THE HKOADBALK WHEAT SOILS. 
105 
Table 57. — Broadbalk wheat sotb, sample* collected in October, 1893 — Plats 7, 13, 
l.'f, / ". //. (iiul .'. rccciriiaj chemical fertilizers, including phosphates. 
Annua] manuring. 
Full minerals and ammonium 
salts — 
Phosphates, potassium ami 
ammonium salts 
Phosphates, magnesium and 
ammonium salts 
Phosphates, sodium and am- 
monium salts 
Phosphates and ammonium 
salts only 
Full minerals without ammo- 
nium salts 
Estimated 
excess of 
phosphor 
ic 
aere over 
plat cal- 
culated 
from 
known ad- 
ditions and 
removals. 
Excess of 
total phos- 
acfdper phoricacid 
per acre, 
found by 
analysis In 
first !» 
inches of 
soil. 
I '"in, <ls. 
2. IBB 
2,687 
2, in;? 
•'..<-'A 
2. :.v.» 
8,011 
Pi minis. 
8,110 
2,359 
2.:«{ 
8, S8B 
8, 181 
'J. 7 
Excess ( + ) or deficiency (— ) of 
phosphoric acid I per acre) sol- 
uble in 1 per cent citric-acid 
solution, as compared with 
plat 8. 
First !• 
inches. 
Sec, 
9 inches. 
Third 9 
inches. 
1 to 27 
inches. 
Pint nils. 
4-1.21** 
Pounds. 
— 8 
Pounds. 
+25 
Pounds. 
+1,233 
+ 923 
-37 
— H 
+ 872 
+ 944 
-48 
+ 8 
+ 902 
• sen 
-16 
- 3 
+ 850 
+ 848 
-88 
-11 
+ 802 
+ 1.-M2 
+88 
+42 
+1,533 
II will be seen thai the greater pari of the calculated excess of 
phosphoric acid is actually found in the surface soils, namely, from 
7!Mo '.U percent. It would appear thai in the course of years some 
of the phosphoric acid has descended Lower, but it is to be remem- 
bered thai the acrumulat ions arc calculated OH the supposition that 
the soils were all originally alike in phosphoric-acid contents, and, 
farther, that most of the deficit between the calculated accumulations 
and those actually found in the surface soil are comprised within a 
difference equal to only 0.01 percent of phosphoric acid calculated on 
the surface soil. Nevertheless, as the difference is always in the 
direction of deficiency, it seems probable that on the whole it is 
attributable to descent. Unfortunately, the Datura] variations in the 
total phosphoric acid of the subsoils are too great to enable us to 
verify the subsoil accumulation of total phosphoric acid. 
Broadly speaking, the results show beyond doubt that the unused 
phosphates, though applied in a soluble form, are mainly retained 
near the surface. 
Of the total phosphates added to the soil in the fertilizers, probably, 
nine-lenths would be in a condition originally soluble in weak citric- 
acid solution; but the unused portion, even of the originally soluble 
phosphates, would enter into more or less firm combination with the 
bases of the soil, as shown by the retention of its main bulk in the 
surface soil. It is of interest to see how much of the accumulated 
quantity is still to be found in the condition of ready solubility in 
weak citric-acid solution. Of the quantity found in t his condition, a 
part will no doubt be due to root and stubble residue, but in these 
plats the main portion found in the surface soil may be taken as due 
to unappropriated manure. 
The proportion found is at once seen to be large, but variable, and 
