Ammonia Volatilization from Liquid Hog Manure: Influence of Aeration and Trapping Systems

Abstract

AbstractMeasurements of N loss from manures may reflect differences in the types of manures and methodologies used. This study's objective was to test the suitability of 0.32 M H3BO3 and 0.9 M H2SO4 for trapping NH3 volatilized from liquid hog manure (LHM) under various experimental conditions. Samples of LHM were incubated for 15 d in containers with aeration outlets positioned above, at the middle, or at the bottom of the LHM. Lowering the position of the aeration outlet increased both the pH of the LHM and the amount of NH3 volatilized. More NH3 was trapped in H2SO4 than H3BO3, and the difference in trapping efficiency of the two acids increased with their NH3 concentrations. Neither the amount of NH3 trapped nor the exponential relationship between the NH+4 concentrations of two H3BO3 traps in series was influenced by changing the bubble path length through the acid. Regression analysis indicated that >95% trapping efficiency was obtained only when the NH3 concentration of H3BO3 was below 0.42 mg N mL−1, much lower than the 0.9 mg N mL−1 reported to be the limit for using H3BO3 in the Kjeldahl method. Even when using two traps in series, H3BO3 appeared to trap less NH3 than H2SO4. Amending LHM with sucrose lowered the pH of H3BO3 used to trap volatilized NH3, thereby interfering with NH3 determination and rendering H3BO3 unsuitable for determining NH3 volatilization. Investigators who use H3BO3 to measure NH3 volatilization in other systems must ensure that similar interferences do not occur and that NH3 concentrations do not exceed 0.42 mg N mL−1.