Effects Of Nitrogen Fertilizer Management And Chemical Regulation On Lodging Resistance And Yield Formation Of Double-Cropping Rice In Southern Hunan

High yield and lodging resistance are the basic requirements of rice mechanization production.From 2019 to 2020,using early rice Zhuliangyou 819 and Luliangyou 996 and late rice Shengtaiyou 018 and Hyou 518 as materials,set up three different nitrogen fertilizer management modes,N1(basal and tiller fertilizer: panicle fertilizer: grain fertilizer =7:2:1),N2(basal and tiller fertilizer: panicle fertilizer: grain fertilizer =6:3:1),N3(basal and tiller fertilizer: panicle fertilizer: grain fertilizer =5:4:1),paclobutrazol and chitosan oligosaccharides are two chemical regulators,effects of nitrogen management and chemical regulation on yield formation and lodging resistance of double cropping rice in southern Hunan Province.The results are as follows:1.Under N2 mode,at grain filling stage,the plant height was moderate,leaf area index(LAI),leaf SPAD value and population dry matter accumulation were high,moderate tiller number,higher ear-bearing percentage of tillers,spikelets per panicle and seed setting rate were higher,so the yield was the highest.The average of each variety,N2 was 4.5-19.6%higher than N1,and 1.4-13.1% higher than N3.2.Paclobutrazol treatment decreased plant height and dry matter weight of rice,but increased SPAD value at full heading stage and middle grain filling stage,delayed leaf senescence,and was beneficial to photosynthesis of rice.The treatment of paclobutrazol had higher effective spike,lower ear-bearing percentage of tillers,lower spikelets per panicle and seed setting rate,so it had no significant effect on yield increase.chitosan oligosaccharides treatment increased dry matter weight,SPAD value and LAI at full heading stage and middle grain filling stage,as well as ear-bearing percentage of tillers,effective panicle number and seed setting rate,which could significantly increase rice yield.3.Compared to N1 mode,N2 and N3 mode could improve the lodging resistance of rice stems by reducing the height of culm,internode length and height of gravity center and increased the culm diamete,culm wall thickness and internode density,and N2 mode was superior to N3 mode.4.Lodging resistance of rice could be improved by treatment with paclobutrazol and chitosan oligosaccharides,and the effect of paclobutrazol was better,while their mechanism of improving lodging resistance was different.Plobutrazol improved clum lodging resistance by decreasing the height of culm,height of gravity center and internode length,increasing culm diamete,culm wall thickness and internode density,while chitosan oligosaccharides treatment increased clum lodging resistance by decreasing basal internode length and increasing stem diameter and internode density.5.From the interaction effect,N2C1,N2C2 and N3C1 treatments had larger culm diameter and wall thickness,shorter internode length,higher density and lodging resistance and lower lodging index.Leaf area index(LAI),dry matter weight,panicle rate and yield were the highest in N2C2 treatment.In conclusion,N2C2 treatment,that is to say,6:3:1 of ratio of basal and tiller fertilizer,panicle fertilizer and grain fertilizer,and spraying chitosan oligosaccharides at early jointing stage,can improve the lodging resistance of double cropping rice and obtain the highest yield,which is suitable cultivation pattern for double cropping rice in southern Hunan.