Modeling Ammonia Volatilization from Biosolids Applied to Semiarid Rangeland
1997
Harmel, R. D. | Zartman, R. E. | Mouron, C. | Wester, D. B. | Sosebee, R. E.
One fate of N from land-applied biosolids is NH₃ volatilization. This study was conducted to: (i) quantify NH₃ volatilization from anaerobically digested, dewatered biosolids; and (ii) develop equations to predict volatilization losses. Ammonia was collected under natural field conditions with semi-open, dynamic collection systems. Volatilization was measured using a phenol-nitroprusside method for 210 h following biosolid applications of 0.0, 6.7, and 17.9 dry Mg ha⁻¹. Volatilization studies using two soils (a Ustollic Calciorthid and a Ustollic Haplargid) with similar chemical properties but with different surface gravel contents were conducted under hot (20–36°C), intermediate (6–23°C), and cool (−4–14°C) temperature regimes. Volatilization followed a diurnal fluctuating pattern for both the hot and intermediate temperature regime trials and was significantly reduced 3 d after application for all trials. Cumulative volatilization losses ranged from 11.5 kg NH₃-N ha⁻¹ in the cool-season trial for the 6.7 dry Mg ha⁻¹ application rate to 35.5 kg NH₃-N ha⁻¹ in the hot-season trial for the 17.9 dry Mg ha⁻¹ rate. The influence of gravel content on NH₃ volatilization was not statistically significant (P = 0.01). Empirical equations were developed to predict volatilization losses as a function of site- and season-specific potential evapotranspiration, biosolid NH₃-N content, application rate, and time after application. The prediction equations for NH₃ volatilization from applied biosolids as affected by temperature had a range of r² values of 0.90 to 0.97.
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