BARLEY. 95 



Dyer has been investigating the subject of " The analytical Dyer's 

 determination of probably available 'mineral' plant-food in c j^^^. ^ 

 soils"; 1 and, at the suggestion of Professor Armstrong, one sted soils. 

 of the Rothamsted Trust Committee, he asked whether we 

 could supply him, for the purposes of his investigation, with 

 samples of soils from some of the experimental fields at 

 Rothamsted, of which the manure and crop history was 

 known. Accordingly, in 1889, we gave him facilities for 

 taking samples of the surface-soil, to a depth of 9 inches, 

 from twenty-two of the plots in the experimental barley-field ; 

 and we also provided him with samples which had been col- 

 lected in 1882, from a few selected plots, to the depth of 

 three times 9 inches. 



In all these samples Dr Dyer has determined the total 

 potash, by acid, fusion, &c. ; the amount dissolved by hydro- 

 chloric acid, and the amount taken up by a 1-per-cent citric 

 acid solution ; also the amounts of phosphoric acid, by hydro- 

 chloric acid, and by a 1-per-cent solution of citric acid. Dr 

 Dyer's results, obtained on the surface-soils of the series of 

 twenty-two plots, show at a glance comparative exhaustion or 

 accumulation of both potash and phosphoric acid, whether 

 hydrochloric acid, or the dilute citric acid solution, was used. 

 There are, indeed, among these numerous results, some appa- 

 rently inconsistent quantitative indications ; but these are 

 probably attributable to irregularities in the soils themselves, Difficulty 

 and therefore to the difficulties of sampling, rather than to ™™™ffa 

 those of analysis. 



It will be useful to refer a little more in detail to the re- 

 sults obtained on the soils of plot 2a and plot 4a ; the manure 

 and crop history of which has been pretty fully illustrated by 

 the results given in Tables 29 and 30, and the discussion of 

 them. It would appear that not more than two-thirds of the 

 potash estimated to be accumulated where it was supplied, Soilaccum- 

 was taken up by hydrochloric acid ; but that approximately ^/jXand 

 the whole of the accumulated phosphoric acid was so taken phosphoric 

 up. Hence it may be judged that much of the residue of the acid - 

 supplied potash had gone into more fixed combinations 

 within the soil than was the case with the phosphoric acid. 



Then as to the citric acid results, it may be observed that 

 they are so far accordant that the sample of the surface-soil 

 of the potash -exhausted plot taken in 1882 showed more 

 potash than that taken in 1889, when the exhaustion was of 

 course greater. Again, the citric acid determinations on the 

 soil with potash-supply showed more so taken up from the 

 1889 than from the 1882 sample ; the accumulation having 



1 Trans. Chem. Soc, 1894, p. 115. See also the discussion on his paper, 

 Proc. Chem. Soc, No. 134 (1893-94), p. 37. 



