11(5 
INVESTIGATIONS ON KOTHAMSTED SOILS. 
A comparison of the citric-acid-soluble potash, however, appears to 
be much more instructive as to the potash condition of the soils. 
The ratios are as follows: 
Number of plats. 
Mode of manuring. 
Ratio of citric-acid-soluble pot- 
ash to that in the 7 nonpotash 
plats. 
First 
inches. 
Second 9 
inches. 
7 plats 
3 plats 
1 plat . 
1 plat . 
Without potash for forty years 
Potash dressed 
Dung fifty years 
Dung nine years. 
l.(K) :1 
6.75:1 
10.67 : 1 
9.17:1 
1.00 : 1 
3.63:1 
6.00:1 
3.65:1 
These figures are so striking- that but little comment on them 
appears to be necessary. The chemically manured potash plats show 
in the first- 9 inches nearly seven times as much citric-acid-soluble 
potash as those left without potash dressings, and in the second 9 
inches about three and a half times as much, while even in the third 
depth there is nearly twice as much, showing that even in these 
clayey loams potash salts do, to an appreciable extent, find their way 
downward into the lower subsoil. The greater portion of the accumu- 
lation, however, is (in accordance with the generally accepted views 
of the chemistry of fairly heavy soils) found to be in the upper soil, 
where the potash appears to enter into more loose combination with 
the constituents of the clay. 
In the continuously dunged soil, where the estimated excess of pot- 
ash applied has been much greater, Ave find in the top soil more than 
ten times as much citric-acid-soluble potash as in the nonpotash plats, 
in the second 9 inches six times as much, and in the third 9 inches 
nearly three t imes as much; while even in the plat dunged for nine 
years only we find nine t imes as much in the top soil, t hree and a half 
t hues as much in the second 1) inches, and twice as much in the third. 
It would seem as though the potash of the dung, possibly in some 
organic state of combination, descends more easily into the subsoil 
than do the inorganic potash salts. This point, however, will claim 
our ail en1 ion Later. 
In the paper on the Hoos field barley soils a tentative conclusion 
wa^ drawn thai the percentage of citric-acid-soluble potash in the 
surface soil indicative of potash hunger would for cereals probably 
lie below 0.005. On considering the results of the wheat soil analyses 
and other results obtained in the interim by workers who have applied 
the method to other soils known from experience to be responsive to 
the influence of potassium salts, the lecturer would now be inclined 
U) modify this conclusion by suggesting that when a soil contains as 
much as 0.01 per cent of citric-acid-soluble potash as determined by 
this process it may be regarded as not demanding any special appli- 
cation of potassium salts. 
