Research Of Lodging Resistance Of Maize During The Late Growth Stage

Mechanical grain harvesting is the developing direction of maize production in China.Unlike traditional manual harvesting and mechanical ear harvesting,the mechanical harvesting of maize grain requires grain moisture contents lower than 25%.In mechanical grain harvesting,maize is generally harvested 2-4 weeks after physiological maturity.During maize grain dehydration via plant standing in the field after physiological maturity,the risk of lodging increases due to stalk senescence or stalk rot.In this study,we investigated lodging indicators included various aspects of maize plant morphology,dry matter,moisture content,anatomical structureand,the mechanical strength of the root and stalk,root morphology,lodging rate,and the quality of maize grain mechanical harvest in different maize cultivars,plant density and inoculation treatment.The effect of lodging on maize grain losing and harvest efficiency in mechanical grain harvest was determined,the main factors affecting the lodging resistance of maize at later growth stage were investigated,the comprehensive indicator for evaluating the lodging resistance of maize was determined,and a device for determining the lodging resistance of maize was developed.The main results are as below.(1)Effect of lodging on maize grain losing and harvest efficiency in mechanical grain harvest.Under natural lodging conditions,the ear loss was a major part of grain yield loss,which increased by 0.15%when lodging rate increased each 1%.The influence of lodging on the ear loss of summer maize in Huang-Huai-Hai region was higher than that of spring maize in north China and northwest China.The harvest speed decreased with increasing lodging rate.Lowering the harvester header and harvest speed can decrease ear loss rate when large area lodging occurs.(2)Effect of natural senescence of stalk on lodging during late growth stage of maize.The increase of stalk lodging rate was the major reason for total lodging rate increase during the late growth stage.Natural senescence of maize during the late growth stage decreased the dry matter and moisture content of stalk,resulting in the decrease of stalk mechanical strength,and the increase of stalk lodging.The stalk lodging rate was more than 5%when breaking force decreased to 14.3 N.There were significant differences in stalk quality reduction and stalk lodging rate among different cultivars.Harvesting at optimal time could prevent lodging after physiological maturity and reduce grain loss in mechanical grain harvest.(3)Effect of stalk rot on maize lodging during the late growth stage.The stalk rot after physiological maturity is an important factor that affects stalk lodging.Stalk lodging increased by 0.14%for each 1%increase in the amount of stalk rot.Inoculated plants had decreased soluble sugar and resulted in a decline in crushing strength.The stalk rot pathogen infected stalks from pith to rind,and the degree of infection gradually increased with increasing days after physiological maturity.(4)The evaluation indicators of lodging resistance were explor to provide the basis for breeding lodging resistance maize cultivars.Modern maize cultivars show no correlation in their resistance to stalk lodging and resistance to root lodging.The ratio of shoot fresh weight to vertical root pulling resistance can be used to determine root lodging susceptibility directly in the field.High ratios indicate a high risk of root lodging.Breeders can improve maize stalk lodging resistance by breeding cultivars with high dry weight per unit length of basal elongated internodes,low ear height,and deep root systems(5)Device for determining critical wind speed of stalk breaking to provide a testing tool for lodging resistance identification.The critical wind speed of stalk breaking can be used to evaluate the stalk-lodging resistance of maize.A new device can be used to measure the critical wind speed of stalk breaking.The device is stable,easy to operate and move and can identify the lodging resistance of maize plants for different varieties and cultivation conditions.With increasing number of days after maize physiological maturity,the critical wind speed of stalk breaking increased first and then decreased,reaching a maximum at 16-24 days after physiological maturity.The critical wind speed is affected by leaf area,fresh weight,stalk tenacity,ear height.