632 
Journal of A gricultural Research 
Vol. XXIV, No. 7 
EXPERIMENT III.^THE COMPARATIVE EFFICIENCY OF NITRATE 
AND AMMONIUM NITROGEN AS FERTILIZER FOR RICE WHEN THE 
INTERFERENCE OF CHLOROSIS IS DIMINISHED 
In experiment I it was found (i) that the application of sodium nitrate 
to rice in a calcareous soil was attended by a chlorotic condition of the 
rice plant, and (2) that spraying with a solution of an iron salt was only 
partly effective in remedying the condition. 
To determine, then, the comparative suitability of nitrate and ammo¬ 
nium nitrogen on this soil, an attempt was made to take advantage of 
certain individual rice plants whjich are less affected by the conditions 
causing chlorosis than are others, and also of a characteristic of the 
variety of rice used, the characteristic being that the rice tillers freely 
and produces culms and yields which are not closely dependent upon the 
maintenance of a definite number of plants of uniform size per unit area. 
Eighteen pots were prepared and treatments were added in the same 
manner as they were in the previous tests, 2 gm. of nitrogen being fur¬ 
nished each pot in the forms of calcium nitrate, and ammonium sulphate. 
Calcium nitrate was chosen in preference to sodium nitrate to minimize, 
'if possible, the intensity of the effect of the basic ion. Ammonium nitrate 
was used as a physiologically neutral form of nitrogen intermediate 
between the nitrates with basic residues and ammonium sulphate with 
acidic residues. 
Potassium sulphate in sufficient quantities to furnish 2 gm. KjO and 
phosphoric acid in quantities to supply 4 gm. P2O5 were added to each pot. 
Nitrogen treatments were replicated in six pots so that cuttings might 
be made at different stages of plant growth. It was planned to make the 
first cutting of plants representing each treatment at about the time that 
the plants which had received calcium nitrate were showing evidence of 
recovery from chlorosis, selecting for samples of the rice grown with 
calcium nitrate the plants in those pots in which chlorosis was most 
severe, so that those which were least affected and which might make 
the quickest recovery could be allowed to mature to afford a better 
comparison of the yields as governed by the efficiency of the different 
forms of nitrogen. 
The second cutting was made when the heads were beginning to emerge 
from the boot, at which time all the plants in the test showed a remarkable 
uniformity in degree of maturity. 
Seeding was made as in the other experiments. Ten seedlings were 
allowed to remain in each pot until the pots which had received calcium 
nitrate could be arranged in the order of their intensity of chlorosis. 
Two pots representing each treatment were then selected to be held for 
the first cutting, 10 plants being allowed to remain in each pot, and 4 
seedlings were removed from each of the other six pots. Table III gives 
the results of the experiment. 
