| Laboratory experiments were conducted to measure ammonia volatilized from loamy sand soil using an air flow technique. Using the data obtained from this study a model was developed to describe the effect of soil temperature (T, {dollar}spcirc{dollar}C), soil pH (pH), soil moisture content (MC, g water/100 g dry soil), urea application rate (R, kg-N/ha), and application depth (D, cm) on ammonia volatilization (Z, kg-N/ha) as follows: Ln Z = 1.781 + 0.525 T + 0.0954 pH + 0.0029 R {dollar}-{dollar} 1.76 D + 0.00098 MC{dollar}sp2{dollar} + 0.167 pH {dollar}times{dollar} D, R{dollar}sp2{dollar} = 0.92.; The results obtained showed that ammonia loss from soil during the 15 day test period was greatly affected by urea application depth. Increasing application depth from zero (surface application) to 10 cm with the other variables held constant at the center point levels of the statistical design used, decreased ammonia loss from about 50 to zero percent of the nitrogen applied to the soil. Increasing soil temperature from 27.5 to 45{dollar}spcirc{dollar}C, while holding all other variables constant at the center point levels, increased ammonia loss from 3.7 to 23 percent. Ammonia loss was not detectable at 10{dollar}spcirc{dollar}C, when all other variables were held constant at the center point levels. Increasing urea application rate from 40 to 800 kg-N/ha with all other variables held constant at the center point levels, increased ammonia loss from 1.8 to 9.2 percent. However, increasing initial soil moisture content from air dried to 20 percent (dry weight basis) increased ammonia loss from zero to only 1.3 percent. |
