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- Behavior and Availability of Ammonium in Flooded Soils
Behavior and Availability of Ammonium in Flooded Soils
Dissertation Abstract:
The studies were conducted to determine the native fixed-NH4+ the extent and magnitude of ammonium fization of some Philippine and Thai soils, ammonium volatilization, availability of native ficed-NH+4, and recovery of applied ammonium in a growing lowland rice.
The values of native fixed-NH4+ varied from 5 to 300 ppm of nitrogen. There appeared to have no definite trend in the distribution of fixed-NH4+ with soil depths. The amounts of native fixed-NH4+ were related to the orders of soil. The amounts of fixation of applied ammonium ranged from 3 to 108 ppm of nitrogen. Oven-drying tended to fix more applied ammonium than air-drying.
The average ammonia volatilization ranged from 1.79 percent to 11.06 percent and 0.13 percent to 1.97 percent of applied ammonium without and with rice plant, respectively. The volatization was related to the amounts of exchangeable calcium, initial soil pH, and a standing rice crop caused to decrease the volatilization. Volatilization rate was rapid at first, then slowed down during the second week.
Fixation of applied ammonium at different periods of submergence varied from 0.42 percent to 85.83 percent and 10 percent to 17 percent of applied ammonium without and with a crop, respectively. The fixation decreased with the duration of submergence.
The availability of native fixed-NH4+ ranged from 2 to 8 percent and from 5 to 26 percent without and with rice crop, respectively.
Recovery of applied ammonium by the rice plant ranged from 0.7 to 4.2 percent. The percentages were quite low owing to the immaturity of the plants.