46 THE son, SOLUTION 



quantities of dissolved minerals would be found under the better 

 crops, and vice versa. An inspection of the results, however, 

 shows that no such correlation can be made, nor in fact can any 

 consistent correlation be made between the dissolved material 

 and crop, soil type, water content, depth of soil or part of the 

 growing season. 1 It appears, therefore, that in so far as the 

 field method of analyzing an arbitrarily prepared aqueous ex- 

 tract is competent, there is no evidence that there are important 

 characteristic differences in the concentration of the mineral 

 constituents in different soil solutions in the field. 



The order of concentration of the soil solution can be approxi- 

 mated from the given data, if the assumption be made that in 

 the preparation of the aqueous extract, soluble mineral constit- 

 uents are of minor importance, other than the constituents 

 already dissolved in the soil solution. The calculation is very 

 laborious, is not exact, and on account of the assumptions made 

 the actual figures obtained are of no especial value in any par- 

 ticular case. Remembering the method of making up the solu- 

 tions from which these results were obtained, it would be suffi- 

 ciently near the truth to assume an average moisture content 

 of 20 per cent., when the figures given here for the soil approxi- 

 mate those which would be obtained for the soil solution. More 

 exact calculations have been made for a large number of such 

 cases, and it has been found from this method of estimation 

 that the average composition with respect to phosphoric acid 

 would be about 6-8 parts per million, and for potash about 

 25 parts per million, figures which agree with the results ob- 

 tained for the examination of solutions extracted from saturated 

 soils by means of the centrifuge. 



1 King, however, claims that the concentration of the soil solution 

 with respect to mineral plant nutrients, is higher in the soils of the 

 northern states than in the soils of the South Atlantic states. See : 

 Some results of investigations in soil management, by F. H. King, Year- 

 book, U. S. Dept. Agriculture, 1903, pp. 159-174. Bailey E. Brown has 

 obtained some preliminary results which suggest that there may be 

 seasonal variations with respect to some of the dissolved mineral con- 

 stituents. See, Annual Report of the Pennsylvania State Experiment 

 Station, 1908-9, pp. 31 et seq. 



