86 



THE ROTHAMSTED EXPERIMENTS. 



Potash in 

 the crop as 

 influenced 

 by season 

 and man- 

 ures. 



stance of the grain of the differently manured plots, in the 

 different seasons. It is seen that there is much greater vari- 

 ation in the proportion of the potash in the different seasons 

 with the same manure, than there is with the different 

 manures. Further, the seasons showing the highest amount 

 of potash were of much higher maturing character than those 

 showing the lowest amounts. 





TABLE 27. — Highest, Lowest, and Mean Amounts, of Potash and 

 Phosphoric Acid, per 1000 Dry Substance. 



Per 1000 dry grain. 



Highest. 



Lowest. Mean 



Per 1000 dry straw. 



Highest. 



Lowest. 



Mean. 



POTASH. 



phosphoric acid. 



Phosphoric 

 acid in the 

 crop as in- 

 fluenced by 



Next it is seen that there is still greater, indeed enormous, 

 variation in the amount of potash in the dry substance of 

 the straw, with the same manure, in different seasons. There 

 is also great variation according to manure ; comparatively 

 little when there was full supply, but considerable without 

 manure — that is, with exhaustion. 



Turning now to the phosphoric acid in the grain, there is 

 here again much more variation in different seasons with the 

 same manure than with the different manures. But whilst 

 season and j n the case of potash there is the higher proportion in the 

 better seasons, in that of phosphoric acid there are lower 

 amounts in the dry substance in the better seasons. In fact, 

 high amount of potash in the ash, and in the dry substance of 

 the grain, is, as a rule, associated with high maturation — that 

 is, with high proportion of starch ; whilst high proportion of 

 phosphoric acid is generally associated with low maturation, 

 and with high proportion of nitrogen. 



The proportion of phosphoric acid in the straw also varies 

 more with season than with manure, and it is the highest in 

 the worst seasons. 



