Effects Of Irrigation Patterns On Greenhouse Gas Emission And Soil Microbial Community Of Winter Wheat Field In North Chian Plain

Nowadays,water resources shortage is one of the most prominent issues of limiting agricultural development in many regions of China.Developing water-saving irrigation and utilizing water with poor quality for agricultural irrigation is an effective way to ease regional agricultural water shortage.Wheat?Triticum aestivum L.?is the main staple crop in China,and securing wheat production is vital to ensure national food security.North China Plain?NCP?is the most important production area of winter wheat in China,and plays a vital role in China's food security.Development of water-saving irrigation techniques and comprehensive utilization of poor quality water for agricultural irrigation will be neccassory in NCP in the future.The effects of irrigation components,such as irrigatton method,irrigation amount and frequency,water quility,and nitrogen application level in fertigation,on greenhouse gas?GHG?emission and soil microbial characteristics in winter wheat field of NCP are studied mainly in this paper,which will be helpful to explore possible effects on local climate change and soil healthy caused by irrigaion pattern changes,to improve water management in winter wheat production,and to develop new irrigation technology for food yield and less greenhouse gas emission in the future.By setting different irrigation pattarns on field and conducting controlled experiments in laboratory,this paper explores differences of GHG emission among three irrigation methods,and effects of different irrigation water and nitrogen levels on soil extracellular enzyme activity and microbial diversity under drip irrigation in winter wheat field,effects of water quality and irrigation frequency on soil GHG emission and soil extracellular enzyme activity,and effects of saline water irrigation on soil extracellular enzyme activity and microbial diversity in lab experiments.The main results are as follows:?1?Changing irrigation methods may impose significant impacts on greenhouse gas emission of winter wheat field in NCP.CO₂ emission was 546.67±12.37 mg m^-2 h^-1 in rainfed field?non-irrigation treatment,NI?,but CO₂ emission were 657.69±12.88 mg m^-2 h^-1 in flooding irrigation?FI?,644.02±9.08 mg m^-2 h^-1 in surface drip irrigation?SDI?and 668.44±11.07 mg m^-2 h^-1 in sprinkler irrigation?SI?,increased significantly by 20.31%,17.81%and 22.27%in FI,SDI and SI,respectively.CH₄ uptake was-57.90±2.39?g m^-2 h^-1 in NI,and were-40.19±2.61?g m^-2 h^-1in FI,-49.42±1.46?g m^-2 h^-1 in SDI,and-37.63±2.30?g m^-2 h^-1 in SI,a decrease of 30.59%,14.65%and 35.01%in FI,SDI and SI,respectively.N₂O emission was 34.43±1.73?g m^-2 h^-1 in NI,and increase by 40.37%?FI?,19.92%?SDI?,and 43.19%?SI?,respectively.The experimental results also indicated that SDI may not only achieved a good yield and IWUE,but also may increased CH₄ uptake for 22.9%and mitigate N₂O emission for 14.6%.Therefore,more attention should be paid to apply SDI in winter wheat field in NCP.?2?Nitrogen application levels had significant influences on soil moisture?SM?,soil pH?pH?,electrical conductivity?EC?,available N?AN?,available K?AK?,Ammonium nitrogen?NH₄⁺?and nitrate nitrogen?NO₃^-?,and irrigation levels had significant influences on SM,pH,EC and NO₃^-under surface drip irrigation and fertigation model.The interaction effects of nitrogen and irrigation was also significant on AN and NO₃^-.Nitrogen and irrigation levels impacted significantly on?-glucosidase,?-glucosidase,cellulases and phosphatase,and the their interaction was also significant?except cellulases?.In addition,experimental results also showed that irrigation water amount was a more important factor of affecting soil microbial community structure,compared with nitrogen application.?3?Water quality and irrigation frequency both had significant effects on CO₂ and N₂O emission and CH₄ uptake.Compared to treatment irrigated with groundwater,CO₂ and N₂O emissions increased by 14.78%and 20.81%,and CH₄ uptake reduced by 17.30%on treatment irrgated with reclaimed and brackish water irrigation reduced significantly CO₂ emission,N₂O emissions and CH₄ uptake by35.16%,40.27%and 30.38%respectively.For irrigation frequency,compared to low frequency irrigation treatment,high frequency irrigation may increased soil CO₂ emission under three irrigation water quality theatment.High frequency irrigation also increased soil CO₂ emission on treatment irrigated with groundwater water and reclaimed,but decreased soil CH₄ uptake on treatment irrigated with brackish water.?4?Saline water irrigation influenced significantly most of soil extracellular enzyme activity.With increasing irrigation water salinity,the activities of?-glucosidase,cellulases,phosphatase,and?-xylosidase decreased significantly,but the activity of N-Acetyl-D-glucosaminidase increased significantly,and the activity of?-glucosidase was not affected significantly.Saline water irrigation may changed soil microbial ability of utilizing carbon source.Low soil salt concentration stimulated microbial activity,which may improved carbon sources utilization by microbes,but when soil salt concentration was more than 6 g L^-1,the restricting effects to microbial ability of utilizing carbon sources were very obvious.