Modeling ammonia volatilization from loamy sand soil treated with liquid urea
1991
Ismail, K.M. | Wheaton, F.W. | Douglass, L.W. | Potts, W.
Laboratory experiments were conducted to measure amounts of ammonia volatilized from loamy sand soil using an airflow technique. A composite rotatable statistical design was used to define the relationship between ammonia volatilization (Z, kg-N/ha) and temperature (degrees C), soil pH, initial soil moisture content (MC, g water/100 g dry soil), urea application rate (R, 7-N/ha), and urea application depth (D, cm). Soil samples were treated to adjust the sample parameters (i.e., soil pH). Each soil sample was placed in a small container and the containers were placed in an environmentally controlled room. Air was passed through each container and the ammonia volatilized from the soil in the container was trapped in an acid bath. The acid baths were analyzed periodically to determine the amount of ammonia released by the soil. Curves defining the release of ammonia with time were plotted from the results. Using regression techniques, a response surface was developed that defined accumulated ammonia volatilization over a 15-day period as a function of the independent variables. The response surface is defined by the following equation. Ln (Z + 11)= - 0.935 - 0.0417T + 0.570 pH + 0.00367R + 0.178 MC - 0.445D + 0.00154 (T)2 - 0.00739 (MC)2 + 0.0285 (D)2 - 0.000378 (R) (D).
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