Response Of Different Eras Maize Cultivars Lodging Resistance Evolution Law To Subsoiling And Density Increase

At present,the high maize lodging restricted maize yield potential mining and the development of whole mechanization in Inner Mongolia.In this study,maize cultivars released from 1970s-2010s in China were planted at three planting densities(45000 plants ha^-2、75000 plants ha^-2、105000 plants ha^-2).It was to reveal the phenotypic mechanism of lodging-resistant increase with maize cultivars improved through the determination and analysis of maize stalk agronomic and mechanical properties.On this basis,the regulation ranges of different maize cultivars lodging-resistant characters were studied with subsoiling tillage as control means.The main results are as follows:（1）Maize lodging had decreased with cultivars improved.The lodging rate of DH618respectively decreased by 16.06%and 10.94%compared with these of ZD2.The lodging rates of ZD2,DY13 and DY13 were 17.28%,5.87%and 4.81%respectively at 14 days after maturity with subsoiling tillage as control means,which slowed the lodging increase by increasing density.（2）Maize plant height decreased fluctuantly with cultivars improved.The highest was304.19cm for ZD2 and the lowest was 255.78cm for DH618.With improving cultivars,ear height and ear ratio decreased significantly.Compared with shallow rotation and low density,ear height and ear ratio increased on different levels for maize cultivars released of different eras by subsoiling and density increase tillage.The ear height and ear ratio of DY13 and DH618 increased largerly by 22.67 and 16.1 cm,0.07 and 0.07,respectively,which proved the evolution law of ear height and ear ratio for different era cultivars were changed.Ear ratio of DH618 decreased by 0.03 from shallow rotary and high density to subsoiling and high density.（3）The 3rd-5th internodes length decreased with maize cultivars.The 3^rd internode lengths of ZD2,DY13,YD13,XY335 and DH618 were 8.42 cm,8.06 cm,7.42 cm,7.44cm and 6.92 cm,respectively.Their internode lengths increase were differet when they were planted at subsoiling and high density,and the internode length of ZD2,DY13,YD13,XY335 and DH618 increased with 1.76 cm,1.50 cm,2.34 cm,2.17 cm and 2.50 cm respectively.The fourth and fifth internodes were similar to the third internode,but the increase values of old cultivars were greater than these of new cultivars.The 3^rd-5^thinternodes diameter of YD13 was the largest anong these cultivars.The internodes diameter of all maize cultivars decreased on different levels from from shallow rotary and low density to subsoiling and high density.Internodes diameter of DH618 increased from shallow rotary and high density to subsoiling and high density.（4）With the evolution of cultivars,the puncture strength of stalk had no obvious change laws,and the puncture strength of old cultivars was not always lower than that of new cultivars.Compared with subsoiling and high density and shallow rotation and low density,the puncture strength decreasing ranges were different for maize cultivars released from the 1970s to 2010s.The stalk puncture strength of ZD2,DY13,YD13,XY335 and DH618 with sheath decreased by 23.13,13.4,24.1,24.87 and 18.13 N/mm² respectively,while their decrease ranges without sheath were 21.8,14.5,17.5,21.54 and 20.9 N/mm²respectively.With improving cultivars,there was no obvious change in the crushing strength of stalk in different periods.There was no significant difference between the old and the new cultivars,and crushing strength of cultivars released from the 1980s to 2000s tended to increase.Subsoiling and high density reduced maize cultivars crushing strength.The bending strength decreased with cultivars improved.For example,the values of ZD2,DY13,YD13,XY335 and DH618 were respectively 333.99,330.03,333.44,317.99 and290.82 N/mm² at 14 days after maturity.The crushing strength and bending strength of various cultivars were significantly decreased by subsoiling and high density compared with shallow rotary and low density,while the puncture strength and crushing strength of DH618 were significantly increased by subsoiling and high density compared with shallow rotary and high density.（5）Maize yield increased with cultivars improved.The old cultivars yield decreased while the new cultivar yield increased with subsoiling and high density,and the yield increase law was more obvious for maize cultivars released of different years.Correlation analysis showed that reducing ear height and ear ratio could improve maize lodging resistance at different stages,and the puncture strength,bending strength and crushing strength of the third internode were significantly negatively correlated with lodging at silking stage,milk-ripe stage and mature stage.Therefore,the maize cultivars with less than 71 cm ear height and less than 0.28 ear ratio would reduce maize lodging rate,which are suitable for grain dehydration with stalk standing after physiological mature.Subsoiling and reasonable planting density are used accompanying,which would alleviate lodging pressure and obtain high grain yield.