Characteristics Of Maize Seed Dehydration And Its Effect On Harvest Quality In Liao River Basin

?Objective?(1)In this study,to solve the problem of high grain moisture during harvest period,the corn seed dehydration technology was popularized in Liao River Basin(LRB).(2)In different maize cultivars,the grain dehydration characteristics and accumulated temperature requirements were studied,the relationship model between grain moisture content and accumulated temperature were simulated.(3)The harvest time of maize grains mechanical harvesting was predicted,according to the variation of accumulated temperature in the LRB.It will provide theoretical basis for rational selection of grain harvesting varieties and estimation of suitable harvesting dates of different varieties in the region,which will have far-reaching significance for effectively improving the quality of mechanical grain harvesting and reducing drying costs in LRB.?Methods?(1)From 2017 to 2018 at Kailu experimental sites in Inner Mongolia Autonomous Region and Tieling experimental sites in Liaoning Province,the dynamic changes of grain moisture content of 30 maize varieties was systematically tested.The grain dehydration-accumulated temperature model of each variety was simulated.The difference of grain dehydration characteristics among eight varieties was analyzed between regions and years.The value of RMSE was calculated for model test.The cumulative temperature from silking stage to physiological maturity stage and the moisture content of grains at physiological maturity stage were used as indicators to classify varieties by two-way average method.Based on the date of spring maize planting in LRB,the accumulated temperature requirement of different varieties at growth stage and grain dehydration was obtained.The accumulated temperature needed accumulate corresponding accumulated days was estimated by historical meteorological data.The date when grain moisture content of different varieties in LRB dropped to the appropriate mechanical grain harvest standard was obtained.(2)Combining the meteorological data of the past 20 years with the suitable sowing date of maize in Tieling experimental site(the date of large-scale sowing of local farmers)and the date of late sowing(the result of data analysis of maize industry system),the required active accumulated temperature of the moisture content of maize grains in different years and varieties was estimated to be reduced to 30%(the upper limit moisture content of suitable mechanical grain harvest),25%(the suitable moisture content of mechanical grain harvest),and 16%(the moisture content of low-moisture grain harvest).The target grain moisture content of different maize varieties in different years was simulated.?Results?(1)Compared with the experimental data of Kailu test site in Inner Mongolia and Tieling test site in Liaoning Province in 2017,there were significant differences in grain moisture content of the same variety during physiological maturity,with variation ranging from 1.1% to 6.1%.Among them,the difference of late-maturing varieties was greater than that of early-maturing varieties.Comparing the data of Tieling test site in 2017 and 2018,the difference of grain moisture content in physiological maturity of the same variety reached a significant level.The difference ranged from 1.2% to 7.5%.The later the maturity of maize varieties,the greater the difference.The variance analysis of accumulated temperature of 8 varieties from sowing to silking,silking to physiological maturity and sowing to physiological maturity in 2017 and 2018 in Tieling and Kailu showed that there were significant differences in accumulated temperature between different varieties at different stages in the same year(P < 0.05).There was no significant difference in accumulated temperature between different regions and stages of the same variety in different years(P > 0.05).The accumulated temperature required from sowing to silking,silking to physiological maturity and from sowing to physiological maturity was relatively stable in different regions and years.(2)The dehydration rate of the same variety varies in different regions and years were differences before and after physiological maturity.In the Kailu and Tieling experimental sites in 2017,the difference of grain dehydration rate between the same varieties before physiological maturity was small,ranging from 0.0015% to 0.004%/?.After physiological maturity,the difference was large,ranging from 0.002% to 0.046%/?.The average grain dehydration rate of Tieling test site before physiological maturity was lower than that of Kailu,and that of Tieling test site after physiological maturity was higher than that of Kailu test site.In Tieling test site in 2017 and 2018,the difference of grain dehydration rate of the same varieties before physiological maturity was small,ranging from 0.001% to 0.003%/?and after physiological maturity was large,ranging from 0.002% to 0.035%/?.The average dehydration rate in 2017 before physiological maturity was lower than that in 2018,and the dehydration rate in 2017 after physiological maturity was higher than that in 2018.Before physiological maturity,the dehydration rate of early sowing was lower than that of late sowing,and after physiological maturity,the dehydration rate of early sowing was higher than that of late sowing.(3)According to the accumulated temperature at grain filling stage and the moisture content of grains at physiological maturity stage,the two-way average method was used to classify different varieties into four types.Among them,early-maturing varieties(II,III)could reduce the moisture content to 28% and 25% in most parts of LRB in mid-late September,including the central part of LRB in Inner Mongolia,the southern part of Liaoning Province and parts of Jilin Province.The moisture content reduced to 28% and 25% of the western part of LRB needs to be delayed to mid-October.For late-maturing varieties(I,IV),the water content in most areas of LRB should be reduced to 28% and 25% in the first and middle of October,while the western area of LRB could not dehydrate to the target water content before November.(4)Under the suitable sowing date and late sowing condition,the date of the same variety and different years falling to the target moisture content was different,and the change range of late-maturing varieties was greater than that of early-maturing varieties.The time when the moisture content dropped to 30% was 10-12 days for early-maturing varieties and 17-21 days for late-maturing varieties.The time when the moisture content dropped to 25% was 13-15 days for early-maturing varieties and 20-30 days for late-maturing varieties.The moisture content of very early-maturing varieties could reduce to 16% before the local latest harvest period.The difference between different years was 15-25 days.?Conclusion?(1)The accumulated temperature of the same variety from sowing to silking,silking to physiological maturity and sowing to physiological maturity had no significant difference in different regions and years,but the moisture content of maize grain had significant difference in physiological maturity.Late-maturing varieties were more different than early-maturing varieties.The dehydration rates of different varieties were different before and after physiological maturation.In different regions and years,the same cultivar also has some differences,which was related to the genetic characteristics and temperature conditions of the cultivar.(2)The spatial distribution characteristics of four types of maize varieties reached the suitable harvesting date of mechanical grains all year round were given by the research,which was helpful to allocate varieties rationally and determine the harvesting time of mechanical grain harvest according to the accumulated temperature conditions in LRB.This could effectively improve the quality of mechanical grain harvest,reduce the cost of drying after harvest,and improve the local corn production and planting benefits.(3)Under the suitable sowing date and late sowing conditions,the date of decreasing the target moisture content in different years and varieties was different.The results showed that the water content of early and middle maturity varieties could be reduced to 30% and 25% at the end of October and the beginning of November.Only Fengken139,A6565,Jingnongke728 and Huamei1 could reduce their water content to 16% in mid-November.Only A6565 could reach 16% moisture content under late sowing conditions.