Modified Incubation Chamber Set for Measuring Ammonia Volatilization and Nitrogen Recovery.

Accurate measurement of total nitrogenous gas losses from soil or manure samples in the laboratory is very important in estimating greenhouse gas emission potential under different agricultural production systems. Modified manure/soil incubation chamber set up was developed based on the method developed by Parker et. al. (2005). The modification enabled the system to be more air tight and to control the air flow rates through the chambers more precisely.  Nitrogenous gas recover efficiency of this modified system was tested using an ammonium sulphate solution, added with NaOH or MgO to increase the pH to trigger the NH3 gas emissions. Ammonia emissions were measured using 0.5 H2SO4 acid traps at three flow rates (0.3, 0.6 and 1.0 litre per minute) with 3 replicates for each.  Higher flow rate at 1 l/min results best recovery of 97% N, in acid trap (p=0.001). It took 14 days to evaporate 97% of NH3 from ammonium sulfate solution at pH 11 (using NaOH ). Slow flow rates (0.3 and 0.6 l/min) results lower recovery and higher unknown losses (may be due to NH3 getting stuck to the container inner wall or precipitating as MgSO4). NaOH is the better base to increase the pH to 11, than the MgO, in this experiment. These results prove that this modified and improved chamber set up can be effectively utilised to measure/recover nearly 100% of the gaseous emissions from soil or manure incubation studies, leading to more precise emission measurements in future studies.