Behaviour of Soda and Silica. 



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 asso- 

 ciated with low maturation and 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. 



With regard to the behaviour of soda, very much more of 

 this ingredient was found in the crops grown without its 

 supply in manure, but where potash was deficient, than 

 where soda was annually supplied. This is strikingly shown 

 in the average amounts per acre per annum in the total 

 crops, grain and straw together. Thus, over a first period of 

 ten years, 1852-1861, the average amounts of soda in the 

 total crop were, without any supply in the manure of either 

 potash, soda, or magnesia, 8'401b., and with the supply of all 

 three, only 3'841b. ; over a second period of ten years, 

 1862-1871, without the supply 15'211b., and with the supply 

 only 3'691b. ; and lastly, over a third period of five years, 

 1872-1876, without the supply H'851b., and with the supply 

 only 3'271b. Thus, then, not only was there much more soda 

 taken up, or retained, by the plant where it was not supplied 

 than where it was, but there was the more soda taken up the 

 less the supply of potash. 



The chief point of interest with reference to silica is, that 

 its percentage in the ash of barley grain ranges from 17 to 

 more than 20, whereas in the ash of wheat grain it ranges 

 only from about 0*5 to about 1'5 per cent. ; or, taking the pro- 

 portion of silica to 1000 dry substance of grain, in barley it 

 ranges from four to five parts, and in wheat only from about 0*1 

 to about 0'3 parts. This difference is obviously due to the chaff 

 being adherent in the case of the barley grain, and not in that 

 of the wheat grain, a circumstance leading to, as might be 

 expected, less definiteness in the mineral composition of the 

 grain of barley than in that of wheat. 



