Laboratory Study On N₂O Emission Characteristics In Different Paddy Soils Under Cycle Of Flooding And Drainage Conditions

The total area of paddy field planting in China is about 23 million hm².At the same time,there are many different developmental parent materials in paddy soil,such as:brick red soil,river alluvial,Quaternary red soil,fluvo-aquic soil,etc,and water regulation and fertilization management begin to become rice.The main measures of production:on the one hand,water regulation and fertilization can regulate the soil micro-environment,which in turn affects the absorption and utilization of water and nutrients by crops;on the other hand,the high input and low utilization of nitrogen fertilizer not only causes the loss of nitrogen fertilizer,but also increases N₂O and CH₄.The emission of greenhouse gases such as CO₂ also increases the nitrogen pollution of water bodies to some extent.Therefore,exploring the effects of water and nitrogen fertilization on the nitrogen cycle of soil system is beneficial to improve the efficiency of water and fertilizer utilization and provide a theoretical basis for regulating greenhouse gas emissions from soil systems.Therefore,we selected 5 kinds of paddy soils such as Yingli brick red soil in Leizhou Peninsula,alluvial deposits in two regions,and Quaternary red soil in two regions.Urea was added as nitrogen fertilizer and used under flooding and drying conditions.Conventional experimental method,static box method and correlation analysis method were carried out to study the characteristics of nitrogen migration and transformation,greenhouse gas N₂O emission and its influencing factors in different paddy soils.The main conclusions are as follows:?1?The migration ability of exogenous nitrogen?NH₄⁺-N?in different paddy soils is as follows:brick red soil>Quaternary red soil>river alluvial deposit;the transformation ability of different paddy soils to external nitrogen is:brick red soil>Quaternary red soil,river alluvial deposits.Therefore,the red soil NH₄⁺-N is mainly distributed in 0²0 cm soil layer,the river alluvial deposits are mainly distributed in 0⁵ cm soil layer,and the Quaternary red soil is mainly distributed in 0¹0 cm soil layer;but brick red soil and river alluvial deposits The Quaternary red soils NO₃^--N and NO₂^--N are mainly distributed in the 0⁵ cm soil layer;?2?The peak N₂O emission of different paddy soils under flooding and drying conditions is as follows:During the flooding period,only the red bricks showed peak discharges on the 21st day of flooding.In the dry period,brick red soil,river alluvial deposits,Quaternary red soil Emission peaks on the second day after falling;?3?The N₂O emission capacity of different paddy soils under flooding and drying conditions is as follows:N₂O emission capacity in the flooding period is brick red soil>Quaternary red soil>river alluvial deposit;N₂O emission capacity performance in the middle and late dry season For Quaternary Red Soil>Brick Red Soil>River Alluvial;?4?The rate of consumption of exogenous nitrogen sources is roughly as follows:brick red soil>Quaternary red soil>river alluvial;?5?Under the condition of adding urea nitrogen fertilizer,soil moisture,NH₄⁺-N,NO₃^--N and other soil factors have significant stimulating effects on N₂O emissions from paddy soil under dry-wet changes.