460 
Philippine Journal of Science 
1920 
times, using the same salts but varying the amounts. He con- 
cluded that paddy rice in the early stages of its development 
grew better in a nutrient medium supplied with ammoniacal 
nitrogen than in one supplied with nitrate nitrogen, while during 
the later stages of development the nitrate proved to be a better 
source of nitrogen than was the ammonium salt. He also tried 
culture solutions containing the other necessary elements and 
having the ammonium salt and the nitrate both present at once, 
and found that the combination of these forms of nitrogen 
gave better growth than did either form alone. 
The beneficial effect of ammonium sulphate, as well as the 
unsuitability of nitrates as sources of nitrogen for rice, were 
also observed by Nagaoka,® who carried out a series of rather 
extensive pot and plot experiments with upland and lowland 
varieties of rice grown to maturity. He began his cultures 
with plants about 42 days old, so that the plants had passed be- 
yond the first stages of growth before they were tested. By 
means of pot cultures with soil he compared the growth and the 
yield of a lowland rice supplied wdth different amounts of ammo- 
nium sulphate with those of the same variety supplied, separate- 
ly, with one of the salts, sodium nitrate, potassium nitrate, cal- 
cium nitrate, barium nitrate, strontium nitrate, and magnesium 
nitrate. He found that plants grown in the media supplying 
nitrogen in the form of ammonium sulphate alone were green and 
produced much tillering (branching at the base of the stem), 
while plants “fed” with one of the nitrates were yellowish and 
produced but little tillering. The six nitrates tested were about 
alike in this effect. Nagaoka observed, however, that the seed 
ripened ten days earlier when the plants had been supplied with 
a nitrate than when they had been supplied with the ammonium 
salt. 
The field-plot experiments of Nagaoka were planned to study 
the fertilizer values of sodium nitrate and ammonium sulphate. 
In these experiments he applied one or the other of the two 
salts to the soil. The fertilizer application was made before 
planting and also at intervals during the growth of the plants. 
Lowland rice was again used and, as in his previous pot experi- 
ments, the yield obtained showed that ammonium sulphate was 
about two and one-half times as good as sodium nitrate in this 
respect. 
In another set of pot experiments, with upland as well as low- 
’ Nagaoka, M., On the behavior of the rice plants to nitrates and am- 
monium salts. Bull. Coll. Agr. Imp. Univ. Tokyo 6 (1904) 285-334. 
