5:15 PM - 6:30 PM
[AHW22-P27] Effects of different NH4+-N contents on N2O and CO2 emissions from manure compost-amended soil
Keywords:Nitrous oxide , Carbon dioxide, Manure compost, Ammonium nitrogen, Microbial activity
Nitrous oxide (N2O) is a major greenhouse gas that causes global warming and stratospheric ozone depletion. Ammonium nitrogen (NH4+-N) content is considered as a key factor affecting N2O emissions because ammonium oxidation by nitrifying microorganisms is a major process of N2O emissions. Exact effects of NH4+-N on N2O emissions are less examined and even available findings are contradictory. Some studies found strong positive linear correlations between N2O emissions and NH4+-N content, while others stated reductions in N2O emissions with increasing NH4+-N content. Therefore, the present study aimed at investigating effects of different NH4+-N contents on N2O and carbon dioxide (CO2) emissions from manure compost amended soil.
Greenhouse soil was amended with two types of manure composts (cattle compost, CC and mixed compost was of cattle, poultry, and swine manure, MC) on 3% weight basis. The initial NH4+-N contents were adjusted at three levels of 160, 200, and 400 mg kg-1. The samples were aerobically incubated at 70% water holding capacity at 25°C for 42 days. Emissions of N2O and CO2 (gas chromatography) and ammonium and nitrate N contents of soil were measured on days 0, 3, 7, 14, 21, 28, and 42.
The highest cumulative emissions of N2O (200-420 mg kg-1) and CO2 (7-11 g kg-1) were observed in MC amended soils at each NH4+-N level. This is probably due to high total N, low C/N, and high mineral N of MC. The MC amended treatments with 160 mg kg-1 NH4+-N content showed peak emissions on day 7. In all other treatments, N2O emissions peaked on day 3, indicating that the nitrification process was enhanced by the addition of NH4+-N. The cumulative N2O and CO2 emissions in 400 mg kg-1 NH4+-N treatments were lower than those in 200 mg kg-1 NH4+-N treatments despite the addition of compost. Higher NH4+-N content would have suppressed the microbial activity probably due to enhanced osmotic effects. In both control and CC amended treatments, cumulative N2O and CO2 emissions increased with NH4+-N contents from 160 to 200 mg kg-1, whereas they decreased in 400 mg kg-1 NH4+-N treatments. The variation of NO3--N content suggested that the MC amended treatment with 160 mg kg-1 NH4+-N content was subjected to a high denitrifying activity compared to the other treatments. With increasing NH4+-N content, the denitrifying activity seemed to decrease due to high osmotic potential. In conclusion, compost with high total and mineral N and low C/N enhanced N2O and CO2 emissions at each NH4+-N content. More NH4+-N suppressed microbial activities due to osmotic stress, and therefore lower N2O and CO2 emissions were recorded. Soil content of NH4+-N is a key factor in determination of N2O emissions.
Greenhouse soil was amended with two types of manure composts (cattle compost, CC and mixed compost was of cattle, poultry, and swine manure, MC) on 3% weight basis. The initial NH4+-N contents were adjusted at three levels of 160, 200, and 400 mg kg-1. The samples were aerobically incubated at 70% water holding capacity at 25°C for 42 days. Emissions of N2O and CO2 (gas chromatography) and ammonium and nitrate N contents of soil were measured on days 0, 3, 7, 14, 21, 28, and 42.
The highest cumulative emissions of N2O (200-420 mg kg-1) and CO2 (7-11 g kg-1) were observed in MC amended soils at each NH4+-N level. This is probably due to high total N, low C/N, and high mineral N of MC. The MC amended treatments with 160 mg kg-1 NH4+-N content showed peak emissions on day 7. In all other treatments, N2O emissions peaked on day 3, indicating that the nitrification process was enhanced by the addition of NH4+-N. The cumulative N2O and CO2 emissions in 400 mg kg-1 NH4+-N treatments were lower than those in 200 mg kg-1 NH4+-N treatments despite the addition of compost. Higher NH4+-N content would have suppressed the microbial activity probably due to enhanced osmotic effects. In both control and CC amended treatments, cumulative N2O and CO2 emissions increased with NH4+-N contents from 160 to 200 mg kg-1, whereas they decreased in 400 mg kg-1 NH4+-N treatments. The variation of NO3--N content suggested that the MC amended treatment with 160 mg kg-1 NH4+-N content was subjected to a high denitrifying activity compared to the other treatments. With increasing NH4+-N content, the denitrifying activity seemed to decrease due to high osmotic potential. In conclusion, compost with high total and mineral N and low C/N enhanced N2O and CO2 emissions at each NH4+-N content. More NH4+-N suppressed microbial activities due to osmotic stress, and therefore lower N2O and CO2 emissions were recorded. Soil content of NH4+-N is a key factor in determination of N2O emissions.