86 
Journal of Agricultural Research 
Vol. IX, No. 3 
Table XIX .—Iron and nitrogen absorbed by rice in Experiment IX 
Flask No. 
Iron (FeaOs). 
Nitrogen 
(N) in dry 
stalks and 
leaves. 
In dry 
stalks and 
leaves. 
Absorbed 
by 8 
plants. 
Absorbed 
per gram 
of roots. 
1-12 
13-24 
25-36 
. 37-48 
4Qt-6o 
Per cent. 
0. 0400 
. 0229 
. 0223 
.0378 
.0378 
Gm. 
Gm. 
Per cent. 
3. 90 
3 - 90 
3. 80 
3 * 72 
3 - 70 
O. 000899 
. 001370 
• 001635 
. 002266 
O. 00142 
. 00078 
. 00227 
. 00120 
This was one of the preliminary experiments conducted in a study of 
the assimilation of iron by rice from certain nutrient solutions (5). It 
was found that ferrous sulphate, used at this diminishing rate of 0.008, 
0.004, and 0.002 gm. of iron per liter, apparently did not furnish suffi¬ 
cient available iron for an optimum' growth of the plants. Because of 
this insufficiency of iron it was to be expected that plants with half 
their roots in the complete solution would absorb only half as much 
iron as those with all their roots in the complete solution, the former 
having only half as much iron at their disposal as the latter. This would 
doubtless have been the case if the available iron had been a fixed quan¬ 
tity in the solution. Other work showed, however, that most of the 
iron was not present in true solution, that the quantity of iron available 
was probably dependent on the rate at which iron went into solution, 
and that this rate was influenced by the rate at which it was removed 
by the plant. As plants with only half their roots in the complete solu¬ 
tion would absorb iron more quickly than plants with all their roots, 
they might absorb more than half the quantity of iron. 
If plants 13 to 24 are compared with 25 to 36, where the iron was 
added to the neutral nutrient solution, it can be seen that the partial- 
iron plants absorbed 0.66 as much iron as the complete-iron plants and 
absorbed 1.82 times as much per gram of roots. If we compare plants 
37 to 48 with 49 to 60, where the iron was added to the acid nutrient 
solution, it can be seen that the partial-iron plants absorbed 0.72 as 
much iron as the complete-iron plants and absorbed 1.89 times as much 
iron per gram of roots. 1 The ratio of roots to tops varied little between 
the partial- and complete-iron plants in either the acid or the neutral 
solution. The figures for the relative amounts of iron absorbed by the 
partial- and complete-iron plants agree fairly well with similar figures 
for the other nutrients. 2 
1 Small amounts of iron from ferrous sulphate are more available in the acid than in the neutral solution. 
2 There is another source of doubt in this experiment aside from the insufficiency of iron referred to 
above. Both ferrous and ferric iron were doubtless present in the solutions, and the plants probably ab¬ 
sorbed both forms of iron. It is pointed out in another place (5) that there may be a difference in the 
efficiency of these two forms of iron in the plant. At all events, in several experiments ferrous sulphate 
was a less efficient form of iron than ferric compounds. The much higher percentage of iron in the plants 
grown in the acid solution is probably due to a greater absorption of ferrous iron. 
