『Abstract
A study was conducted to determine nitrogen budget and ammonia
volatilization in Japanese paddy fields supplemented with liquid
cattle waste (LCW). A series of four, 2×10 m experimental plots
was established in a paddy field with silty clay soil planted
with forage rice (Oryza sativa L.). In addition to 195
kg N ha-1 of chemical or compost-based basal fertilizer,
LCW was applied as an additional fertilizer at total nitrogen
rates of 0, 255, 255, and 405 kg N ha-1 to the four
plots C195, T450-1, T450-2, and T600, respectively. The mass balance
showed that after application of LCW, 32-39％ of total input nitrogen
was assimilated into aboveground parts of rice plants, 11-15％
leached downward, 2.5-4.0％ was lost via ammonia volatilization,
1.6-5.1％ was retained in roots or was adsorbed onto soil, and
approximately 30-40％ was lost via denitrification. Compared to
animal waste slurries applied to unsaturated soils, nitrogen loss
via ammonia volatilization was relatively lower, probably due
to the dilution effect of floodwater. Nitrogen loss via denitrification
was markedly higher in areas where LCW was applied compared to
areas without LCW application. On the other hand, nitrogen leaching
downwards represented a substantial loss and may be an environmental
concern. However, after LCW application only, the ammonium ion
was detected, at a maximum nitrogen concentration of 11.4 mg L-1.
In this system, therefore, nitrogen has a different fate to that
in animal waste slurries applied to unsaturated soil. In that
situation, the major nitrogen form in leaching water is nitrate
nitrogen, which moves readily into groundwater.
Keywords: Ammonia volatilization; Assimilation; Cattle waste;
Forage rice; Leaching; Nitrogen cycling』
1. Introduction
2. Materials and methods
2.1. Site description and experimental layout
2.2. Ammonia volatilization
2.3. LCW, irrigation water, and leaching water quality analysis
2.4. Analysis of nitrogen content in rice plants and adsorbed
nitrogen in soil
2.5. Statistics
3. Results
3.1. Temperature, pH, and ion concentrations in floodwater
3.2. Variation of NH3 fluxes after LCW application
3.3. Leaching and soil adsorption
3.4. Biomass production and nitrogen budget calculation
4. Discussion
5. Conclusions
Acknowledgements
References