5i8 
Journal of Agricultural Research 
Vol. VII, No. 12 
Table; XI .—Comparative weights of rice plants grown in neutral solution with phosphates 
doubled , with ferric chlorid or citrate source of iron 
& 
& 
Green weight of stalks and 
leaves. 
Oven-dry weight of stalks 
and leaves. 
Gm, 
Gm. 
' 1-6 
28. 22 
3 * 54 
■ 7-12 
34 * 30 
4 * 24 
28. 76 
3 - 63 
19-24 
29. 84 
3 - 78 
25-30 
27*43 
3-49 
. 3*-36 
29. 42 
3-89 
37-42 
42. 12 
5-21 
‘ 43-48 
37 * 24 
4 - 56 
: 49-54 
38. 16 
4.76 
55 - 6 o 
39 * 23 
4.88 
- 61-66 
37 * 30 
4. 72 
.67-72 
34 * 5 1 
4-39 
1-12 
202. 36 
29-95 
>13-24 
192. 20 
28. 72 
/ 25-36 
181. 78 
27*33 
137-48 
189. 34 
28.85 
Nutrient solution. 
Neutral. 
Neutral, with dou¬ 
ble phosphates. 
Neutral. 
Neutral, with dou¬ 
ble phosphates. 
Neutral. 
Neutral, with dou¬ 
ble phosphates. 
Source of iron. 
O. 002 
002 
}■ 
008 
008 
. 008 
►. 008 
Ferric chlorid. 
....do. 
. .do. 
— do. 
Ferric citrate. 
do. 
Gm 
o.68 
.84 
.69 
* 74 
. 6S 
.78 
I. 20 \ 
1. 03 
I. IO 
•99 
•93 
.90 
7. 41 
7. 11 
6 . 74 
7. 21 
Average 
oven-dry 
weight of— 
eft El 
jJ 
Gm. 
3. 80 
3- 72 
4- 84 
4.66 
29- 34. 
28.* * ’ 
Gm, 
4- 54 
4*45 
5- 95 
0935 
5. 60 
36-65 
07 
£{8 
.3 1 
Per ct. 
O. 020 
021 
023 
022 
OI9 
021 
SOLUBILITY OF IRON IN THE} NUTRIENT SOLUTIONS 
An attempt was made to estimate the soluble iron in some of the 
nutrient solutions by filtering the solutions to remove precipitated iron 
and determining iron in the filtrate. Solutions 1 to 9 (used in experi¬ 
ment 4) were analyzed after they had stood various lengths of time both 
with and without plants growing in them. Iron in all the solutions was 
determined by the colorimetric method with potassium sulphocyanate, 
but solutions 1, 2, 4, 5, 7, and 8 without the growth of plants were also 
analyzed by the method of Stokes and Cain. Practically the same re¬ 
sults were obtained by the two methods. The results are shown in 
Table XII. Figures for iron in the solutions without plants are the 
averages of two or more determinations, while the figures for iron in solu¬ 
tions in which plants had grown represent single determinations. The 
results for solution 5 without plants are not trustworthy, as this solution 
could not be filtered absolutely clear by any device the writers considered 
permissible to employ. 
In a comparison of the growth of plants in the different solutions with 
the amount of iron in the filtered solutions, almost as many discrepancies 
as agreements are apparent. One striking discrepancy is the small 
amount of iron in the filtrate of No. 3 and the good growth of plants in 
this solution. Repeated analyses of the precipitate left on the filter 
