Effects Of Soybean And Corn Growth And Soil Nitrogen Application On Soil N₂O Emission

In order to understand the effects of crop growth and soil nitrogen application on N2O emissions from soil,it is theoretically enriched about the effect of different crop types and soil N application on N2O emissions from farmland,and provide a scientific basis for N2O emission reduction in farmland ecosystems.In this study,two kinds of nitrogen application levels(250mg kg-1and 80mg kg-1)were used to carry out pot experiments on soybean and maize.The emission rate of N2O was measured by static box sampling and gas chromatography during the experiment.The main results of this study were as follows:1.The seasonal variation of soil NaO emissions under the growth of crops was significantly different from the bare soil under the same conditions,and the seasonal variations of N2O emissions from diverse crop types were distinct.The seasonal variation of N2O in the bare soil was low-high-low.And the relationship between the emission rate and the time of sowing was significant,respectively the correlation coefficients for the two nitrogen levels are 0.4475 and 0.5158.The seasonal variation of N2O emission in soybean soil was high-low-high,and the relationship between the emission rate and the time of sowing was very significant.Respectively the correlation coefficients for the two nitrogen levels are 0.5680 and 0.6065.And the seasonal variation of N2O emission in corn soil was high-low-low.The relationship between the emission rate and the sowing time was highly significant exponentially.The correlation coefficient was 0.6817 and 0.7021 for the two nitrogen levels,respectively.2.Crop growth reduced soil N2O emissions and emissions,but the N2O emission rate and emissions of different crop types were different.The highest emission rate of bare soil is 124.30?341.68ug N m-2h-1,and the cumulative emission is 94.93?299.01mg Nm-2 at the same time.The highest emission rate of soybean was decreased by 38.93%?47.11%and the total N2O emission of the whole period decreased by 30.50%?55.46%.The highest N2O emission and cumulative emissions of corn were reduced by 42.95%?53.15%and 56.84%?74.67%respectively.3.The N2O emissions of bare soil and crop soil in different periods are different,and the emissions of soybean and maize are different at each stage.The emissions per stage of the bare soil were in the middle period ? the earlier stage ? the late stage;the emissions per stage of the soybean soil were influenced by the amount of nitrogen,the low nitrogen level was in the late period ? the early stage ? the middle period,and the high nitrogen level was in the earlier period ? the late stage and the middle period;the high and low levels of each stage of the corn soil were in the early stage ? middle period ? later.4.Nitrogen application can increase soil N2O emission and increase N2O emissions.Under high nitrogen level,the N2O emission rate of bare soil,soybean soil and corn soil increased by 214.90%,101.88%and 84.93%,respectively,compared with that under low nitrogen level.Under high nitrogen level,the cumulative N2O emissions from bare soil,soybean soil and corn soil were 3.15 times,2.02 times and 1.87 times of low nitrogen level respectively.5.Crop growth has changed the relationship between soil N2O emission rate and temperature,and fertilization will change the sensitivity of soil N2O emission to temperature.There is a very significant positive correlation between the N2O emission rate and the temperature of the high nitrogen bare soil,but the correlation coefficient at the high nitrogen level is higher than the low nitrogen level,and there is no correlation between the soil surface temperature and the soil temperature.The atmospheric temperature is affected by the nitrogen application.There was an exponentially negative correlation between low nitrogen soybean soil and atmospheric temperature,and the correlation coefficient was-0.4066,while the high nitrogen soybean atmospheric temperature was significantly negatively correlated with a correlation coefficient of-0.3784.And there is no significant correlation between corn soil and temperature.6.The growth of different crops and the distribution of nutrient contents in different parts were affected by nitrogen application.The effect of Nitrogen Application on the growth and yield of soybean was less.Nitrogen application changed the distribution of nitrogen and phosphorus in different parts of soybean,did not change the distribution trend of potassium content in different parts of soybean,and the effect of nitrogen fertilizer on the growth and yield of maize was great.Nitrogen application changed the distribution of N,P and K content in different parts of maize.7.The basic physical and chemical properties of soil will be changed by crop growth and nitrogen application.Under the same conditions,the content of soil pH,organic matter,NO3--N available nitrogen,available phosphorus and available potassium in soil increased,and the variation of NH4--N was different because of different plant types and nitrogen application.In the soil without crop,nitrogen application can reduce soil pH,and increase soil organic matter content,NO3--N,NH4-N,available nitrogen,available phosphorus and available potassium.