15 
tively small part of it enters the grain. In addition, only a compara- 
tively small portion of the stnnv is really removed from the land, 
it being the practice to leave about one-half of it on the ground at the 
time of harvesting, while the remaining portion is used for bedding, 
etc., a large part of which sooner or later is returned to the soil. 
Furthermore, whenever manure is accessible the Chinese rice growers 
cart large quantities of it onto the lands, thus considerably aug- 
menting the potash supply. In view of these facts, then, it is hardly 
to be supposed that potash fertilizer will be required for many years. 
In the main, therefore, nitrogen fertilizers only are recommended for 
Hawaiian rice lands. 
In this connection the question of the form of nitrogen best suited 
to rice naturally arises. Experimental data have been obtained on 
this subject which permit the drawing of definite conclusions. 
THE FORM OF NITROGEN FOR RICE. 
One of the most generally accepted teachings in all agricultural lit- 
erature, based, however, mainly upon experiments with dry-land 
crops, is that of the high availability of nitrates, it being considered 
that of all the forms of nitrogen nitrate is the most readily taken up 
from the soil and used as food by plants. As a result of the preva- 
lence of this view nitrates have been used for rice in America, and 
indeed sodium nitrate still is recommended at the present time for 
this crop by some authorities. 
It has been known in oriental countries for soma time, however, 
that nitrate is not the most profitable form of nitrogen to apply to 
rice. Xagaoka, 1 in Japan, demonstrated in 1905 the superiority of 
ammonium sulphate in a series of pot experiments. He found that 
while the effects produced by nitrates were variable and discordant 
the yields were greatly increased in every instance by the use of am- 
monium sulphate. As a result of his experiments Nagaoka concluded 
that the value of ammonium sulphate and nitrates stand in the ratio 
of 100 to 10. 
In 1907 Daikuhara and Imaseki 2 also found ammonium sulphate 
to be much more effective for wet-land rice than either sodium nitrate 
alone or a combination of the two forms. The value of nitrate was 
also found to be considerably less when applied in conjunction with 
organic manures. Likewise it has been shown in several of the Prov- 
inces of India that other forms are superior to nitrates. Coleman 
and Ramachandra Rao, 3 for example, pointed out that organic fer- 
tilizers produced a marked stimulation of the growth of rice in 
Mysore, while niter had but little effect. In 1911 the writer 4 pub- 
1 Bui. Col. Agr., Tokyo Imp. T'niv., G (1904), pp. 2S5-334. 
■BuL Imp. Cent. Agr. Expt. Sta. Japan, 1 (1907), No. 2, pp. 7-36. 
•Dept. Agr. Mysore, G^n. Ser. Bui. No. 2, 1912. 
4 Hawaii Sta. Bui. 24. 
