| The United Nations Intergovernmental Panel on Climate Change has stated that the contribution rate of greenhouse gas emissions to global warming can reach 90%.CO2,N2O and CH4 are the main components of gr eenhouse gases,and the cumulative emissions of the three can reach the total emissions of greenhouse gases.98.2%,of which the stability of N2O leads to its residence time in the atmosphere up to 120 years,far exceeding the residence time of CO2 and CH4 in the atmosphere.N2O emissions caused by agricultural activities in China accounted for 92%of total N2O emissions.The current research on N2O emissions from farmland soils mainly focuses on crops such as wheat,corn and rice.However,there are few reports on N2O emissions from tobacco-growing soils.The annual tobacco planting area in my country exceeds 10 million mu,and the application of organic fertilizers to tobacco fields is a common measure.In this paper,two organic fertilizers,sheep manure and cake manure,were combined with chemical fertilizer nitrogen at a ratio of 1:1 and 3:1 to study the characteristics of soil N2O emission and its main control factors in Luoyang tobacco area,which is a sustainable tobacco production in Luoyang tobacco area.Development provides a basis for reasonable fertilization.The results of the study are as follows:Ⅰ.Characteristics of N2O Emission from dry field tobacco soil1.Fertilization can significantly increase soil N2O emission flux.Under the same nitrogen application rate,the N2O emission flux of 100%inorganic nitrogen treatment is significantly higher than that of organic/inorganic nitrogen combined treatment.On the third day after basal fertilizer was applied,the 100%inorganic nitrogen treatment had a peak emission flux that lasted for 20 days,with a peak value of 42.2 μg/（m2·h）.The combined application of organic/inorganic nitrogen resulted in the peak discharge period of basal fertilizer.The delay was 4 days,the duration was shortened by 11 days,and the peak value dropped by 52.1%.The average N2O emission flux between treatments showed a decreasing trend as the proportion of organic nitrogen in the fertilizer increased,and there was no significant difference between sheep manure organic fertilizer and cake fertilizer.2.The difference in cumulative N2O emissions from dry farming tobacco fields reached a very significant level:100%inorganic nitrogen>50%inorganic nitrogen/50%organic nitrogen>25 inorganic nitrogen/75 organic nitrogen>no fertilization treatment,sheep manure organic fertilizer There is no significant difference between the treatments with cake fertilizer.During the 142 days from basal fertilizer application to the end of tobacco harvest,the cumulative N2O emission of 100%inorganic nitrogen treatment was 0.375kg/hm2.Compared with CK1 treatment,T1（50%inorganic nitrogen/50%cake fertilizer nitrogen）,T2（50%inorganic nitrogen/50%sheep manure nitrogen）,T3（25 inorganic nitrogen/75 cake fertilizer nitrogen）and T4（25 inorganic nitrogen/75 sheep Manure nitrogen）reduced by 11.8%,19.6%,22.9%and 22.5%,respectively.3.Tobacco field N2O emission coefficients differ significantly among treatments.The N2O emission coefficient of 100%inorganic nitrogen treatment is 0.382%,which is 1.34,1.75,2.00 and 1.96 times of T1,T2,T3 and T4,respectively.The test results show that there is no significant difference between sheep manure and cake fertilizer treatments.4.The N2O emission intensity of tobacco-growing soil has a very significant difference between treatments.The combined application of organic/inorganic fertilizer can efifectively reduce the N2O emission intensity.Among them,the 50%organic nitrogen+50%inorganic nitrogen treatment soil N2O emission intensity decreases the most.In this fertilization mode,when the source of organic nitrogen is sheep manure,the N2O emission intensity is the smallest,only 0.1468g/kg,which is 76.3%of the 100%fertilizer nitrogen treatment.Ⅱ.Analysis of main controlling factors of N2O emission from dry field tobacco soilThrough the dynamic simultaneous monitoring of the 0～5cm soil nitrate nitrogen and ammonium nitrogen content and hydrothermal factors in the tobacco field,it was found that the application of nitrogen fertilizers,especially inorganic nitrogen fertilizers,can effectively increase the nitrate nitrogen and ammonium nitrogen content in the soil.During the monitoring period,the soil The fluctuation range of nitrate nitrogen content is 8.7～40.1mg/kg.Compared with CKO（no fertilization）,T1,T2,T3,and T4 treatments,the average nitrate nitrogen content of CK1（100%inorganic nitrogen）increased by 108%,10.3%,and 12.3,respectively.%,31.7%and 32.1%,the differences between treatments reached significant levels;the soil ammonium nitrogen content is 1.74～8.51mg/kg,the average content of CK1 NH4+during the growth period is more significant than CK0,T1,T2,T3 and T4 treatments,respectively Increased by 76.1%,11.1%,21.9%,42.0%and 30.4%;the soil temperature of 0-5cm between different treatments showed regular changes under the influence of spring,summer and autumn,and the soil moisture content fluctuated in the range of 11.43%～22.60%.Multi factor line regression analysis method showed that in Luoyang tobacco area,the standard coefficients of soil ammonium nitrogen,moisture content and nitrate nitrogen in the multiple linear regression equation were 0.504,0.352 and 0.205,respectively（P<0.05）),combined with the principal component analysis,it can be seen that the main factors controlling the N2O emission from soil in Luoyang tobacco fields are the soil NH4+content and moisture content,followed by the soil NO3-content.Ⅲ.Effects of combined application of organic/inorganic nitrogen on the physical and chemical properties of tobacco-growing soil and the growth and development of flue-cured tobacco1.To analyze the soil of flue-cured tobacco at the maturity stage,the test results show that the combined application of organic and inorganic fertilizers increased the content of available nutrients in the soil to a certain extent,and there was no significant difference in soil pH between the test group and the control group;compared with single application of inorganic fertilizer Treatment,T2,T3,T4 soil available phosphorus content significantly increased by 22.5%,14.8%and 18.3%;the available phosphorus content in the test group increased but did not reach a significant level.The total nitrogen content of soil under different fertilization methods was 0.915 g/kg～1.438 g/kg,and there was no significant difference in nitrogen between organic-inorganic combined treatment and single application of chemical fertilizer.Compared with the CK1 treatment,the organic/inorganic combined application treatment increased the soluble organic carbon content of the soil by 29.36%～42.12%.2.The results show that the combined application of 50%organic/50%inorganic fertilizer helps to improve the coordination of the internal chemical components of the flue-cured tobacco.The ratio of sugar to nicotine,sugar to nitrogen and nitrogen to nicotine in different parts of the flue-cured tobacco tends to be in the appropriate range.This fertilization method helps to promote tobacco plant growth and increase the dry matter accumulation rate.According to the establishment of the flue-cured tobacco biomass accumulation rate model,it can be seen that when 50%sheep manure nitrogen and 50%inorganic nitrogen are combined,the peak period of flue-cured tobacco biomass accumulation rate is higher than 100%.Inorganic nitrogen treatment was advanced by about 5 days,and the peak dry matter accumulation rate during the growth period of flue-cured tobacco reached 4.48 g·d-1,which was 18.2%higher than that of 100%inorganic nitrogen treatment.At 90 days after transplanting,root vitality and root absorption area The active absorption area is 140.7μg/（g·h）,179.84m2 and 73.36m2,respectively.In summary,Using sheep manure to replace 50%of inorganic nitrogen is beneficial to promote the soil ecological benefits of Luoyang tobacco fields and the improvement of tobacco chemical quality. |
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