Effects Of Different Farmland Environmental Conditions On Soil N₂O Emissions From Nitrifying Inhibitory Bacteria

N₂O,as one of the main greenhouse gases,has a temperature increase effect of 296 times that of CO₂.25%of the N₂O in the atmosphere comes from farmland soil.Therefore,it is of great significance to find ways to reduce N₂O emissions and apply them to farmland soil for the development of ecological farming.This study was carried outbased on microbiological ecology principle,and two strains with inhibitory effects on soil N₂O emissions were isolated.The indoor stationary test was used to simulate the farmland environment to explore the effects of farmland soils with different conditions on nitrification inhibitors to reduce N₂O emissions.The effects of nitrification-inhibiting bacteria on soil nitrification and denitrification bacteria under different conditions were studied using real-time fluorescence quantitative PCR technology,and the activity of nitrification-inhibiting bacteria under different environmental conditions was studied to provide theoretical basis for practical applications.The main results are as follows:?1?The strains that were initially isolated in the laboratory were tested for their effect on suppressing N₂O emissions through an indoor standing test,and the strains with the best emission reduction effects were screened:actinomyces A23 and fungi F14.When the bacterial concentration of strains A23 and F14 is 10⁷cfu·g^-1,the effect of inhibiting N₂O emission is significant?p _A=0.002,p _F=0.000,<0.05?,compared with the control,the N₂O emissions were reduced by 33.77%and 26.26%.?2?A study on the suitable conditions for the cultivation of strains A23 and F14 found that the two strains live in a relatively wide range of environments.The strains A23 and F14can survive in the environment of 10-40?and p H=4-11.The optimal growth temperature of strain A23 is 30-35?,and the optimal growth temperature of F14 is about 30-35?.The suitable p H environments for A23 and F14 growth are 8-9 and 7,which are all weakly alkaline environments.The optimal rotation speed of strain A23 is about 140 r·min^-1.The number of F14 colonies increased within a certain range(<160 r·min^-1)with the increase of the rotation speed.?3?Compared with the control treatment with only A23,F14 bacterial solution,corn straw mulch can reduce N₂O emissions by 6.5%,which can promote the reduction of nitrification inhibitors.When covered with peanut straw,the N₂O emission increased by5.44%compared to the A23 control treatment,and decreased by 1.57%compared to the control treatment of the strain F14.Covering rice straw would reduce the emission reduction of strain A23 by 9.12%,and the effect on strain F14 would be negligible?increased by0.52%?.?4?Studying the effects of adding root exudates from different crops on nitrification-reducing bacteria to reduce N₂O emissions,when the concentration of added root exudates increased,the reduction effect of nitrification-inhibiting bacteria on N₂O weakened.The addition of peanut root exudates promoted the N₂O emission reduction effect.Compared with the control treatment of fungus F14,the emission reduction effect was significant?p=0.001<0.05?,reaching more than 25%,and the emission reduction effect was less than12%compared with the control treatment of strain A23.The addition of corn root exudates had no significant effect on the reduction of nitrification inhibitor N₂O emissions?p>0.05?.When the concentration of added corn root exudates increased,the soil N₂O emissions were significantly higher than the control treatment,which could increase the N₂O emissions by2.63%.?5?After extracting test soil samples and performing real-time quantitative PCR,it was found that the nitro gene copy number per gram of dry soil in each treated soil sample was generally 1-2 orders of magnitude lower than that of nir K gene.Corn straw mulching treatment can increase the number of nitrifying bacteria and nir K denitrifying bacteria in soil.The addition of corn root exudates can increase the number of nir K denitrifying bacteria in the soil and nitrifying bacteria in the soil treated with F14,reduce the amount of Nitrobacter in A23 treated soil.Adding peanut root exudates can generally increase the number of nitrifying bacteria in the soil and reduce the number of nir K denitrifying bacteria in the soil.Therefore,different farmland conditions can affect the production rate and emission of soil N₂O by affecting the number of microorganisms such as nitrifying bacteria and denitrifying bacteria in the soil,thereby affecting the N₂O emission reduction effect of nitrification inhibitory bacteria.The isolated nitrifying inhibitory bacteria has good emission reduction effects and a wide range of survival.It can reduce soil N₂O emissions under conditions such as covering corn stalks and growing peanuts,so it can be applied to actual agricultural production.