Effects Of Biochar On Soil Greenhouse Gas Emission And Crop Nitrogen Utilization

Nitrogen loss control has been an important direction for nitrogen fertilizer management in farmland.The relatively stable physical and chemical properties of biochar and its special surface structure make people see its potential to influence nitrogen activity.Therefore,exploring the role and mechanism of biochar on soil nitrogen behavior is of positive significance for the development of nitrogen fertilizer control technology.The leaching soil column was used in combination with gas chromatography and phosphatidylcholine fatty acid?PLFAs?analysis techniques to observe the dynamics to GHGs emissions and the effects on nitrogen utilization of crops,changes of microbial community structurein in red and Fluvo-aquic soil,discuss the key factors in the regulation of soil nitrogen activity by biochar,and the effect of biochar of soil nitrogen loss control.The main findings are as follows:The biochar application has a greater impact on greenhouse gas fluxes in Fluvo-aquic soil than red soil,and the two soils show different emission trends.The accumulated N₂O emission in Fluvo-aquic soil was significantly higher than that in red soil.With the increase of biochar,the accumulated N₂O emission from Fluvo-aquic soil was significantly reduced by 6.5%-26.6%compared with single application of N fertilizer.The cumulative N₂O emissions from red soil increased with the increase of biochar addition.Compared with the single nitrogen fertilizer treatment,the accumulated N₂O emissions from red soil increased by 14.7%-54.3%.Biochar application significantly increased CO₂emissions from Fluvo-aquic soil,with a significant increase of 25.9%in cumulative emissions,but no significant effect on CO₂ cumulative emissions from red soil.In addition,CH₄ emissions in both soils showed no regular changes under different treatments,and cumulative CH₄ emissions were generally around 0.At the same time,with the application of biochar,the greenhouse gas emission intensity in Fluvo-aquic soil increased significantly by 68.0%-76.8%,while the addition of biochar has no significant effect on the greenhouse gas emission intensity of red soil.The application of biochar in red soil and Fluvo-aquic soil has different effects on the growth of Pakchoi.Compared with the treatment without biochar,the application of biochar significantly reduced the aboveground and underground biomass of Pakchoi in the Fluvo-aquic soil,with a drop of65.0%-79.4%.Biochar application significantly increase the aboveground and underground biomass of Pakchoi in red soil,with an increase of 30.6%-65.8%.With the increase of biochar application,the root length of Pakchoi in Fluvo-aquid soil decreased by 11.5%-30.1%,and the root surface area decreased by45.6%-55.9%.The ratio of root to shoot was increased first and then decreased,but the root length of Pakchoi in red soil had no significant effect,but the root surface area increased by 12.3%-32.2%.Applying biochar in Fluvo-aquic soil can reduce the nitrogen absorption efficiency of Pakchoi by64.7%-73.5%,the apparent utilization rate of nitrogen by 83.3%-94.4%,and the nitrogen partial productivity by 65.1%-79.4%.The application of biochar in red soil increased the nitrogen absorption efficiency of Pakchoi by 44.7%-59.6%,increased the apparent utilization rate by 73.9%-83.8%,and increased the nitrogen partial productivity by 30.1%-63.1%.The application of biochar significantly reduced the nitrate content of Pakchoi in red soil and Fluvo-aquic soil,and the decline ranged from40.9%-84.6%and 18.8%-75.0%,respectively.Biochar application reduced the soil bulk density of two soils and significantly increased the soil organic carbon content by 57.1%-78.7%in the Fluvo-aquic soil,and the red soil increased by11.2%-59.9%.Compared with single application of nitrogen fertilizer,biochar application significantly increased NO₃^--N content in Fluvo-aquic soil.When the amount of biochar added was 1%and 2%,the content of soil nitrate was 24.4%higher than that of MN treatment 28.6%.The nitrate content in red soil increased significantly with the increase of biochar addition,and the addition of 2%and 4%biochar treatment increased the growth of 54.6%and 39.2%.The application of biochar has no significant effect on the pH value of fluvo-aquic soil,and significantly increases the pH of red soil.The application of biochar in fluvo-aquic soil increased the content of soil bacteria PLFAs with the increase of biochar application amount,and the increase ranged from 8.7%to 36.2%.Compared with single application of nitrogen fertilizer,the content of gram-negative bacteria in biochar application soil decreased.27.6%-38.4%,of which the addition of 0.5%and 1%of biochar significantly reduced the bacterial content by 33.7%and 27.3%.Biochar application had no significant effect on the fluvo-aquic soil fungi,actinomycetes,Gram-positive bacteria,and fungal/bacterial ratios;application of biochar had no significant effect on the total PLFAs of red soil.Correlation analysis showed that biochar can affect soil microbial activity by regulating soil pH.Biochar application in red soil has no significant increase in the greenhouse gas emission intensity,with a significant increase in soil carbon sequestration,promotes the growth and development of Pakchoi roots,increases its yield,reduces the nitrogen residue in red soil,and improves the utilization efficiency of nitrogen fertilizer.It has a good ecology benefits.Biochar application to Fluvo-aquic soil can increase the intensity of greenhouse gas emissions,inhibit the development of Pakchoi roots,reduce its yield,and reduce the use efficiency of nitrogen fertilizer.The effective and safe application of biochar to Fluvo-aquic soil still needs further exploration.