Effects Of Subsoiling And Irrigation Systems On Carbon Emission And Water Use Efficiency Of Winter Wheat

Shandong Province is one of the most important agricultural regions in China and the main planting area of winter wheat.Winter wheat production,as a basic guarantee industry supporting the development of the country,occupies an important position in Shandong Province and even the North China Plain.Reducing greenhouse gas emissions and saving water are necessary ways to achieve sustainable agricultural development.However,long-term rotary tillage and global climate change have had a negative impact on the soil plow layer,resulting in a decrease in the availability of soil water,and the problem of agricultural water use has become increasingly prominent.Subsoiling is an effective measure to improve the structure of the soil arable layer.In addition,proper irrigation management is a necessary measure to ensure the stable production of winter wheat and improve water use efficiency.However,the coupling effect of the combination of subsoiling and irrigation on winter wheat water use efficiency and carbon dioxide emissions is still unclear.This study was conducted in the 2019–2021 winter wheat season at the Agronomy Experimental Station of Shandong Agricultural University,in order to find out the response mechanism of winter wheat carbon and water use efficiency under the conditions of subsoiling and different irrigation systems.The experimental design method is split zone test.The main zone has two farming methods: subsoiling 35 cm(S)and rotary tillage 15 cm(R);the secondary zone has three irrigation treatments: no irrigation during the growth period(I0),irrigation 60 mm at jointing stage(I1)and irrigation 60 mm at the jointing and heading stages(I2)respectively.There are 6 treatments in the experiment,3 replicates for each treatment,a total of 18 plots.The experiment measures the key water consumption and carbon emission related factors of winter wheat: yield,water use efficiency,carbon emission efficiency,and soil carbon sequestration rate.This study provides solid theoretical support and practical guidance for farmland conservation and sustainable development of agricultural production in winter wheat producing areas of North China Plain The results showed that:1.Soil moisture and evapotranspirationUnder the same irrigation treatment,35 cm subsoil cultivation can effectively increase the soil volumetric water content and soil water storage capacity of the 0–130 cm soil layer during the growth period of winter wheat compared with 15 cm rotary tillage.The subsoiling treatment has better soil water retention and lifting effects than rotary tillage treatment.On the contrary,under the same irrigation treatment,the evapotranspiration of the subsoiling treatment is lower than that of the rotary tillage treatment,and the subsoiling reduces the ineffective evaporation of soil water and reduces the water consumption of the farmland.Soil water content,soil water storage and evapotranspiration increased with the increase of total irrigation water.2.Soil respiration and carbon emissionsThe soil moisture retention effect of subsoiling treatment is better than that of rotary tillage treatment.In addition,subsoiling increases soil porosity,accelerates the migration and diffusion of gas in the soil,and subsoiling provides a better environment for the growth and development of winter wheat roots.Under these moisture and soil conditions,subsoiling treatment significantly increased the soil respiration rate,resulting in an increase in total carbon emissions.Compared with non-irrigation treatment,irrigation treatment significantly increased soil respiration rate and total soil carbon emissions.3.Photosynthesis and dry matter accumulationWith the increase of irrigation,the photosynthetic performance and dry matter accumulation of winter wheat increased significantly.Under better water conditions,compared with rotary tillage,subsoiling treatment increased the chlorophyll content of flag leaves,and at the same time delayed the decline of chlorophyll content of flag leaves in the late growth period,and maintained a relatively high net photosynthetic rate in the late growth period.The high above-ground dry matter accumulation provides a physiological basis for the accumulation of light-contracted organic matter and yield formation in winter wheat.4.Yield and water use efficiencyThe optimal treatment for grain yield from 2019 to 2021 is subsoiling combined with 60 mm irrigation at the jointing and heading stages,but the carbon emission of this treatment is higher than that of the treatment with only irrigation at jointing stage with 60 mm irrigation of subsoiling.The carbon emission efficiency and carbon sequestration of the above two treatments are both at a relatively high level,and there is no significant difference between the two.However,the water use efficiency of the treatment only at jointing stage with 60 mm irrigation under subsoiling was significantly higher than that of other treatments.The results show that the combination of 35 cm subsoiling and 60 mm irrigation at the jointing stage is an efficient production model for improving the carbon emission efficiency and water use efficiency of winter wheat in the North China Plain.