Tracing the Transformations of Urea Fertilizer during Leaching
1977
Wagenet, R. J. | Biggar, J. W. | Nielsen, D. R.
The transport and transformation of urea, NH₄⁺, and NO₃⁻ in soil were mathematically described as functions of depth and time, subject to either steady feed or pulse application of N, using relationships derived by assuming diffusion and mass transfer as transport processes and first-order kinetics as a transformational mechanism. The mathematical model was used to study the enzymatic hydrolysis of urea, nitrification, and denitrification in laboratory soil columns. Urea hydrolysis was found to be independent of initial urea concentration and the O₂ concentration of the soil atmosphere. The rate of nitrification under transient N conditions was found to be one order of magnitude greater than the rate of denitrification when there was 20% O₂ in the soil atmosphere. Populations of nitrifiers were found to increase in response to successive applications of N.
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