118 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
Table 64. — Broadbalk wheat soils, samples collected in October, 1893 — Plats 11, 
12, U, 13, 7, and 5. 
Plat. 
12 
13 
Annual manuring. 
Phosphates and ammonium 
salts only 
Phosphates, ammonium, and 
sodium salts (some potas- 
sium salts in earlier years) . . 
Phosphates, ammonium, and 
magnesium salts ( some potas- 
sium salts in earlier years).. 
Phosphates, ammonium, and 
potassium salts — 
Phosphates and ammonium, 
potassium, sodixxm, and mag- 
nesium salts. 
Phosphates and potassium, so- 
dium, and magnesium salts 
(no nitrogen) 
Estimated 
excess or 
deficiency 
of potash 
per acre in 
soil after 
fifty years 
as com- 
pared with 
plat 11 (cal- 
culated 
from 
known ad- 
ditions and 
removals). 
Excess of 
hydro- 
chloric- 
acid -solu- 
ble potash 
per acre 
found by- 
analysis in 
first 9 
nches of 
soil as com- 
pared with 
plat 11. 
Pounds. 
+ 20 
- 92 
+4,052 
+3, (562 
+5,242 
Excess or deficiency of c;itric-acid- 
soluble potash per acre found 
by analysis as compared with 
plat 11. 
First 
9 inches 
Pounds. Pounds. 
675 
21 
+1,115 - 21 
+1,971 +404 
+1,686 +519 
+2,126 +716 
Second Third 
!t inches. 9 inches. 
Pounds. Pounds. 
+ 32 
+ 53 
+288 
+299 
+523 
+ 44 
+134 
+156 
inches. 
Pounds. 
53 
+ 76 
+ 826 
+ 896 
+1,395 
As far as the hydrochloric-acid results are concerned, we find a con- 
siderable increase in the potash dissolved from the surface soils of all 
the plats which have received alkaline manures, and the increase, as 
would naturally be expected, is very much greater in the case of the 
plats which have been constantly manured with potassium salts, and 
greatest of all on plat 5, in the case of which, owing to the absence of 
a manurial supply of nitrogen, the least demand has been made on the 
mineral contents of the soil. We do not, however, find in any case 
that, in the surface soil, hydrochloric acid yields as much as even 
one-half of the calculated acreage accumulation of potash. 
We will now pass on to the citric-acid results. 
Plat 12 is calculated to contain 20 pounds of potash per acre more 
than plat 1 1. The quantity found by citric acid in the surface soil is 
21 pounds, with '.)2 pounds in the second depth, making an excess over 
plat 11 Of 53 pounds per acre. This plat (plat 12) is even now much 
more fertile than plat 11, although the equivalent of the actual pot- 
ash added has been nearly used up, and the potash in its produce is 
still annually far larger than in that of plat 11. There can be little 
doubt thai the action of the sodium sulphate annually supplied keeps 
up a considerable annual supply of available potash. 
Plal L3, with a full supply of potash, has, in fifty years, yielded 
about 1 per cenl more grain and about 9 per cent more straw than plat 
12; hut its crops have contained 2,410 pounds of potash per acre, as 
1.7 C) pounds in those of plat 12. The potash-manured crops, 
