiments show that even when dung 



