Study Of Different Straw Returning Amount On Soil N₂O Emission In The Wheat-maize Rotation System

The field experiment was carried out during 2014-2016at the experimental station of Tumen Village,in Dawenkou Town,Daiyue District,Tai'an Shandong,P.R.China.Split plot field experiment was conducted in summer corn in 2012 and 2013.The main factor was wheat and maize planting region?T?and bare region?E?,the deputy factor was different amount of straw returning,including without straw returning?0?,returning 1875 kg.ha-1 wheat straw and 2000 kg.ha-1 maize straw?1?,returning 3750 kg.ha-1 wheat straw and 4000 kg/ha maize straw?2?,returning 5625 kg.ha-1 wheat straw and 6000 kg.ha-1 maize straw?3?,and returning 7500 kg.ha-1 wheat straw and 8000 kg.ha-1 maize straw?4?.The two-year field test results showed that straw returning affects N₂O flux by affecting physical and chemical properties such as soil water content,temperature,and organic carbon content.The main results were as follows: 1 Influence of different straw returning amounts on N₂O fluxThe N₂O flux was affected by straw returning amounts significantly.It was increased significantly with the increase of straw returning amounts,however,the increased rate reduced gradually.Compared with those without straw returning farmland,N₂O flux increased by 19.16%,32.65%,43.79% and 52.88% when returning by 3875,7750,11625 and 15500 kg.ha-1.N₂O flux in maize season was significantly higher than that in wheat season,and the average flux and total amount were 2.99 times and 1.27 times of wheat season.2 The influence of climatic conditions on coil N₂O fluxThe influence of climatic conditions on N₂O flux changed significantly with the change of rainfall and temperature.N₂O flux was increased when the temperature raised and rain fall amount increased..3 The influence of crop growth on N₂O fluxThe influence factor of crop on N₂O flux was negative indicated that crop growth could inhibit N₂O flux.The variation range of each treatment impact factor was-0.13 ^-0.23 during 2014-2015 while it was-0.21 ^-0.27 during 2015^-2016.Crop growth promoted N₂O flux after wheat season and maize season irrigation and fertilization.Further analysis showed that the change of NO₃^--N content in 0-60 cm soil layer was the main factor affecting N₂O flux.4 Analysis of N₂O flux main factor affecting under different straw returning amountThe climate factor and straw returning amount promoted N₂O flux,while crop growth showed an inhibitory effect on N₂O flux.The enhancement of climate factor was higher than straw returning amount when the amount was less than 7750 kg.ha-1,however,the latter was greater than the former when the amount was more than 11625 kg.ha-1.5 Characteristics of soil chemical properties under different straw returning amountThe effect of straw returning on soil temperature?0-10 cm?showed that soil temperature could be increased in the early stage especially in pre-winter stage of crop growth while decreased in the later stage.Compared with those without straw returning farmland,soil temperature increased with 3.48%,5.89%,7.86% and 9.25% when straw returning by 3875,7750,11625 and 15500 kg.ha-1.Straw returning changed the soil physical and chemical properties of the 0-60 cm soil layer and had a surface enrichment phenomenon.It could increase soil water content significantly?0-60 cm?,but the soil water content of the soil layer?60-180 cm?remained its original state.Soil water content increased with 4.76%,3.83%,6.63% at 0^-20 cm,20-40 cm,40-60 cm soil layer.The soil organic carbon content increased with 1.49%,7.48%,2.88% and 5.41% respectively when the straw returning amounts increased by 3875 kg.ha-1.The soil total nitrogen content increased with 2.54%,6.32% and 5.35%,respectively.The soil NH₄⁺-N content increased with 6.38%,3.77%,2.21% and 1.23%,respectively.The soil NO₃^--N content increased with 4.35%,2.13%,1.86% and 0.57% respectively.6 The influence of soil physical and chemical properties on N₂O fluxThe correlation analysis showed that the N₂O flux had an exponential correlation with soil temperature?0-10 cm?.On the planted land soil,N₂O flux had an exponential correlation with the soil water content at 20-60 cm soil layer.On the bare land soil,N₂O flux had an exponential correlation with soil NH₄⁺-N content and NO₃^--N content at 0-60 cm soil layer.