16,6 Espino: Salt Requirements of Young Rice Plants 461 
land rice, Nagaoka used a soil to which a fertilizer without ni- 
trogen was similarly applied in all cases. To the pots of one 
group he added different amounts of sodium nitrate, and to those 
of another group he added different amounts of ammonium sul- 
phate. Some of the pots of each treatment were kept wet, as 
in rice paddies, while in other pots the soil was kept merely 
moist. The results obtained showed that ammonium sulphate 
gave better yields than did sodium nitrate, for both forms of 
rice and for both soil-moisture conditions. The ammonium 
salt was always absorbed to a greater extent than was the ni- 
trate, but the upland variety absorbed more sodium nitrate than 
did the lowland variety. As to the moisture content of the soil, 
both varieties gave good yields in either one of the two moisture 
conditions studied, but the results were better with lowland 
rice in wet soil and with upland rice in merely moist soil. 
The apparent failure of the rice plant to utilize nitric nitrogen 
and its apparent preference for the ammoniacal form were as- 
cribed by Nagaoka to the fact that paddy rice does “not accu- 
mulate a sufficient quantity of sugar in the leaves to convert all 
of the nitric acid absorbed into protein.” The chlorotic appear- 
ance of the plants supplied with nitrogen solely as nitrates 
might be “due to the physiological influence of accumulated ni- 
trates.” Nagaoka pointed out that the soil of pots receiving 
large additions of nitrate gave a slight nitrite reaction, and he 
suggested that denitrification (resulting in the formation of ni- 
trites from nitrates in the soil) might take place in the rice 
paddy through the action of microorganisms, so that the excessive 
amount of nitrites thus formed might poison the plants. 
Daikuhara ® also found that the application of certain ammo- 
nium compounds to the soil was beneficial to rice. He used 
sand cultures to which limestone and magnesium sulphate were 
added in various proportions. He also added sodium nitrate to 
one pot and ammonium sulphate to another. To a third pot 
ammonium nitrate was added. The total yield (grain and 
straw) showed that, under the conditions of the experiment, am- 
monium sulphate was about two and one-half times as beneficial 
as was sodium nitrate, thus confirm’ng the general conclusion 
of Nagaoka. Daikuhara found also that the fertilizer value 
of ammonium nitrate was intermediate between the values of 
ammonium sulphate and sodium nitrate. 
“ Daikuhara, G., On the application of magnesium in the form of mag- 
nesium sulphate for the needs of the rice plant, Bull. Imp. Central Agr. 
Exp. Sta. Japan 1 (1905) 24-29. 
