10 
the highest and the lowest in fixing power being both sandy soils 
but differing in organic-matter content. The fact that the fixation 
of phosphoric acid from the calcium salt was not excessively greater 
than that from the potassium salt was probably due to the fixation 
being largely a result of the action of iron and aluminum compounds 
and only a partial reversion of the calcium salt. Crawley * found 
that upon irrigating Hawaiian soils immediately after application of 
water-soluble phosphate one-half of the phosphoric acid remained in 
the first inch of soil, nine-tenths in 3 inches, and practically all in 6 
inches of the surface soil. These results indicate the absolute neces- 
sity of turning all applications of phosphate under by deep plowing 
in order to get the best results. Otherwise the rain is not able to 
wash it down to the roots, and consequently the dissemination of 
this fertilizer is incomplete. 
At the point where these series were stopped the soils had appar- 
ently lost none of their fixing power. This fact lends very strong 
proof to the theory that the concentration of the soil solution with 
regard to phosphoric acid is not increased by the addition of this 
element in moderate quantities either as a soluble or insoluble salt; 
also, that while there are differences in the concentration of the solu- 
'tion in different soils, they are due to factors other than the solubility 
of the salt in water. 
ABSORPTION OF POTASH. 
For the study of the absorption of potash a solution of potassium 
sulphate, containing about 200 parts per million of potassium (K) 
was used. The soils were the same as used in the phosphate series, 
and the method of percolation was through a column of 100 grams of 
the soil placed in glass tubes, as already described. At the outset 
the solution percolated quite rapidly, but after five days much more 
slowly in soils Nos. 292 and 428, and extremely slowly in soil No. 
448. A precipitate, apparently of ferric hydrate, formed upon stand- 
ing overnight in the extract from soil No. 292. After about one 
month the percolation from soil No. 448 (yellow clay soil) became 
so slow as to be several hundred cubic centimeters behind the rest 
of the series. However, strange to say, about one week following 
the date of above conditions, the percolation in soil No. 448 was 
faster than with the other soils, and when the experiments were 
stopped soil No. 474 was percolating the most slowly of all. 
In order to get a clear conception regarding the absorption of pot- 
ash, it is of some value to know the effect of leaching the soils with 
water upon the solubility of this element. The table following 
throws some light upon this. 
i Jour. Amer. Chem. Soc, 24 (1902), p. 1114. 
