Effects Of Irrigation System And Straw Returning Method On Water Use Efficiency And Carbon Emission Efficiency Of Winter Wheat

North China Plain is an important winter wheat producing area in China.Water shortage is the main factor restricting the safe and stable production of winter wheat in the North China Plain.With the development of society,the carbon emission problem has been paid more and more attention.The combination of appropriate irrigation system and straw returning has positive effects on stabilizing winter wheat yield,improving water use efficiency and reducing farmland carbon emission.This experiment was conducted at the Agricultural Experimental Station on Panhe Campus of Shandong Agricultural University during the winter wheat season from 2020 to 2022.In order to explore the effects of different irrigation systems combined with different straw returning methods on the water use efficiency and carbon emission efficiency of winter wheat,three irrigation treatments were set:Winter wheat was irrigated no（I0）,only 60 mm（I1）at jointing stage,and 60 mm（I2）at jointing stage and heading stage.At the same time,two kinds of returning modes were set,namely straw burying returning（SR）and straw mulching（SM）.The experiment consisted of six treatments,each of which was repeated three times.A total of18 cells were set up in this experiment.It mainly measured and calculated winter wheat yield,SWC（soil water content）,ET（evapotranspiration）,soil respiration rate,WUE（water use efficiency）and CEE（carbon emission efficiency）.1.Irrigation at jointing stage significantly increased the number of single stems of winter wheat,and irrigation at jointing stage and heading stage increased the leaf area index（LAI）,net photosynthetic rate of flag leaf,transpiration rate and above ground dry matter accumulation of winter wheat.During 2020–2021,the yield of I1 and I2 treatment was significantly increased by 20.45%and 24.61%compared with that of I0 treatment,and during 2021–2022,it was significantly increased by 19.38%and 28.56%.Compared with SM treatment,SR treatment increased single stem number,LAI,net photosynthetic rate of flag leaf,transpiration rate and above ground dry matter accumulation of winter wheat,and finally increased winter wheat yield.The yield of SR treatment was increased by 5.15%and 7.47%,respectively,compared with SM treatment.SR-I2 had the highest yield of all treatments.2.The experimental results showed that irrigation significantly increased soil volume water content and evapotranspiration.During the filling period of winter wheat,the average soil volume water content in 0–160 cm soil layer in I1 and I2 treatments was significantly increased by 3.08%and 12.03%in 2020–2021 compared with that in I0 treatment,and by 5.06%and11.94%in 2021–2022,respectively.Compared with SR treatment,SM treatment increased the SWC of 0–40 cm soil layer.In the 2020–2021 winter wheat season,the volume moisture content of 0–10,10–20,20–30 and 30–40 cm soil in SM treatment was increased by 3.68%–6.62%compared with SR treatment,respectively,and by 2.95%–5.71%during 2021–2022.Compared with I0 treatment,the ET of I1 and I2 treatment was significantly increased by 15.32%and28.03%during 2020–2021,respectively,and was significantly increased by 14.68%and 27.99%during 2021–2022.There was no significant difference in ET between the two straw returning treatments.3.Irrigation and straw mulching increased soil respiration rate and CO₂-C cumulative emission.During 2020–2021,soil CO₂-C cumulative emission in I1 and I2 treatments were significantly increased by 8.81%and 18.56%compared with that in I0 treatment,and significantly increased by 2.96%and 14.50%during 2021–2022.The CO₂-C cumulative emission in SM treatment were 5.16%and 10.31%higher than those in SR treatment,respectively.In the two winter wheat seasons,comprehensive WUE and CEE,the 60 mm irrigation at jointing stage combined with straw burying returning showed the best performance,which could better balance the contradiction between stable yield,water saving and emission reduction,and had a positive impact on the efficient agricultural water use and the reduction of farmland carbon emission.Therefore,the combination of irrigation of 60 mm in jointing period and straw burying returning treatment is conducive to the stable yield,water-saving and low-carbon production of winter wheat,which is an efficient production mode suitable for promotion in the North China Plain.