Effects Of Different Fertilization Levels On Soil Respiration And Carbon Balance Of Summer Maize Of

Soil respiration release of CO₂ plays an important role in global greenhouse gas carbon emissions.Among them,farmland ecosystem CO₂ emissions have been greatly affected by human activities and have been the focus of many researchers.As one of the major grain producing areas in China,the study of soil respiration characteristics and impact mechanisms in the North China Plain is of great significance for comprehensive monitoring of farmland carbon emissions.In this paper,the changes of soil respiration rate of summer maize under different fertilization levels were explored.The experiments were carried out in the National Water-saving Irrigation Engineering Technology Research Center?Beijing?Daxing Experimental Research Base from June to September in 2017-2018,using closed static boxes.The soil respiration of summer maize farmland was monitored.The changes of soil respiration rate and its response to soil surface temperature and humidity were analyzed.The Vant Hoff model,Arrhenius model and Taylor three respiratory models were analyzed.The applicability was verified,and finally the carbon balance of summer maize farmland ecosystem was studied.The main conclusions are as follows.?1?From the daily scale of soil respiration in summer maize farmland during the two years,the daily average changes in each key growth period have obvious daily variation characteristics.The change trend of each fertilization treatment is basically consistent with the daily temperature change characteristics.The peak value of the first increase and then decrease is about 15 o'clock,and the lowest value is around 6 o'clock.With the increase of fertilization amount,soil respiration has more obvious daily average variation characteristics.From the perspective of the whole growth period,the performance was lower in the early stage of re-growth,and the highest value appeared in the 60 th and 63 rd days after sowing,and decreased to the lowest in the late growth period.The soil respiration rate of each treatment showed N3>N2>N1.?2?There was a significant positive correlation between soil respiration rate and soil surface temperature and water content under different fertilization treatments in two years.The soil surface temperature could explain the seasonal variation range of soil respiration rate of 23.1%.⁶9.9%,21.9%⁷0.3%,the soil surface moisture content can explain the seasonal variation range of soil respiration rate of each fertilization treatment is 15.3%⁵0.8%,17.2%⁵5.3%,respectively.The soil surface temperature has an excellent effect on soil respiration.In the soil surface water content,the joint simulation equations can be used to explain that the seasonal variation range of soil respiration in two years is 25.4%⁷9.8% and 27.3%⁸1.6%,respectively.The simulation effect is obviously better than that under single factor condition.The amount of fertilizer applied can increase the sensitivity of soil respiration to temperature.The Q10 values of fertilization treatments in two years were 1.73,2.20,2.29 and 1.68,2.19 and 2.31,respectively.?3?The Vant Hoff breathing model has a good simulation effect on soil respiration without fertilization.In the case of N2 and N3 fertilization,the Taylor breathing model has a better simulation effect on soil respiration.And with the increase of fertilizer application,the breathing model has a better simulation effect on soil respiration.It is applied to the calculation of soil respiration carbon emission during the growth period of summer maize,and its applicability is consistent with the simulation results.?4?After the increase of fertilization amount,the accumulation of summer maize biomass increased significantly.In the early growth stage,the accumulation rate slowed down slowly,slightly slowed in the middle stage,and showed a downward trend in the late growth stage.Fertilization increased the carbon sequestration capacity of CNPP and soil heterotrophic respiration carbon CRH in summer maize farmland ecosystems.However,the net carbon input into the CNEP was not significant when the fertilization amount was N2 and N3.Therefore,the recommended amount of fertilization is Farmland fertilization measures?N2,225 kg/hm2?...