AMMONIA VOLATILIZATION FROM LIQUID HOG MANURE - INFLUENCE OF AERATIONAND TRAPPING SYSTEMS

Measurements of N loss from manures may reflect differences In the typ es of manures and methodologies used. This study's objective was to te st the suitability of 0.32 M H3BO3 and 0.9 M H2SO4 for trapping NH3 vo latilized from liquid hog manure (LHM) under various experimental cond itions. Samples of LHM were incubated for 15 d in containers with aera tion outlets positioned above, at the middle, or at the bottom of the LHM. Lowering the position of the aeration outlet increased both the p H of the LHM and the amount of NH3 volatilized. More NH3 was trapped i n H2SO4 than H3BO3, and the difference in trapping efficiency of the t wo acids increased with their NH3 concentrations. Neither the amount o f NH3 trapped nor the exponential relationship between the NH4+ concen trations of two H3BO3 traps in series was influenced by changing the b ubble 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 H,3BO3 in the Kjeldahl method. Even when using two traps in series, H3BO3 appeared to trap less NH, t han H(2)S0(4). Amending LHM with sucrose lowered the pH of H3BO3 used to trap volatilized NH3, thereby interfering with NH3 determination an d rendering NH3 volatilization. Investigators who use H3BO3 to measure NH3 volatilization in other systems must ensure that similar interfer ences do not occur and that NH3 concentrations do not exceed 0.42 mp N mL(-1).