Effects Of Acidification And Ameliorants On Nitrous Oxide Emission In Black Soil

In recent years, one of the main forms of black soil degradation is soil acidification, which influences soil habitats, nitrous oxide (N2O) production process as well as emissions. The soil for the laboratory experiment was collected from the Key Observation Station of the Harbin Black Soil Ecology of Harbin city, Heilongjiang province, China. The aim of this paper is to investigate the effects of soil pH and soil ameliorants on the characteristic of N transformation and the process of N2O and CO2 production through the incubation experiment. Simultaneously, the yield of bean was researched by field experiment.Soil pH had a strong impact on N2O emission with different N treatments and the highest N2O flux appeared at the beginning of incubation. The soil N2O emission increased with the soil pH increasing fertilized with CK and NH4+-N. The cumulative CO2 emission was considerably lower in acidic soil than that of soil with higher pH, which was attributed to the sharp reduction of soil respiration in soil with lower pH. The maximum N2O and CO2 emission rates occurred at soil (pH: 8.55) applied with NO3--N and NH4+-N, respectively. However, the highest N2O emission fertilized with NH4+-N appeared at soil (pH: 6.90). This indicated that denitrification played a dominating role in alkaline soil while nitrification did in neutral soil. The results also showed NH4+-N had a stronger capability of increasing carbon availability. The net changes of SON and NO3--N were dramatically decreased in most case, especially in CK treatment. However, the net changes of NH4+-N were significantly increased in the treatment fertilized with NO3--N. This demonstrated that heterotrophic microbes played an important part in N2O emission and contributed to the accumulation of NO2--N.The laboratory experiment results showed that the ameliorants critically increased the original soil pH by 1.6-2.5 units. The N fertilizer and C resource inputs to soil remarkably increased the outputs of CO2 and N2O emissions and the CO2 emissions shared the similar flux tendency with the N2O emissions. The maximum N2O and CO2 emission rates occurred at soil ameliorated by lime applied with NO3--N (pH: 7.52) and soil ameliorated by ash applied with NH4+-N (pH: 6.11), respectively. This implied that NO3--N was favorable to N2O emissions while NH4+-N resulted in much CO2 evolution.Regretfully, the ameliorants had no significant influence on incresing field soil pH. Although ash had a positive effect in the weight of 100-grain, the ameliorants didn't improved the yield. What's more, the lime would not act as a mitigation of N2O emissions and would lead soil compaction. Therefore, in view of economic efficiency, environmental protection and the maintenance of soil fertility, the application of plant ash was a more effective improvement measure.