THE BROADBALK WHEAT SOILS. 
137 
mineral food, and have thus left more root residue in the subsoil in 
the later years, the decay of which would show an increased quantity 
of phosphoric acid in an easily soluble form. 
The same thing is to be noticed in the third 9 inches. 
Id connection with the 1893 results, the solvent action of alkaline 
sails on the phosphates of the subsoil was pointed out. This was most 
strikingly brought out on plats 5 and 7. Unfortunately, we have no 
analyses representing these plats in the earlier years, but we have the 
series of plats, 11, 1l\ 13, and 14, all receiving ammonium salts and 
phosphates, plat 11 without any alkaline salts, and plats 12, 13, and 
1 1 with sodium, potassium, and magnesium salts, respectively. In 
most rases we find thai in ilie second and third depths there is not 
very much difference between the samples of L865 and those of 1881, 
but there appears to be distinct evidence of accumulation in both the 
second and third depths between ls.M and l s< * 3, owing to descent of 
mineral phosphates. 
To >ho\\ how the results for the three periods compare quantita- 
tively with 1 he estimated addil ions and removals to and from the soil, 
I may here give a table taken from the Royal Society paper on the 
subject, showing how the excess or deficiency both of total and of 
citric-acid-soluble phosphoric acid, as against the unmanured plat 
(plat •')), compares with the expected excess per acre on each plat 
calculated from the known add it ions and removals of phosphoric acid 
to and from the soil. These data are given for the three periods of 
twenty-two years, thirty-eight years, and fifty years, respectively; 
Table IZ.—Broudbalk wheat soils— Sttmplrs vollecteil in ISM. issi, and IS'jS. 
[Plats 7, 13, 1 1. 1-*, 11, and 5.] 
After 22 years 
(1844 
1885): 
put IS 
Plat 14 
Plat 12 
Plat 11 
After 38 years 
U844- 
ls.M i: 
PlatU 
Plat 12 
Plat. 11 
After 50 years 
(1814- 
1898): 
Plat 7 
Plat 13 
PlatU 
Plat 12 
Plat 11 
Plat 5 . 
Estimated 
excess of 
phosphoric 
acid over 
plat calcu- 
lateil from 
known addi- 
tions and 
removals. 
Excess of 
total phos- 
phoric acid 
Excess i +) or deficiency ( — ) of phosphoric 
acid soluble in 1 per cent citric-acid solu- 
tion, as compared with plat 3. 
over plat 3, 
found by 
analysis in 
first 9* inches 
of soil. 
First 9 
inches. 
Second 9 
inches. 
Third 9 
inches. 
Whole 27 
inches. 

Lbs. per 
acre. 
Lift] 
1.198 
1,1ft] 
1.175 
Lbs. per 
acre. 
881 
it-:, 
1. 114 
959 
Lbs. per 
acre. 
+ 433 
+ 423 
+ 451 
+ 428 
Lbs. per 
acre. 
-19 
-13 
-19 
Lbs. per 
acre. 

+14 
+ 6 
+ 14 
Lbs. per 
acre. 
+ 414 
+ 424 
+ 430 
+ 423 
1,986 
2.1(45 
8,019 
2.081 
1,763 
1,604 
1.789 
1.374 
+ 801 
- 7."^' 
! SOU 
+ 661 
- 3 
-11 

- 8 
- 6 
- 3 


+ 792 
+ 738 
+ 809 
+ 653 
2. 452 
8,687 
8,867 
2.651 
2. 75!) 
3.049 
2. 100 
2,359 
8,838 
8,866 
2, 151 
2. 72.' 
+ 1.216 
+ 923 
+ 944 
+ 869 
+ 848 
+1,462 
- 8 
-37 
-48 
-16 
-35 
+29 
+25 
-14 
+ 6 
- 3 
-11 
+42 
+1,233 
+ 872 
+ 902 
+ 850 
+ 802 
+1,533 
The descent in the continuously dunged plat, 2b, is strongly brought 
out in botli the second and third depths when either the 1805 or the 
