Study on the Dehydration and Mechanical Characteristics of Summer Maize Grains and Cobs under High-Density Planting
This study aims to investigate the variation of grain and cob dehydration and mechanical characteris-tics in determining suitability for grain-harvesting of summer maize under high-density planting,and to analyze the relationship between moisture content and mechanical strength.A field experiment was conducted using Zhongyu3(ZY3)and Zhenghong6(ZH6)with two planting densities of 67 500 plant/ha and 82 500 plant/ha.The results showed that,with the increased of planting density,maize grain and cob moisture content showed a trend of increase,dehy-dration rate and mechanical strength showed a trend of decrease.Among the two cultivars.ZY3 exhibited the better mechanical harvesting properties with a lower stalk lodging rate and the accumulated temperatures from silking to the time reaching grain moisture of 28%and 25%(suitable for mechanical grain harvesting)were lesser than ZH6,the grain crushing strength(CS)and puncture strength(PS)were significantly higher than ZH6,and the cob bending strength(BS)was significantly lower than ZH6,and their effect of genotype variety were larger than planting density.Correlation analysis showed that CS,PS and BS were significantly and negatively correlated with grain and cob mois-ture content,BS was significantly and positively correlated with cob dry weight,dry weight per unit length and dry weight per unit volume,in contrast,BS was significantly and negatively correlated with cob length,and the ratio of length to diameter.There was no significant difference between planting density and cultivar of maize yield,but along with the increasing of planting density,the stalk lodging rate of summer maize increased significantly,the de-hydration rate of ZY3 was significantly decreased after physiological maturity,and the accumulated temperatures from silking to the time reaching grain moisture were increased.
Summer maizeHigh-density plantingGrain and cobDehydration characteristicMechanical strength