INFLUENCE OF SOME NITROGENOUS FERTILIZERS ON 
THE DEVELOPMENT OF CHLOROSIS IN RICE ' 
By L. G. Wii»US, Chemist, and J. O. CarrKRO, Assistant Chemist, Porto Rico Agri¬ 
cultural Experiment Station 
DEFICIENCY OF IRON AS A CAUSE OF CHLOROSIS 
The chlorosis affecting certain species of green plants when they are 
grown on calcareous soils has been extensively studied by Gile {6y and Gile 
and Carrero (9), who carried on the greater part of their experimental work 
with rice and with pineapples. They offered strong evidence to support 
their opinion that such chlorosis is caused primarily by the precipitation 
of iron in the soil by calcium carbonate and the consequent inability of 
the plant to obtain a sufficient supply of iron for the development of 
chlorophyll. 
Maz^, Ruot, and Lemoigne {16) have recorded that in some of their 
cultures even the small quantity of 0.2 per cent of calcium carbonate 
was sufficient to render certain species of plants chlorotic by depriving 
them of enough iron for the formation of chlorophyll. 
FACTORS GOVERNING THE AVAILABILITY OF IRON 
REACTION OF THE CULTURE MEDIUM 
Gile and Carrero (<?) further showed that in some solution cultures of 
neutral or alkaline reaction rice became chlorotic, and that such condi¬ 
tion was attributable to precipitation of iron as phosphate and hydroxid. 
In their more acid solution, which had a reaction equivalent to a Ph 
of 3.1, these investigators noted an apparently higher degree of avail¬ 
ability of all forms of iron used. In all these solutions nitrogen was 
supplied in the form of nitrates. 
Working more recently with wheat in sand culture with nitrogen fur¬ 
nished in the form of calcium nitrate, McCall and Haag {18) have shown 
that solutions having P^ values ranging from 4-D2 to 7.00 produced chlo¬ 
rotic plants, the color of which was not restored by the addition of ferric 
nitrate to the culture. The addition of very small quantities of sul¬ 
phuric acid, however, resulted in marked improvement in the color of 
the plants, which became normal green at harvest time. These investi¬ 
gators were of the opinion that the indirect evidence supported the 
assumption that chlorosis in their less acid cultures was due to lack of 
available iron or to faulty metabolism resulting from immobility of iron 
in the plant, 
SOLUBLE PHOSPHATES 
Factors in addition to the reaction of the culture medium are known 
to influence the development of chlorosis. Crone {2) advanced the 
hypothesis that soluble phosphates in solution cultures caused chlorosis 
of plants. Takeuchi (25), on the other hand, using wheat as a culture 
plant, showed that the chlorosis observed by Crone was probably due to 
the precipitation of iron as a phosphate in the culture medium. Later, 
Sidorine (22), working with corn, offered evidence to show that chlorosis. 
* Accepted for publication July ii, 19 ^ 9 . 
* Reference is made by number (italic) to “Literature cited,” p. 639-640. 
(621) 
Journal of Agricultural Research, 
Washington, D, C, 
aeb 
Vol. XXIV, No. 7 
May 19,1933 
Key No. B-18 
