Occurrence Trend Of Drought And Heat Damage Of Summer Maize In Hebei Plain And Its Control Technology Effect

Influenced by monsoon climate,summer maize in Hebei Plain has frequent abnormal weather,such as short abnormal high temperature,continuous rain,few sunshine,strong wind and drought.Among them,the emergence stage,big mouth stage and drought in the early filling stage are drought.High temperature in the stage of male spraying and powder dispersing has an important impact on maize yield formation.Firstly,the annual temperature and precipitation changes of 32 counties(cities and districts)in Hebei Plain from 1971 to 2018 were analyzed by using the climate change tendency rate method.Secondly,86 counties(cities and districts)in Hebei Plain from 1971 to 2018 were selected to analyze the variation characteristics of summer maize season mean temperature and precipitation by using the method of climate change tendency rate.(Mi)The characteristics of drought occurrence in sowing-emergence stage(June 1-20),mouthful stage(July 21-30)and early filling stage(September 1-10)were analyzed,and the characteristics of high temperature occurrence during pollination period(August 1-25)during high temperature cumulative days(EDD)and high temperature occurrence days(EHD)were used.Based on this,field experiments were conducted in combination with the actual situation of summer maize production in Hebei Plain.Two drought prevention and control technologies,i.e.subsoiling and fertilization integrated sowing method and polyacrylamide high-efficiency water-retaining agent,plant regulator spraying and high-temperature resistant variety screening,were set up to study the effects of different prevention and control technologies on drought and heat disaster prevention and reduction of summer maize.(1)From 1971 to 2018,the annual precipitation in Hebei Plain showed a decreasing trend.In the southern part of Hebei Plain(Xingtai and Handan)-10.04 mm/10 years,in the central part(Shijiazhuang,Hengshui,Baoding,Cangzhou and Langfang)-14.76 mm/10 years,and in the northeastern part(Tangshan)-28.35 mm/10 years,the average precipitation tendency rate of the whole province is-15.28 mm/10 years.In the southern part of Hebei Plain,the temperature tendencies are 0.28 C/10 years,0.32 C/10 years in the central part,and 0.37 C/10 years in the Northeast part,with the average temperature tendencies of 0.33 C/10 years in the whole province.(2)During the summer maize season(June-September)from 1971 to 2018,the average precipitation tendency rate of the whole region was-18.33mm/10 a years,and the average temperature tendency rate was 0.29 ?/10 a years;the accumulative days of three high temperatures(?34 ?,?37 ? and ?40 ?)in the whole region began to show an upward trend,with the tendency rates being 2.36 d/10 a years,0.6 d/10 a years and 0.08 d/10 a years,respectively.The trend of drought and high temperature in summer maize season is obvious.The risk of drought and high temperature varies greatly in different years;the risk of drought and high temperature heat damage is lower in the eastern Hebei plain;the drought risk in the middle and southern plain is worse in the emergence stage and the large mouth stage with time,but the trend of drought risk change is not obvious in the early stage of grouting;the spatial distribution of drought risk in different years is not clear.The accumulated days and effective accumulated temperatures of 32? and 34?,32? and 34 ?have been increasing since the 1970 s,and the probability of high temperature and accumulated temperature are higher in the eastern low plain area.(3)The integrated sowing method of deep-loosening fertilization and poly acrylamide-type water-retaining agent can significantly increase the number of grains per ear,100-grain weight and yield of summer maize,reduce water consumption,and increase WUE,which can achieve better drought resistance and moisture conservation effect;the use of Jade Gold and polyamine plant growth regulators can significantly reduce the length of bald ear tip of maize,increase yield and achieve better results.Resistance to high temperature heat damage.It is suitable for popularization in summer maize production areas of Hebei plain.