Vergara - 1976 - Physiological and morphological adaptability of ri

TEMPERATURE AND CIIENHCAL KINETICS OF 1100mm SOILS 255
ofA and Ea were of the order of those [or biochemical reactions. The six soils
studied gave Q“, values of 2 to 3 in the range 25° to 35°C.
Nitrate can persist for weeks in cold. acid submerged stiils. So nitrate fertilizer
can be used in such soils if the ammonium forms are not available.
Ammonification
The greater part of the nitrogen taken up by a rice crop comes from ammonifieation
of soil organic matter. Since ammonification. like other enzyme reactions.
is temperature dependent. temperature should exert a marked influence
on the nitrogen supply to rice.
Shioiri and Tanada (1954) and Mitsui (1960) reported a virtual dotibling of
ammonia production when the temperature of anaerobic incubation was raised
from 26° to 40°C. Kavcaguehi and Kyuma (1969) and Cho and Ponnamperuma
(1971) have reported similar increases in the range 15° to 40°C. Takai (1952)
found that raising the temperature from 30° to 40°C. even after 52 days submergenee.
markedly increased ammonifieation.
In an anaerobic incubation study of four soils. IRRI workers (IRRI. 19B)
ObSCfVCd that the rate of ammonilieation was lowest at 15°C and highest at 45°C
in all soils except Luisiana clay. in which the rate at 45°C was less than that at
35°C (Fig. 5). Ammonifieation followed first-order kinetics, and the variation
NH 3- n £09m 1
4G0
cAsisuRAN cur tom
45 °c .---" \__o
"
ss°c
PlLA CLAY LDA M
Incubation (wk)
5.
Influence of temperature on the kinetics of ammonifieation in flooded soils.