| As a new type of soil conditioner,biochar is applied to soil to improve soil structure and nutrition and affect soil N2O emissions.However,effects of biochar on soil N2O emissions and soil structure are mostly concentrated on short-term tests,which limits the understanding of effects of biochar on N2O emissions and soil structure improvement.This experiment relies on a long-term field location experiment,and four biochar levels(0,5000,10000,20000 kg·hm-2,B0,B5,B10,B20,respectively and the same amount of biochar was applied to the soil in 2011 and 2016 wheat season before tillage,respectively.)were set up through measuring soil N2O emission and soil properties such as soil temperature,water,ammonium nitrogen,nitrate nitrogen and soil water-stable aggregates in the wheat season from 2016 to 2018 to study the effects of of biochar on N2O emission and soil water-stable aggregates,which providing a theoretical basis for the promotion of biochar in the Loess Plateau.The main conclusions are as follows:?1?Effect of biochar application on N2O emissionSoil N2O emissions are mainly concentrated after fertilization application.The contribution rate to N2O cumulative emission was relatively large during this period,which reached 78.23%?48.20%in 2016-2017 and 2017-2018 wheat season respectively.Due to the differences in rainfall and temperature,the cumulative N2O emissions in each treatment in 2017-2018 wheat season decreased by 69.63%-83.48%as a whole compared with that in 2016-2017 wheat season.Effects of biochar on N2O emission varied with application amount and year.Biochar decreased N2O emission at low dose(5000kg·hm-2)and increased N2O emission at high dose(20000kg·hm-2)in 2016-2017 wheat season.B20treatment significantly increased N2O emission intensity,while other biochar treatments had no significant difference with B0 treatment.Biochar treatment increased N2O emission in 2017-2018 wheat season compared with B0 treatment.However,B20 treatment showed outstanding performance in increasing wheat yield,and there was no significant difference in N2O emission intensity in B20 compared with B0 treatment in 2017-2018 wheat season.?2?Analysis of the environmental factor of affecting soil N2O emission in biochar applicationBiochar application can increase soil temperature,but had no significant difference compared with the control.And the application of high amount of biochar significantly increased soil water content,nitrate nitrogen,ammonium nitrogen and the contents of>2mm,1-2mm soil water-stable aggregate compared with the control.The correlation analysis between soil N2O emission and soil physical and chemical properties showed that N2O emission was positively correlated with soil water content and ammonium nitrogen content in 2016-2017 wheat season,while in 2017-2018 wheat season,there was a significant positive correlation between N2O emission and soil ammonium nitrogen and nitrate nitrogen content.In addition,there was a significant positive correlation between N2O emission and the contents of 1-2mm water-stable aggregates in two seasons.The results of the two years indicated that the biochar may affect N2O emission mainly by changing the nitrogen content of the soil and the contents of soil 1-2 mm water-stable aggregate.?3?Effects of biochar application on soil water aggregate and wheat yieldThe application of high amount of biochar increased the values of contents of>0.25mm macro-aggregates(R0.25)?mean weight diameter?MWD?,geometric mean diameter?GMD?of soil water-stable aggregates,and improved the stability of water-stable aggregates.In addition,the application of biochar increased the content of organic carbon and total nitrogen in>0.25mm soil water-stable aggregates,which were mainly concentrated in>2mm macro-aggregates.The stability of soil water-stable aggregates in2017-2018 wheat season was lower than that in 2016-2017 wheat season,and the content of soil organic carbon and total nitrogen in>2mm soil water-stable aggregates is higher than that of in 2016-2017 wheat season.In addition,the application of biochar increased the yield of winter wheat,and the yield of winter wheat was the highest in B20 treatment. |
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