Nitrogen Efficiency of Urea Amended With Inhibitors and Cations Applied to Rice
Urea, the major source of nitrogen (N), is subjected to extensive gaseous N losses to the atmosphere. Ammonia (NH3)volatilisation and denitrification losses are important mechanisms for N losses from urea and are causes of poor fertilizer use efficiency by lowland rice. The study was undertaken...
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| Format: | Thesis |
| Language: | English English |
| Published: |
1994
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/10339/1/FP_1994_1_A.pdf |
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| Summary: | Urea, the major source of nitrogen (N), is subjected to extensive
gaseous N losses to the atmosphere. Ammonia (NH3)volatilisation and
denitrification losses are important mechanisms for N losses from urea and
are causes of poor fertilizer use efficiency by lowland rice. The study was
undertaken in a series of five experiments to evaluate means of increasing
the efficiency of urea-N under flooded rice soil conditions. A laboratory
incubation experiment of different rice soils was conducted to study the
kinetics and transformations of urea in flooded soils. A greenhouse
experiment was carried out on marine and riverine alluvial soils to evaluate
urea-N efficiency in direct-seeded (DS) rice and transplanted (TP) rice
under similar N management practices using lSN-Iabelled urea. Two
greenhouse and one field studies were conducted to evaluate the
effectiveness of inhibitors and cations on marine and riverine alluvial rice
soils on the efficiency of urea-N using 15N recovery techniques. Urea hydrolysis followed the first-order kinetics and rate constants
ranged from -0.032 to -0.076 ha-1 A lag phase existed in flooded soil
conditions and it varied from 6 to 15 hours. The half-life of urea ranged
from 12 to 26 hours. Urea conversion to NH4 -tN was initially rapid with
about three-fourths being converted within 48 hours of incubation and total
conversion completed within 108 hours. |
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