Effects Of Nitrogen Application Rates And Cultivation On Carbon And Nitrogen Footprint Of Winter Wheat-summer Maize System

Under the situation of global warming,water eutrophication and other serious environmental problems,and the proportion of terrestrial ecosystems is prominent,it is particularly important to quantify carbon and nitrogen emissions from farmland ecosystems and find ways to reduce emissions.The North China Plain is the main production base of winter wheat and summer maize,and unreasonable fertilization and inappropriate management patterns have brought serious environmental problems.Taking winter wheat and summer maize positioning experiment in North China Plain as the research object for 8 years,this paper studied the effects of different nitrogen application(N₀?N₁₀₀?N₁₈₀?N₂₅₅55 and N₃₃₀)and different management modes?farmer practice,High yield and high efficiency,Super high yield practice,Super high yield and high efficiency practice?on the yield of winter wheat and summer maize,established a carbon and nitrogen footprint parameter database and evaluation model,quantified the carbon and nitrogen footprint of winter wheat and summer maize under different treatments,and compared the differences between winter wheat and summer maize,between years and winter wheat under different treatments.The economic benefits of summer maize are expected to provide theoretical support for the realization of high yield,energy saving and emission reduction,and high efficiency of crops in this region.The main results are as follows:?1?The yields of winter wheat and Summer Maize treated with N₁₀₀,N₁₈₀,N₂₅₅55 and N₃₃₀30 were higher than those treated with N₀.The average yield increase of winter wheat was 53.7%,86.2%,81.2%and 65.3%,respectively,and that of summer corn was 36.6%,44.3%,36.5%and 31.2%,respectively.Compared with the farmers practice pattern,the yields of winter wheat and summer maize under the three patterns of high yield,high efficiency,high yield and high efficiency all increased in varying degrees.The average yield increase of winter wheat was 11.6%,18.7%and 12.8%,and that of summer corn was14.5%,26.5%and 18.7%,respectively.Except for seasonal winter wheat,winter wheat and summer maize have the highest yield increase in the mode of super high yield practice,and the mode of high yield and high efficiency has the most efficiency.It was concluded that the crop yield was related to the amount of nitrogen applied,at the same time,it was also related to the operation mode of nitrogen fertilizer such as sowing amount and nitrogen fertilizer topdressing period.?2?The carbon footprint of winter wheat and summer maize farmland system showed the rule of N₃₃₀>N₂₅₅>N₁₈₀>N₁₀₀>N₀ under different nitrogen fertilizer treatments,and the carbon footprint of winter wheat season was generally higher than that of summer maize season.The carbon footprint of winter wheat and summer maize per unit area showed the rule of N₃₃₀>N₂₅₅>N₁₈₀>N₁₀₀>N₀ under different nitrogen fertilizer treatments.In summer maize season,N₁₀₀00 treatment was the lowest;under the four different management modes,the high yield and high efficiency patterns was the best,the carbon footprint was the lowest,and the carbon footprint of the high yield mode and the farmer's habitual mode was higher;the carbon footprint of winter wheat per unit area was the highest in the 2017²018 season,and the farmer practice mode was the highest,at 4398 kg ce/hm²?ce:CO₂equal?.?3?According to the composition of carbon footprint,in the experiment of different nitrogen fertilizer dosage,except N₀ treatment,the other four treatments also showed a higher proportion of nitrogen fertilizer application and irrigation power consumption.The proportion of nitrogen fertilizer application and irrigation power consumption was prominent in the experiment of different management modes,and it was winter wheat season>summer maize season;In carbon fixation,winter wheat summer corn season has the highest proportion of SOC produced by straw returning.?4?There are interannual differences in nitrogen footprint.Under different nitrogen fertilizer treatments,nitrogen footprint increased in turn with the increase of nitrogen application.Except for N₀ treatment,nitrogen footprint of winter wheat and summer maize was lower in N₁₀₀00 treatment and N₁₈₀80 treatment,while that of summer maize was the lowest in N₁₀₀00 treatment,and that of two crops was the highest in N₃₃₀30 treatment.Under four management modes,nitrogen footprint of winter wheat and summer maize per unit area and per unit yield was expressed in high yield and high efficiency mode.The winter wheat mean was 116.8 kg N-eq/hm²,17.6 kg N-eq/t,and the summer corn mean was 122.5 kg N-eq/hm² and 12.9 kg N-eq/t.At the lowest level,the pattern of super high yield and the pattern of farmer practice were the highest.?5?According to the composition of nitrogen footprint,the upstream emissions accounted for a small proportion.Ammonia volatilization accounted for the highest proportion in winter wheat season,nitrate leaching contributed the most in summer maize season,and Nitrous Oxide accounted for the least in both crops,were less than 2%.?6?The net income of winter wheat season was lower than that of summer maize season.In different nitrogen fertilizer treatments,winter wheat was treated with N₁₈₀80 in both seasons,summer maize with N₁₈₀80 in 2017 achieved the highest net income,while summer maize with N₁₈₀80 in 2018 achieved the highest yield,but the highest net income was treated with N₁₀₀,so the net income was not absolutely positive correlation with yield.Under four different management modes,except for the high yield and high efficiency mode of summer maize in 2018,the net income of the high yield and high efficiency mode was the highest,with the exception of 14822 yuan/hm²,which was slightly higher than14740 yuan/hm² of the high yield and high efficiency mode.In summary,the winter wheat season was the best in the N₁₈₀80 treatment and high yield and high efficiency model,and the summer maize season was the best in the N₁₀₀00 treatment and high yield and high efficiency model.