Effects Of Different Tillage Patterns On Greenhouse Gas Emission And Nitrogen Uptake Of Rice

In recent years,no-tillage has been widely applied in paddy fields because of its advantages such as cost-saving,efficiency increasing,fertilizer cultivation and emission reduction.However,long-term no-tillage also has some problems,such as high nitrogen loss,low nitrogen uptake of rice and unstable yield.Ridge with no-tillage has been widely used in south China as one of the methods to solve the problems of no-tillage,which could enhance the light and temperature resources of paddy fields and improve soil microenvironment.However,at present,most studies tend to focus on the change of soil fertility,crop physiological characteristics and yield by box-no-tillage technology,and the influence of box-no-tillage technology on the change of nitrogen in the paddy soil is not clear,and the internal relationship between the nitrification of paddy soil and nitrogen uptake by rice is ignored.At the same time,although most studies have paid attention to the greenhouse gas emission reduction of paddy fields by the cage no-tillage technology,there is a lack of comprehensive ecological and economic evaluation of this technology in rice cultivation.Compartments for no-till so the changes in the technology of paddy soil nitrogen,explore the compartments for paddy soil nitrification under no-till techniques and key microbes are intrinsically related to n uptake of rice,through different evaluation methods of compartments for no-tillage paddy fields to evaluate ecological economic benefit,but for the promotion of the technology and provide theoretical basis for related research.Therefore,this research and the 2017-2019 in Hubei province founded Dafa temple town to carry out field trials,the design of different tillage patterns on paddy soil microorganisms and functional microbial community abundance,rice nitrogen absorption,the effect of greenhouse gas emissions,and through the carbon footprint,energy balance and economic benefit of different tillage modes of paddy field to evaluate ecological economy.The specific experimental treatments included:conventional intensive tillage（CT）,conventional flat no-tillage（FNT）and ridge with no-tillage（RNT）.In this study,the changes of soil nitrification and denitrification and soil nitrogen were discussed from the perspective of soil nitrogen key microorganisms.Combined with the root stimulation of rice nitrogen uptake,the internal relationship between rice nitrogen uptake and nitrification and denitrification functional microorganisms was discussed.At the same time,from the perspective of greenhouse gas emissions,this study evaluates different tillage models through carbon footprint,energy budget and net ecological economic benefits,and expounds the ecological and economic benefits of different tillage models.After three years of experiment,the research results are as follows:1)Tillage significantly affected soil redox potential（Eh）,nitrate（NO₃^-）and ammonium（NH₄⁺）contents.Compared with CT treatment,NO₃^-content in RNT and FNT treatment increased by 3.8%-16.6%and 5.8%-19.2%,respectively,with no significant difference between RNT and FNT.Compared with CT and FNT treatments,NH₄⁺content in RNT treatment was significantly increased by 5.6%-32.6%and 3.2%-19.4%,respectively.Soil in rice growth period was in a reduction state,and soil Eh showed a trend of RNT>FNT>CT under different tillage patterns.2)Soil microbial biomass carbon（MBC）,soluble organic carbon（DOC）and organic carbon（SOC）contents were significantly affected by tillage patterns.No-tillage significantly increased soil DOC content.Compared with CT treatment,soil SOC content in RNT and FNT treatments increased by 7.2%-11.6%and 10.3%-15.0%,respectively,but there was no significant difference between RNT and FNT treatments.Compared with CT treatment,the MBC content of RNT treatment increased by 15.5%-34.9%and 4.48%-23.0%,respectively.Compared with FNT treatment,RNT treatment significantly increased MBC content by 9.8%-15.4%.3)Soil nitrification,soil microbial community and abundance of key functional microorganisms were significantly affected by tillage patterns,but soil denitrification was not affected.Compared with FNT and CT treatments,the mean nitrification rate of soil under RNT treatment was significantly increased by 19.4%-39.5%and 6.2%-16.3%,respectively.Compared with CT and FNT treatments,RNT treatment significantly increased the total PLFAs,bacterial,fungal and actinobacteria communities,increased the bacterial diversity index,and improved the soil nutrition（G+/G-）and soil aeration（MUFA/STFA）.The copy number of AOA gene in RNT treatment increased by 35.1%-71.7%and 26.3%-46.7%,respectively,compared with FNT and CT treatment.Compared with CT treatment,the copy number of AOB gene in RNT and FNT treatment increased by17.4%-60.2%and 9.3%-26.3%,respectively.In terms of denitrification genes,the copy number of nir S gene in FNT treatment was 1.35-1.96 times and 1.28-1.50 times of CT and RNT treatment,respectively,and the copy number of nir K gene was 1.46-1.91 times and1.30-1.39 times of CT and RNT treatment,respectively.4)Compared with CT and FNT treatment,RNT treatment significantly increased root length,root surface area and root volume,and increased root nitrate reductase activity.Compared with CT,RNT and FNT treatments increased rice yield by 15.5%-33.3%and7.0%-22.1%,respectively.Compared with CT,RNT treatment significantly increased the dry matter weight of rice panicle by 9.1%-16.6%.Compared with CT and FNT treatments,the panicle nitrogen uptake of rice under RNT treatment was significantly increased by8.8%-21.4%and 8.2%-19.2%,respectively,and the total nitrogen accumulation of RNT was significantly increased by 10.0%-20.4%and 4.0%-18.5%,respectively.5)Tillage patterns significantly affected soil CH₄ emissions,total greenhouse gas emissions and CF,but had no effect on N₂O emissions.Compared with CT and FNT treatments,RNT treatment reduced soil CH₄ emissions by 29.5%and 9.9%,respectively.Compared with CT treatment,FNT and RNT treatment reduced the total greenhouse gas emissions by 15.8%and 23.1%,respectively.Compared with CT and FNT treatment,RNT treatment reduced CF by 34.3%and 15.3%.Compared with CT treatment,RNT treatment significantly increased net energy by 41.2%,energy efficiency by 25.0%and energy productivity by 26.7%,and reduced specific energy by 24.7%.NEEB was highest in RNT treatment,which was 1.66 and 1.20 times higher than CT and FNT treatment.In conclusion,three years of field experiments showed that box no-tillage improved soil physical and chemical properties,increased soil nitrification rate,stimulated rice root growth,and thus increased rice nitrogen uptake.Crate no-tillage can reduce greenhouse gas emissions,reduce carbon footprint,improve energy efficiency,increase rice yield and economic benefits,and is a new low-carbon and green paddy field tillage model.