| In recent years,China’s vegetable cultivation has developed rapidly.The cultivated area of vegetables has increased year by year,with the characteristics of high level of water and fertilizer inputs.Vegetable field always suffers from soil degeneration,high greenhouse gas&reactive nitrogen emissions and low nitrogen use efficiency.In addition to the substantial direct releases from croplands,indirect releases during the manufacture and transport of various agricultural materials contribute to the Nr and GHGs during intensive cultivation with high inputs.Therefore,life-cycle assessment(C footprint and Nr footprint)is necessary and widely accepted concept for Nr releases and GHG emissions,which can accurately locate the key emission hotspots in the production process and provide a basis for the development of emission reduction strategies.In addition,from the perspective of emission reduction strategies,partially substituting inorganic fertilizer with organic fertilizer is suggested as one possible strategy to alleviate GHG and Nr pollution.Meanwhile,vegetables are mainly produced as commercial crops,farmers’ net economic benefits and environmental damage costs should be considered for sustainable development.However,few environmental and economic assessments have been implemented that involved in both the C footprint and Nr footprint measurement for intensive vegetable production.Therefore,five fertilization treatments were established at an equal N level(SN:single inorganic fertilization;SM:single organic fertilization;mixing organic and inorganic N fertilizer at the ratio of 1:2(M1N2),1:1(M1N1)and 2:1(M2N1))and a CK as control.These treatments were selected to measure their field crop productivity(vegetable yield,N uptake,NUE).Nr losses(NOx emission,NH3 volatilization,N runoff,N leaching),SOC sequestration and GHG(N2O)emissions from intensive vegetable rotation in southeastern China.We hypothesize that the appropriate substitute fertilization strategies would improve crop productivity and mitigate Nr losses and GHG emissions simultaneously.The main results are as follows:1.During the observation period,the application of nitrogen fertilizer significantly increased the vegetable yield from 19.3 to 51.4%(p<0.05),The M1N1 treatment produced better vegetable yields at 392.7 t ha-1 than other treatment.Compared with SN treatment,the vegetable yield and agronomic nitrogen fertilizer use efficiency of SM treatment were significantly reduced by 17.7%and 52.6%(p<0.05).The vegetable yield and agronomic nitrogen fertilizer use efficiency of M1N1 treatment significantly increased by 4.5%and 24.3%(p<0.05),there was no significant difference in vegetable yield and agronomic nitrogen fertilizer use efficiency between M1N2 and M2N1 treatment and SN treatment.2.During the observation period,the δSOC varied from-0.32 to 0.87 t C ha-1 under different treatments,with the SM treatment exhibiting a higher δSOC than that of the SN treatment.Compared with SN treatment,organic-applied treatments significantly increased the δSOC by 208.7～478.3%(p<0.05)and the value increased with increasing organic fertilizer application ratios.The application of nitrogen fertilizer significantly increased the cumulative N2O emissions(166.0～466.4%).Compared with SN treatment,the three substitute treatments significantly reduced the cumulative emissions of N2O by 27.3～40.3%.The carbon footprint of all treatments ranged from 0.94 to 1.67 kg CO2-eq kg-1 vegetable.Nitrogen fertilizer production is the primary GHG emission factor(30.2～52.4%).Nitrogen application significantly increased the carbon footprint by 46.4～77.1%(p<0.05).Compared with the SN and SM treatments,the three substitute treatments reduced the carbon footprint by 8.7 to 17.3%,but there was no significant difference between them.3.Compared with SN treatment,the three substitute treatments significantly reduced N2O cumulative emissions(27.3～40.3%),NO cumulative emissions(39.8～51.3%),NH3 volatilization(17.8～22.2%),nitrogen runoff(34.2～44.8%)and nitrogen leaching losses(29.7～35.3%).The foreground interface Nr footprint ranges from 0.92 to 31.53 g N kg-1 vegetables.In the SN treatment,the production of N fertilizer is a hotspot in the foreground Nr footprint(58.8%).In the organic-applied treatments,the production of organic fertilizer is a hotspot in the foreground Nr footprint(87.5～98.0%).The field interface Nr footprint ranged from 0.37 to 10.33 g N kg-1 vegetables.Nitrogen leaching is a major contributor to the loss of Nr in the field(40.5～45.9%).Compared with SN treatment,the three substitute treatments significantly reduced the field interface Nr footprint by 29.3～38.4%.The total Nr footprint of various fertilization treatments ranged from 11.87 to 41.23 g N kg-1 vegetable.The total Nr footprint of the three substitute treatments were 43.9-101.4%higher than that of SN treatment,which required sufficient attention for organic fertilizer compost pollution.4.The annual GHG emission for the treatment of intensive vegetable production range from 12.25 to 29.71 t CO2-eq ha-1,the annual Nr emission range from 16.73 to 637.52 kg N ha-1,and the annual NEEB range from 28.1 to 411.9 million ha-1,the annual environmental damage cost ranges from 0.25 to 2.01 million.In CK and SN treatment,greenhouse gas emissions are the main contributors to EDC(59.6～85.3%).In the organic-applied treatments,Nr loss in the foreground interface is the main contributor of EDC(49.9～72.3%),and greenhouse gas emissions are the secondary contributors(18.0～35.3%).Compared with SN treatment,the three substitute treatments increased EDC(52.7～116.4%),decreased CO2-NEEB(7.5～10.8%)and improved Nr-NEEB(45.5～103.6%).The NEEB of M1N1 treatment has significantly increased by 11,300 ￥ ha-1 yr-1,which is suitable for further promotion. |
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