May 19.1933 Nitrogenous Fertilizers Influencing Chlorosis in Rice 639 
of that salt furnished, it seems possible that the basic residues of the 
nitrates were primarily the cause of the chlorosis and that the alka¬ 
linity of the soil was a secondary factor. 
The reaction of the soil in which the plant roots are in contact with 
the insoluble supply of iron is shown to be of less significance in deter¬ 
mining the availability of iron for the plant than are the effects of the 
products rejected by the plant roots. 
Chlorosis of rice grown on the soil used was especially severe in young 
plants, and plants which were not too seriously affected showed a tend¬ 
ency to recover as they approached maturity. This phenomenon of 
recovery was coincident with a decrease in the rate of absorption of 
nitrogenous compounds, a fact which substantiates the evidence that 
the nitrate fertilizers were causative of the chlorotic condition, although 
it is possible that an increase in the elimination of carbon dioxid from the 
roots had some influence in aiding the plant to recover its normal color 
by making more iron available in the soil. 
The observation that nitrates are less suitable than ammonium salts 
for the fertilization of young rice plants may be based on the influence 
on the plants at the period of greatest absorption of nitrogen of the 
unassimilated residues of the fertilizer used rather than on the inferiority 
of nitric nitrogen as a nutrient. It seems probable also that the injury 
which has heretofore been ascribed to the toxic effect of the nitrites, 
derived from nitrates by reduction, was but a manifestation of chlorosis 
which was caused by the action of the basic residues of the nitrate salts 
used as nutrients. 
The nitrogen of calcium nitrate may be suitable equally with that of 
ammonium sulphate in the physiological processes of the rice plant when 
it is used under cultural conditions in which the reaction of the unassimi¬ 
lated residue of the nitrate does not interfere with the absorption and 
utilization of iron. 
LITERATURE CITED 
(1) Clark, William Mansfield, and Lubs, Herbert A. 
1917. TH® COLORIMETRIC DETERMINATION OR HYDROGEN ION CONCENTRATION 
AND ITS APPLICATIONS IN BACTEMOLOGY. In JoiU*. Bact., V. 2, p. I-34, 
109-136, 191-236, 9 fig. (i fold.) References, p. 233-236. 
(2) Crone, G. von der. 
1904. ERGEBNISSE von UNTERSUCHUNGEN UBER DIE WIRKUNG DER PHOS- 
PHORSAURE AUR DIE hOhere prlanze und eine neue nahrlCsung. 
46 p. Bonn. Inang. Diss. Bibliographical footnotes. 
(3) Daikuhara, G., and Imaseki, T. 
1907. ON THE BEHAVIOR OR NITRATE IN PADDY SOILS. In Bul. Imp. Cent. 
Agr. Hxp. Sta. Japan, v. i, no. 2, p. 7-36, pi. 17-18. 
(4) Espino, Rafael B. 
1920. SOME ASPECTS OR THE SALT REQUIREMENTS OR YOUNG RICE PLANTS, 
In Philippine Jour. Sci., v. 16, p. 455-525, 9 fig., i pi. 
(5) Praps, G. S. 
1908. THE production OR ACTIVE NITROGEN IN THE SOIL. Tex. Agr. Exp. Sta. 
Bul. 106, 31 p., illus. 
(6) GilE, P. L. 
191I. RELATION OR CALCAREOUS SOILS TO PINEAPPLE CHLOROSIS. PortO RicO 
Agr. Exp. Sta. Bul. ii, 45 p., 2 pi. (i col.). 
-and Ageton, C. N. 
1914. THE ERRECT OR STRONGLY CALCAREOUS SOILS ON THE GROWTH AND ASH 
COMPOSITION OR CERTAIN PLANTS. Porto Rico Agr. Exp. Sta. Bul. 
16, 45 p., 4 pl- 
(g) - and Carrero, J. O. 
1916. ASSIMILATION OR IRON BY RICE RROM CERTAIN NUTRIENT SOLUTIONS. 
In Jour. Agr. Research, v. 7, p. 503-528. Literatme cited, p. 528. 
