NH₃ And N₂O Emissions And Isotopocule Value Of N₂O From Slurry-applied Soil

Utilization of slurry as fertilizer is an important link to realize the combination of cropping systems and livestock production and promote the green and efficient recycling of nutrients.On the one hand,nitrogen in the slurry of livestock can promote the growth of crops and the improvement of soil fertility,and it can also lead to a series of environmental pollution problems such as nitrous oxide（N₂O）,ammonia volatilization（NH3）and nutrient leaching.Therefore,it is one of the main research tasks for the current agricultural green development to clarify the emission characteristics of ammonia,nitrous oxide and other gases after the application of slurry,reveal the influencing factors and mechanism of the gaseous nitrogen loss,and explore the efficient and safe application technology of slurry.In this study,in situ field measurement combined with indoor simulation was used to clarify the effects of surface application（SA）,band application（BA）and other fertilization techniques on NH3 and N₂O emissions after application of slurry and compound fertilizer in summer maize field.The main N₂O production pathway in summer maize soil was explored by using the N₂O stable isotope technology(δ¹⁵N,δ18O and SP value).Through indoor simulation experiments,the reduction effects and mechanisms of nitrification and denitrification inhibitors on NH3 and N₂O emissions from soil applied with slurry were verified,it can provide theoretical and technical support for improving regional atmospheric environment quality,reducing ammonia emissions from agricultural sources and optimizing farmland fertilization.The main results of this study are as follows:（1）Firstly,this study compared the differences between closed incubation system（CIS）and open incubation system（OIS）.Although the emission characteristics of NH3 and N₂O observed in the two incubation systems as well as the effects of the effects of fertilization methods and soil water content on the emission were basically consistent,in contrast,the closed incubation system（CIS）is more suitable for mechanism exploration under different combination of gases due to its good controllability,while the open incubation system is more suitable to combine with field in situ experiments.（2）In the field experiment,the NH3 emission of different treatments were as follows:slurry surface application（SA-S）>slurry band application（BA-S）>compound fertilizer band application（BA-C）,and the N₂O emission were as follows:sluny band application>slurry surface application>compound fertilizer band application.The gaseous nitrogen loss of NH3 and N₂O was significantly different among different treatments.The N loss of SA-S treatment was dominated by NH3-N loss,accounting for 89%of the total gaseous loss,while that of BA-S and BA-C treatment was dominated by N₂O-N loss,accounting for only 6%and 12%of their total gaseous losses.（3）Laboratory inhibitor results showed that nitrification and denitrification inhibitors had little effect on ammonia volatilization and total gaseous nitrogen loss,but significantly reduced N₂O emission（44-67%）in the treatment of incorporation application（IA）.Under the treatment of surface application,the inhibitor had a great effect on ammonia volatilization and gaseous nitrogen loss,and the gaseous losses was in the order of SA-DCD+PC>SA-DCD>SA-CK>SA-PC,in which SA-DCD+PC increased ammonia volatilization by 43.1%,and the application of DCD and PC reduced the emission of N₂O by 44.8%.（4）The isotopcule values of N₂O(¹⁵N^SP and 18O（N₂O/H2O）)in the field were as follows:BA-S>SA-S>CK>BA-C,and the isotopcule values of N₂O in BA-S and SA-S treatments were not significantly different（p>0.05）.The ¹⁵N^SP values of BA-S and SA-S were higher,indicating that the contribution of nitrification or fungal denitrification in slurry treatments to N₂O production was greater than that of BA-C.（5）Isotopic results of inhibitor experiment in laboratory showed that the average values of ¹⁵N^SP and 18O（N₂O/H2O）were in the order of CK>PC>DCD+PC>DCD under two application methods.There were no significant difference in the ¹⁵N^SP and 18O（N₂O/H2O）between PC and CK.In contrast to the SA treatments,the application of inhibitors had significant impacts on the ¹⁵N^SP and 18O（N₂O/H2O）values of N₂O in IA treatments.In conclusion,in terms of fertilization,the nitrogen nutrient loss was the least in the BA-S treatment,and N₂O-N was the dominant contributor to the treatment of BA-S and BA-C,while NH3-N was dominant in SA-S treatment.Compared with SA-S and BA-C,the higher the ¹⁵N^SP value of N₂O in BA-S indicated that nitrification/fungal denitrification contributed more to the N₂O emission.The application of DCD significantly increased the ammonia volatilization,but significantly reduced the N₂O emission,while the application of PC only decreased the N₂O emission during the peak emission period and had minor impact on the ¹⁵N^SP value of N₂O.