Quantitative Analysis Based On Daily Index Of Wheat Waterlogging Stress

Waterlogging is one of the main agrometeorological disasters that affect the wheat yield in the middle and lower reaches of the Yangtze River.In view of the lack of characteristic quantities that reflect the degree of waterlogging of wheat based on the current low oxygen stress,in order to construct the waterlogging stress day index of wheat at different growth stages,the project has adopted the method of randomized block design of pot experiment for two consecutive years(2021,2022),using waterlogging resistant variety Yangmai 11 and waterlogging resistant variety Zhengmai7698 as the test materials,Two waterlogging modes,single waterlogging and double waterlogging,were set up.The experimental study of wheat waterlogging was carried out in the two growth stages of wheat,namely,jointing,flowering and maturity.Through the determination of soil water content,soil oxygen content,early rainfall index(API)and yield at different growth stages of wheat,as well as the systematic statistical analysis of the measured data,Finally,the criteria for identifying the occurrence of waterlogging damage based on the waterlogging stress daily index of different wheat varieties under waterlogging conditions at different growth stages are obtained,which can provide theoretical and judgment basis for the decision-making of disaster prevention and mitigation when the waterlogging damage occurs in wheat.The main results are as follows:1.The effects of waterlogging duration,waterlogging period and waterlogging tolerance on winter wheat yield were analyzed.The results showed that the duration of waterlogging was significantly negatively correlated with the increase and decrease rate of wheat yield,and the parameters of its linear simulation curve were significantly related to the number of continuous waterlogging,waterlogging date,and waterlogged varieties.2.The characteristic value of waterlogged degree of winter wheat was constructed.The results are as follows:(1)The soil oxygen content gradually decreases with the passage of time and growth period,and its fluctuation is closely related to natural rainfall;The decrease of oxygen content in waterlogged soil during jointing-flowering stage was greater than that during flowering-maturity stage;The soil oxygen content of potted wheat(CK)changes with the growth period in three stages.The first stage is the high value area from sowing to jointing;From jointing stage to grouting stage,it is the second stage of rapid decline;After the grouting stage,it is the low value area of the final stage.According to the summary of single waterlogging test and multiple waterlogging tests,it is determined that before the end of April,the soil oxygen content can be used as the waterlogging index of wheat waterlogging,and the waterlogging threshold of the oxygen content of waterlogged soil is 5 mg/L.(2)The relationship between the days of waterlogging treatment and the relative yield was analyzed.It was found that the yield of "Yangmai 11" and "Zhengmai 7698" and the days of waterlogging treatment showed extremely significant level(P<0.01)and negative correlation.No matter whether the variety was waterlogged tolerant or not,the later the growth period,the greater the impact of waterlogging on the yield of wheat.(3)Based on the analysis of three types of waterlogged indexes of wheat;(1)Oxygen content of soil surface layer: under the single waterlogging treatment in the first year,Yangmai 11 and Zhengmai 7698 suffered slight,moderate and severe waterlogging damage when the soil oxygen was below 5% and lasted for(7d,17 d,25d),(8d,18 d,24d)and(11d,18 d,27d)respectively at the jointing-flowering and flowering-maturity stages;In the second year,under the single waterlogging treatment,the waterlogging lasted(10 d,17 d,25 d),(10 d,15 d,25 d)and(10 d,18 d,26 d),(10 d,17 d,26 d),and suffered from mild,moderate and severe waterlogging damage;Under multiple waterlogging treatments,Yangmai 11 and Zhengmai 7698 were waterlogged continuously(27 d,39 d,49 d),(29 d,39 d,49 d)and(30 d,40 d,49 d 9 and(29 d,39 d,49 d)during jointing,flowering and ripening,respectively.(2)Soil surface water content: under single waterlogging treatment in the first year,Yangmai 11 and Zhengmai 7698 were affected by mild,moderate and severe waterlogging at(10,20,26 d),(10,17,23 d),(14,20,26d)and(10,16,24 d)with daily average relative water content of soil surface layer higher than 95% during the jointing-flowering and flowering-ripening stages;In the second year,under the single waterlogging treatment,they were affected by light,moderate and severe waterlogging respectively after being continuously waterlogged(10 d,17 d,25 d),(10 d,17 d,24 d),(10 d,17 d,25 d)and(8 d,17 d,23 d);Under multiple waterlogging treatments,all of them reached the level of heavy waterlogging.Yangmai 11 and Zhengmai 7698 continued to be heavily waterlogged(29 d,38 d,48 d),(30 d,41 d,48 d),(26 d,39 d,50 d),(29 d,38 d,50 d)at the jointing-flowering and flowering-maturity stages,respectively.(3)API index: under the single waterlogging treatment in the first year,Yangmai 11 and Zhengmai 7698 were affected by light,moderate and severe waterlogging at the time when the API value of jointing-flowering and flowering-maturity stage was more than 95 mm(2 d,8 d,16 d),(2 d,6d,12 d)and(4 d,11 d,17 d),(2 d,7 d,12 d);In the second year,under a single waterlogging,it was affected by mild,moderate and severe waterlogging for(8 d,13 d,17 d),(4 d,11 d,17 d),(2 d,6 d,10 d)and(2 d,5 d,10 d)respectively;Under multiple waterlogging treatments and multiple waterlogging treatments,Yangmai 11 and Zhengmai 7698 were affected by light,moderate and severe waterlogging damage during jointing,flowering and flowering,respectively(4 d,12 d,21 d),(3 d,11 d,19 d)and(4 d,12 d,19 d),(2 d,7 d,13 d).3.The threshold value of winter wheat waterlogging was established.The results are as follows:(1)WI index can accurately express the waterlogging mechanism model,that is,the relationship between WI index and wheat yield can be divided into two parts.When WI index is less than or equal to 5.3("Yangmai 11")and less than or equal to 6.0("Zhengmai 7698"),WI index is positively correlated with yield.The larger WI index is,the higher its yield is.On the contrary,when WI index is greater than 5.3("Yangmai11")and more than 6.0("Zhengmai 7698"),WI index is negatively correlated with yield,The higher the WI index,the lower the yield.(2)Wheat waterlogging day index(DWI)can well represent the time and intensity of wheat waterlogging.The cumulative WI value and the SPAD value of wheat leaves have an obvious negative linear correlation.The heavier the early waterlogging,the lower the chlorophyll content of wheat.