628 
Journal of Agricultural Research 
Vol. XXIV, No. 7 
The plants in this series of pots were cut while they were in the boot 
stage, it having been observed that those in soil cultures that had been 
rendered partly chlorotic by means of fertilizer treatment generally 
recovered their normal green color at about this period. 
The results of this test show the influence on the development of 
chlorosis of the form of nitrogen used as a fertilizer and that the nitrate 
furnished was probably active in causing chlorosis, the effect being more 
marked on those pots receiving 2 gm. of nitrogen in that form than it 
was on those pots to which i gm. was applied. It would seem, there¬ 
fore, that the calcareous soil was not the sole causative factor in similar 
cases of chlorosis, although this point has not been definitely established 
by the results obtained from the experiment. 
That chlorosis was due to lack of sufficient iron for chlorophyll forma¬ 
tion was evidenced by the development of a green color where the leaves 
were wet with the solution of ferrous sulphate. The nature of the leaf 
surface, however, was such that it was not possible to wet the entire 
area with the spray solution, and the plants therefore presented a mottled 
appearance. For this reason it is not certain whether the plants that 
were fertilized with sodium nitrate would have made a growth equal 
to that of the plants which received the ammonium sulphate had the 
spraying been more efficient as a remedy for chlorosis. 
Observations made in this test do not show whether the plants which 
received sodium nitrate were chlorotic as a result of the form of nitrogen 
used or on account of the basic residue; whether the chlorosis, if caused 
by the basic residue, was due to the alkalinity of that residue or to the 
specific action of the sodium ion; nor whether there was a depression 
in plant growth additional to that caused by chlorosis. 
A wide variation was observed in the size of the individual plants in 
the same pot and also in the tendency of plants of different sizes to recover 
from chlorosis. Apparently, absolute uniformity of cultural condition 
was not maintained in the experiment and the variations present 
governed the severity of the chlorosis. 
Samples of the soil water for analysis were drawn from the mass of 
the soil by means of a pipette. The method of sampling was not ideal 
for the accurate determination of the composition of the nutrient solu¬ 
tion, but it was chosen because it permitted the least disturbance of the 
plant roots. The determinations of hydrogen-ion concentration that 
were made by the colorimetric method of Clark and Tubs (r) are be¬ 
lieved to be reasonably accurate, but the results showing the concentra¬ 
tion of the different forms of nitrogen are only approximately correct. 
The failure of the analysis to show the presence of appreciable quanti¬ 
ties of ammonia is probably due to the absorption of that nutrient by 
the soil. Such removal of nitrogen from solution did not, it is thought, 
in any way interfere with the ability of the plant to absorb a sufficient 
amount for efficient utilization. 
Evidence of the loss of some nitrogen through denitrification is shown 
by the decrease of nitrate nitrogen in the uncropped pots No. 33 and 35 
during the period in which the plants were growing in the other pots. 
This loss, however, is thought to be of little significance in a comparison 
of the effects of the two forms of nitrogen. 
The small quantity of nitrate nitrogen which accumulated in pots 
No. 34 and 36 as a result of the nitrification of ammonium sulphate may 
indicate that, as Fraps (5), Kelley (jj), and Kellner {12), and others 
have shown, nitrification does not take place in submerged soils; or it 
