152 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
usually receive annually about 56 pounds of chlorinper acre in their 
dressing of ammonium salts. It may be that the effect of the calcium 
in the superphosphate is to produce some physical difference in the 
soil which makes it more retentive of chlorids. 
The quantity of chlorin present in the three aggregate depths, 
except on plat 04 and plat A2, does not differ much from that found 
in the most nearly corresponding plats in the Broadbalk wheat field. 
PHOSPHORIC ACID AND POTASH. 
A set of samples of the Hoos field barley plats was kindly drawn 
for me in the autumn of 1889 by Sir Henry Gilbert, for the purpose 
of investigations as far as regards their phosphoric acid and potash 
contents, as determined by the citric-acid process, on which I was 
then working. The samples represented the surface soil only, and 
were taken from only one place in each plat, as the immediate object 
was rather one of qualitative than of quantitative investigation. 
The results of the analyses have been fully discussed in an earlier 
paper, referred to on p. 96; but it may be convenient, for future 
reference, that the figures should find a place here. 
PHOSPHORIC ACID. 
The phosphoric acid results may be conveniently stated in the fol- 
lowing table (Table 82), in which the plats are grouped with special 
reference to their phosphatic manuring, the corresponding plats of 
each section being brought together. The table shows the percentage 
of total phosphoric acid in the fine dry soil, and also the percentage 
dissolved b}' a 1 per cent solution of citric acid; and also the yield of 
barley (both grain and straw) in the year following the sampling. 
Table 82.— Hoos field barley soils, samples collected in the autumn of 18S9 — 
Phosphoric acid determinations. 
Series. 
Plat. 
Animal manuring since 1852. 
Phosphoric acid in 
fine dry soil. 
Yield per acre 
in 1890. 
Total. 
Dissolved 
by 1 per 
cent solu- 
tion of 
citric acid. 
Barley. 
Straw. 
O 
1 
1 
1 
1 
3 
3 
3 
3 
Per cent. 
0.099 
.05*7 
.104 
.106 
Per cent. 
0. 0055 
.0060 
.0067 
.0071 
Hushels. 
13 
24i 
29 * 
31J 
(Uct. 
i* 
12? 
14i 
15? 
A 
AA .... 
AAS . 
O 
A 
AA.... 
AAS 
Ammonia salts only 
Nitrate of soda only 
Nitrate of soda and silicate of soda 
Average of above four plats 
Potash, etc. (no phosphates) 
Ammonia salts, potash, etc. (no phos- 
phates). 
Nitrate of soda, potash, etc. (no phos- 
phates). 
Nitrate of soda, silicate of soda, potash, 
etc. i no phosphates). 
Average of above four plats 
.102 
.0063 
24J 
12* 
.121 
.102 
.104 
.105 
.108 
. 0100 
.0081 
.0082 
.0112 
.0094 
9* 
23* 
28 
36* 
1 
15* 
m 
13J 
