| Due to its high density,mechanized harvest maize faces greater risk of lodging.The area of mechanized harvest summer maize in Dongting Lake region of Hunan province is gradually expanding.In order to define the best chemical control mode of mechanized harvestsummer maize in this region and achieve the goals of high yield and lodging resistance,field tests were carried out in Taoyuan county,Hunan province in 2020-2021using Zhengdan 958 as material.Under the condition of high density(90,000 plants/hm~2),the effects of chemical control agents(amine·ethephon,V1;Guoguangyiling,V2),spray site(whole plant,P1;Leaf,P2),spraying stage(6-leaf,C1;12-leaf,C2;6-leaf+12-leaf,C3)on yield components and lodging resistance of summer maize and their interaction were comparatively studied.The main results showed that:(1)Leaf area index(LAI)of summer maize at 12 leaf stage,silking stage and 20 days after silking showed a trend of C2>C1>C3,V2>V2 and P2>P1,among which spraying stage had a significant effect.Spraying stage and location had significant effects on dry matter accumulation of summer maize,and the three factors had obvious interaction effect,and the dry matter accumulation of C1V2P2,C1V1P2,C2V1P2 and C2V2P1 treatments was higher.(2)Among the three factors,only the spraying stage had a significant effect on the yield,and the yield showed a trend of C1>C2>C3,that of C1 was 1.7-7.0%higher than that of CK,and that of C3 was significantly lower than that of C1 and CK.The maximum yield in two years was 8793.7 kg/hm2 and 10341.3 kg/hm2 under C1V2P2 treatment,respectively.The interaction between chemical control agent type and spraying stage and three factors had a significant effect on yield,and C1V2P2 had the best yield increase effect,followed by C2V2P2,and the two treatments had no significant difference.Correlation analysis showed that chemical regulation affected summer maize yield mainly by affecting grain number per ear.(3)The type of chemical control agent and application stage had significant or extremely significant effects on plant height and panicle height.Each chemical control treatment could significantly reduce plant height and panicle height,and the decreasing range showed the trend of C3>C2>C1,P2>P1,V1>V2,among which C2 and C3 treatments decreased significantly compared with CK.Correlation analysis showed that plant height was significantly positively correlated with dry matter accumulation and actual yield.(4)The stem diameter showed the trend of V1>V2,C2>C1>C3,and the three factors had a significant interaction effect on stem diameter in 2020.The interaction between spraying site and spraying stage had significant effect on stem diameter at maturity stage in2021,and C1V1P1 treatment was the largest in both silking stage and maturity stage,followed by C1V1P2 and C1V2P2 treatment.(5)The number of aerial roots under chemical control showed the trend of V1>V2 and P1>P2.By analyzing the interaction effect of the three factors,the number of layers and roots in C3V1P1 treatment was significantly higher than those in other treatments,while the number of layers and roots in C3V2P2 treatment was significantly lower than those in CK.(6)All chemical control treatments could significantly improve the stem compressive breaking strength at maturity,and C2V1P1 and C2V2P2 treatments had higher compressive breaking strength.The tensile breaking force of C2 treatment was larger than that of C2treatment,and the effect of spraying site,spraying period,chemical control agent type and spraying site on stem tensile breaking force was significant.No lodging and folding occurred in all treatments in the two-year experiment field.Comprehensive consideration of yield and lodging resistance,the present study concluded that spraying Guoguangyilingon leaves at 6-leaf stage(C1V2P2)and spraying Guoguangyiling at 12-leaf stage(C2V2P2)were suitable for chemical control of summer maize in Dongting Lake area. |
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