Research On Character Changes And Drainage Indexes Of Summer Soybean Under Waterlogging Stress

Relying on the crop-water relationship test site of the Wudaogou Hydrological and Water Resources Experiment Station,a summer soybean waterlogging stress experiment was conducted from June to October 2021.The experiment integrated the typical waterlogging stress process in the northern Anhui plain area,analyzed the traits and yield changes of summer soybean under waterlogging stress using Duncan’s ANOVA and multiple linear regression analysis,evaluated the applicability of different types of waterlogging indexes,quantified the degree of influence of different forms of waterlogging stress on summer soybean yield,and constructed a model for the relationship between waterlogging integrated drainage indexes and yield.The study showed that:(1)different forms of waterlogging stress had certain effects on plant height,with the degree of effect being waterlogging followed by submergence>underground waterlogging>surface waterlogging;the main stems of soybean grew adventitious roots to replace lateral roots for respiration under waterlogging stress,and the increment of stem thickness was significantly higher than normal treatment;surface waterlogging and underground waterlogging during the branching stage could promote the maximum photosynthetic chemical efficiency F_v/F_m and photosynthetic performance index of PSII in soybean leaves.The surface waterlogging and waterlogging stress significantly inhibited leaf photosynthetic efficiency at flowering-podding stage and filling and ripening stage.The degree of impact of waterlogging stress on yield indicators was waterlogging followed by submergence>surface waterlogging>underground waterlogging,and the longer the duration of waterlogging stress during branching stage and flowering-podding stage,the more severe the yield reduction of soybean;The response of dry weight index of soybean grain to the form and degree of waterlogging stress was more regular.(2)The waterlogging indexes based on surface waterlogging and underground waterlogging status can better reflect the effect of waterlogging stress on soybean yield,and early surface waterlogging would reduce the yield reduction effect of later underground waterlogging.The yield reduction under waterlogging followed by submergence calculated by surface waterlogging index and underground waterlogging index would lead to larger results.In the branching stage,flowering-podding stage and filling and ripening stage,surface waterlogging in the early stage would reduce the yield reduction of subsequent underground waterlogging to 39.4%,48.3%and 17.9%of the original.Summer soybean has different responses to different forms of waterlogging stress at different growth stages.The corresponding yield reduction rate factors of surface waterlogging index,underground waterlogging index and waterlogging followed by submergence indexes were 0.108,0.172 and 0.211%/(cm·d),respectively.(3)Among different types of yield models improved by equivalent index SEW*,Blank model had the highest prediction accuracy for soybean yield under waterlogging stress at different growth stages,followed by Jensen model,Hiler model and Singh model,The quality of Stewar model is the worst and the average absolute error of soybean yield prediction under waterlogging stress is 0.294,and the deviation is 0.323.The sensitivity of soybean to waterlogging stress obtained by different models is different,which may be related to the influence of the duration of different growth periods on the model indexes.The analysis concluded that the sensitivity of soybean to waterlogging stress in different growth stages according to Hiler model was more reliable as flowering-podding stage>branching stage>filling and ripening stage,so the Blank model and Singh model are applicable to the calculation of sensitivity factors of summer soybean under waterlogging stress.The research results of this thesis revealed the change law of soybean growth characters under different waterlogging processes,put forward the drainage indexes of soybean field under comprehensive waterlogging stress,and improved the soybean yield prediction model under waterlogging stress.The research results can provide a theoretical basis for the formulation of drainage standards for soybean fields.