Effects Of Fertigation On N₂O And NO Emissions In Greenhouse Vegetable Fields And The Contribution For Mitigation

In order to maintain higher productivity,excessive fertilization and irrigation in agricultural production have caused serious environmental problems,such as greenhouse and noxious gases emissions（i.e.,N₂O and NO）.Therefore,to ensure sustainable development of agriculture,it is necessary to reduce N₂O and NO emissions by improving water and fertilizer management.In this paper,four treatments,i.e.control（CK）,farmers’practice（FP）,farmers’practice with drip irrigation（FPD）,and optimal fertilization with drip irrigation（OPTD）were conducted in a typical vegetable system in suburbs of Beijing,using the methods of static chanber-gas chromatography and chemiluminescent analyzer,with the aiming to clear about the N₂O and NO emissions characteristics and impact factors in greenhouse vegetable,and analyze the effects of fertigation on water and fertilizer utilizaton and soil N₂O and NO emissions.The results showed that:（1）Fertilization and irrigation were the major factors inducing N₂O and NO emission peaks for acertain time,and the N₂O emission peaks lasted for 10 days after basic fertilization,and for 3 to 5 days after additional fertilization.The peak of N₂O fluxes can reach 16.09 mg·N·m^-2·h^-1 after flooding irrigation.NO emissions peak appeared primarily after irrigation and fertilization,and may postponed for 2⁵ days after irrigation.Fertilizer was the main factor causing NO emissions.（2）Soil moisture,soil temperature and soil inorganic nitrogen were the main factors affecting N₂O emissions.Under the condition of fertigation,N₂O emission was significantly related to soil temperature in each planting season（p<0.05）.Soil moisture also had a significant impact on N₂O emission during cucumber growth seasons（p<0.05）.The variation trend of N₂O emissions was consistent with the change of soil inorganic nitrogen.However,soil temperature and moisture were not the main factors driving NO emissions in this observation period.（3）Fertigation can significantly reduce N₂O and NO emissions.The accumulative N₂O emissions in FPD and FP treatment ranged from 11.02 to 21.01 kg·N·hm^-2,and 16.72 to 29.77 kg·N·hm^-2,respectively.Compared with conventional irrigation,fertigation can reduce seasonal N₂O emissions by29.41%³5.12%.Optimal fertilization with drip irrigation could significantly reduce N₂O emissions by32.63%⁵1.45%.Meanwhile,the cumulative NO emissions can be effectively mitigated by 15.30%when reducing the N application rate by 40%under the condition of drip irrigation.It can be seen that application of fertigation can significantly reduce N₂O emissions while ensuring yield.However,NO emissions were pretty less than N₂O emissions,fertigation can reduce NO emissions by 6.80%compared to flooding irrigation.（4）There was a significant correlation between water and fertilizer use officiency and N₂O emission intensity.Fertigation increased the water and fertilizer use efficiency,thus reducing N₂O emissions.The fertigation can increase cucumber yield by 2.00%to 14.61%than conventional fertilization,and the water and fertilizer use officiency by 14.62%to 43.54%and 2.00%to 27.14%,respectively.It indicated that the increase of water and fertilizer utilization efficiency had an important effect on N₂O emission reduction.In conclusion,fertigation can significantly reduce N₂O and NO emissions,and improve the water and fertilizer utilization effects while maintaining vegetable yields.The results could provide not only basic data and technical reserve for optimizing water and fertilizer management in vegetable fields,but also a theoretical basis for the policy-making on N₂O and NO emission mitigation measures.