May 19, 1923 
Nitrogenous Fertilizers Influencing Chlorosis in Rice 635 
In this test the rice that was fertilized with calcium nitrate was more 
or less chlorotic in all pots until after the first cutting was made. The* 
plants that were furnished with ammonium nitrate were chlorotic for 
only the first few days of their grov/th. Plants that were fertilized with 
ammonium sulphate were not chlorotic at any stage of development. 
There was a wide variation in the degree of chlorosis of the different 
plants which had been made chlorotic as a result of fertilizer treatment. 
It was therefore found advisable in the first cutting to include with the 
two pots treated with calcium nitrate a third pot in which the chlorosis 
was so severe that it was doubtful whether the plants would survive for 
a later cutting. At the time of the second cutting some of the plants in 
pots No. 4 and 5, which had been given calcium nitrate, had become 
green, and the others were only partly chlorotic. The plants from each 
of these pots were therefore divided according to their color into two 
samples to be weighed an<T analyzed. 
As was found in experiment I, ammonia nitrogen was apparently 
almost completely absorbed by the soil very soon after the addition of 
the ammonium sulphate, and nitrites were not found in significant 
quantities at any time. This may have been due to the nonproduction 
of the latter form of nitrogen, to its rapid assimilation by the plants, or 
to conversion to other forms of such amounts as were produced. 
The concentration of nitrates in the soil water had decreased consid¬ 
erably at the time of the first cutting, and when the second samples were 
taken the waters were nearly free of nitrates —a phenomenon which was 
coincident with the recovery of a majority of the plants from chlorosis and 
which may have been indirectly a contributory factor influencing recovery. 
In regard to the average yield of mature heads per pot, the pots which 
were treated with calcium nitrate were practically equal to those which 
received ammonium sulphate, while the yield from the pots to v/hich 
, ammonium nitrate had been added was somewhat lower than that made 
by the others. The wide differences in yields from individual pots that 
were treated with ammonium nitrate may indicate, however, that the 
yield was influenced by some detrimental factors which did not cause 
other visible symptoms of injury; and it is possible that the relative 
inefficiency of the form of nitrogen used was not the cause of the low 
average yield. 
The basis of selection of the pots in which the soil had been treated with 
calcium nitrate and from which the plants were to be harvested at 
maturity is open to criticism. It is thought, however, that the three pots 
in which the plants made rapid and complete recovery from chlorosis are 
comparable with the same number of pots of any other treatment, and 
that they are, for purposes of determining the influence of the fertilizer 
on the yield, more truly representative of the treatment than would have 
been an average which included some chlorotic plants. With this point 
in view it is evident that, under the conditions of this experiment, the 
nitrates, as represented by calcium nitrate, served for the nutrition of 
the rice plant as suitably as did ammonium sulphate when the factors 
causing chlorosis were inoperative. 
ANALYTICAL DATA 
As to the cause of chlorosis in the series of pots which received calcium 
nitrate, some interesting analytical data showing some of the differences 
between plants of the first and second cutting in experiment III and 
between green and chlorotic plants of the same cutting are given in 
Table IV. 
