| Maize is one of the important food crops in China,it plays an important role in the food security and economic development of the country.Harvest is the key link of maize production,which consumes large labor and increases the cost of corn production.The mechanical harvest kernel is beneficial to the development of maize whole-process mechanization,improve maize harvest efficiency and promote the development of rural economy.However,the grain moisture content of maize is too high,causes a high grain crushing rate,reduces grain quality,and is not conducive to storage,processing and transportation.The experiment was conducted in teaching and experiment station of Hebei Agricultural University during 2016 and 2017.Five maize varieties were used as materials,and 3 planting densities of 60000,75000 and 90000 plants per hectare were set in the experiment.The change rules of dry matter accumulation,lodging resistance,kernel filling dehydration characteristics,yield and accumulated temperature requirements of different maize varieties were studied.The research results provided a theoretical basis for selecting maize varieties that were early maturity,high yield,high density,lodging resistance and suitable for mechanical kernel harvest.The main results of this experiment were as follows:1.The maximum kernel filling rate of early maturing varieties Xiangyu 790 and Shandan 638 compared with the control variety Zhengdan 958(CK)were reduced by 24.0% and 20.7%,respectively,and the kernel filling active period decreased by 5.8d and 4.3d,respectively,100-kernel weight decreased by 27.4% and 21.8%,respectively,yield decreased by 39.1% and 25.2%,respectively.Therefore,mechanical harvest maize varieties should properly increase density in order to increase yield.2.The maximum dehydration rates of early maturing varieties Xiangyu 790 and Shandan 638 were 43.7% and 31.5% higher than that of Zhengdan 958 respectively,and the kernel dehydration time after physiological maturing were 15 d and 9d longer,grain moisture content at harvest were reduced by 30.4 % and 16.0%.Grain moisture content had a highly significant positive correlattion with moisture content of husk,cob,ear sheath,ear leaf,and had a significant positive correlation with moisture content of ear internode.Grain moisture content had a significant positive correlattion with husk length and number.Therefore,mechanical harvest maize varieties should have the characteristics of high kernel dehydration rate,long time dehydration after physiological maturity,and low moisture content at harvest.3.The puncture force of internode of mid-late maturing varieties Lishou1 increased by 4.1% compared with Zhengdan 958,the compressive force increased by 10.9%,the lodging resist force increased by 12.1%,and the field lodging rate decreased by 5.6 percentage points.There was a highly significant negative correlation between field lodging rate and puncture force and compressive force,and a significant negative correlation with lodging resist force.Therefore,mechanical harvest maize varieties should have the characteristics of good tightness and strong stem strength.4.The annual effective accumulated temperature(GDD10)of the maize growth period in the summer maize area of Hebei province from June 15 to October 5 is 1602.1?·d-1738.7?·d.In short effective accumulated temperature years,mid-late maturing varieties Zhengdan 958 and Lishou 1 can not reach physiological maturity at harvest.The early maturing varieties Xiangyu 790 and Shandan 638 were 7d and 2d earlier than Zhengdan 958,and the growth period was earlier 15 d and 9d,respectively,and the effective accumulated temperature decreased by 9.2% and 4.8%.In the summer maize area of Hebei province,where light and heat resources are limited,early maturing varieties are more suitable for mechanical harvest than mid-late maturing varieties. |
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