Evaluation of Selected Processes Controlling Nitrogen Loss in a Flooded Soil
1980
Reddy, K. R. | Patrick, W. H. | Phillips, R. E.
The roles of NH₄-N diffusion, NH₄-N oxidation, NO₃-N diffusion, and NO₃-N reduction in controlling N loss from continuously flooded soil were evaluated in independent experiments. Applied NH₄-N moved from zones of high NH₄-N concentration to the zones of low NH₄-N concentration. The average diffusion coefficient (D) for NH₄-N in flooded soil ranged from 0.059 to 0.216 cm² day⁻¹ for different soils. Diffusion coefficients were influenced by soil type and soil-water content. Rate of NH₄-N oxidation in the aerobic layer of flooded soil range from 1.2 to 3.5 µg g⁻¹ day⁻¹ in different soils. Nitrate diffusion into the anaerobic soil layer ranged from 0.96 to 1.91 cm² day⁻¹, whereas NO₃-N reduction rates were 0.32 to 0.52 day⁻¹. The slow rate of NH₄-N diffusion from the anaerobic soil layer to the aerobic soil layer and the slow rate of NH₄-N oxidation in the aerobic soil layer indicate that these two processes are limiting steps in controlling N loss. Nitrate diffusion into the anaerobic soil layer and NO₃-N reduction in the anaerobic soil layer were found to proceed at a faster rate and are not likely to limit N loss from flooded soil.
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