Study On Grain Dehydration Characteristics Of Summer Maize In Huanghuaihai Plain

The technology of mechanical grain harvest is a trendency and grain moisture content at harvest is the main factor affecting the quality of mechanical harvest.This harvest technology in China is still in its infancy,which is popular in the Northwest China and Northeast China while in the Huanghuaihai Plain its application just emerged in experimental demonstration.Reducing grain moisture content at harvest is the key to promote this technology.Firstly,a total of 34 mechanical grain harvest trials were carried out in different areas of Huanghuaihai Plain from 2014 to 2016.The grain moisture content and the harvest quality parameters were investigated including the broken rate,the impurity rate,the grain losing rate and ear losing rate.Secondly,a three years' cultivar experiment from 2014 to 2016 and a two years' sowing-date experiment in 2015 and 2016 were conducted to measure the moisture contents of grain,cob,ear-pedicel and bract before and after the physiological maturity.Total 38 cultivars were used in the cultivar experiment.Five sowing dates were arranged in the sowing-date experiment using Zhengdan958 and Xianyu335.The grain dehydration characteristics of summer maize were analyzed.Field experiments were respectively established in 2014 and 2015~2016 at two sites in Beijing and Xinxiang,Henan.The main findings are as follows:1.In Huanghuaihai Plain,the average broken rate was 11.51% and the variation range was 0.34%~51.82%.The main problem of mechanical grain harvest quality was the high broken rate.The grain moisture content was main influencing factor of the harvest quality.The physical and chemical properties of maize grain affected the quality of harvest.There were significant differences in the quality of harvest between different type harvesters and different matters in the same type harvester.2.In Huanghuaihai Plain,the average grain moisture content of summer maize was 27.8% at physiological maturity,and the range was 21.5%~33.1%.The grain moisture content at physiological maturity was affected by genetic factors and environmental conditions,and there was no necessary relationship between the moisture content and the length of grain filling.3.There were siginificant differences between varieties in the grain dehydration characteristics of summer maize.The current varieties can be divided into four types according to the accumulated temperature during grain filling and the grain moisture content at physiological maturity.The first type variety and the second type variety had the shorter filling period and their grain moisture contents were respectively lower and higher.The third type variety and the fourth type variety had the longer filling period and their grain moisture contents were respectively higher and lower.On the basis of this classification,it is expected to screen out the varieties suitable for the mechanical grain harvest technology.4.The bract and the cob moisture contents decreased gradually with the increase of the days after pollination,and their moistures were positively correlated with the grain moisture.The ear-pedicel moisture content decreased slightly with the increase of days after pollination.The length of bract had a significant negative correlation with the grain dehydration rate after physiological maturity,and had a significant positive correlation with the grain moisture content at harvest.The number of grains per spike had a significant negative correlation with the grain dehydration rate before physiological maturity.There was a significant positive correlation between the angle of ear and the grain dehydration rate.The other traits of ear had no significant correlation with the grain dehydration rate.5.The grain weight did not change significantly during the field dry-down after physiological maturity.So the yield loss couldn't caused by the decrease of grain weight after the physiological maturity in Huanghuaihai Plain.