114 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
practical meaning that they may he left out of consideration, for the 
quantity of potash dissolved by the mineral acid in these lower depths 
is vastly in excess of the potash which, from any point of view, can be 
regarded as of nearly prospective utility, and its variations are obvi- 
ously so independent of the manurial treatment and cropping history 
of the soils as to deprive them of apparent practical significance. 
The more important results may be conveniently studied in the 
following table : 
Table 62. — Broadbalk reheat soils, samples collected in October, 1893. 
Potash in fine dry soil. 
Annual manuring for 50 years 
(with only minor variations 
during the earlier years). 
Dis- 
1 solved 
by hy- 
i drochlo- 
ric acid. 
First 
inches. 
Dissolved by 1 per cent cit- 
ric-acid solution. 
First Second | Third 
9 inches. 9 inches. 9 inches. 
Average yield 
per acre, 
1889-1894. 
Wheat. Straw 
Unmanured continuously 
Unmanured continuously since 
1852 
Ammonium salts only since 1844 
Ammonium salts only since 1850 
Ammonium salts and superphos- 
phate 
Ammonium salts, superphos- 
phate, and sodium sulphate 
(some potassium salts prior to 
1852) 
Ammonium salts, superphos- 
phate, and magnesium sulphate 
(some potassium salts prior to 
1852) 
Ammonium salts, superphos- 
phate, and potassium salts 
Ammonium salts, superphos- 
phate, and potassium, sodium, 
and magnesium sulphates 
Superphosphate and potassium, 
sodium, and magne'sium sul- 
phates (no nitrogen) '.. 
14 tons farmyard manure 
14 tons farmyard manure (com- 
mencing in 1884-85) 
Per cent. 
0.220 
.219 
.240 
.234 
.197 
22:5 
Per cent. 
0.0032 
.0052 
.0032 
.0040 
.0032 
(Kill) 
Percent. Per cent. 
0.0060 0.0072 
Bushels. 
m 
240 
0024 
,0060 
.0032 
.0052 
.0028 
.0040 
IK 148 
.0044 
.0048 
.0036 
.0036 
.0036 
.0058 
.273 
.262 
.279 
. 0188 
.02:;:; 
. 0306 
. 0136 
0084 
.0140 I .0064 
.0384 
.0330 
(1221 
.0092 
.0276 I 
.0168 
.0128 
.0096 
It will be seen that we have a series of plats of which some are 
wholly unmanured, some manured with ammonium salts only, and 
several with both ammonium salts and phosphates. Of these last, one 
plat is without alkalies, one receives sodium salts, another magnesium 
salts, one potassium sails, and another all of these materials. We 
see that plat 11 without alkalies, though abundantly supplied with 
nitrogen and phosphates, lias evidently largely exhausted the readily 
available potash of the soil by comparing its recent yield of wheat 
and si raw (more especially the latter) with that of the potash plat 13. 
We also see that, either in virtue of certain applications of potassium 
salts forty years or more ago or in virtue of the solvent action on 
soil potash of the sodium and magnesium salts applied every year, 
