| 【Objective】The full mechanization is the direction of modern maize production.Under the current condition,mechanical harvesting,especially the low level of mechanical grain harvesting,is the restriction for the mechanization of maize in China.In this paper,we analyzedthefactors that affected the quality of mechanical by setting different harvesting dates.Establishing the model between grain moisture content and breakage rate and the evaluation method of resistance to breakage with different maize cultivars;Determining the range of grain moisture content that suitable for harvesting and the resistance to breakage of different varieties,which provides supportfor improving the quality and production efficiency of mechanical grain harvesting of spring maize in Northwest China.【Methods】The experiment was conducted in the Xinxiang Comprehensive Experimental Station of the Chinese Academy of Agricultural Sciencesin2017,and the Experimental Station ofChangji and QitaiFarm,Xinjiang in 2018.Among them,the harvest was divided into five phaseswith 28 cultivars in Xinxiang,six phases with 18 cultivars in Changji and five phases with 5 cultivars in Qitai.Simultaneously investigating the mechanical harvest quality(breakagerate,impurity rate and yield loss rate)of each harvest and the grain moisture content,and establishing a quantitative relationship between grain moisture content and indices of mechanical grain quality.With the building of the quadratic curve fitting relationship between grain moisture content and breakage rate of different,theintegral of the fitting lines was calculated between the grain moisture content of 15% to30% and the integral value was used to evaluate the sensibility of grain breakage rate to moisture content of different maize cultivars.【Results】1.Sixharvest times were made from August 28 to October 20 in the Changji Experiment Station,and the grain moisture content of the 18 tested varieties ranged from 12.5% to 39.6%;five harvest times were made from September 22 to October 23 in the Qitai Experiment Station,and the grain moisture content of the 5tested varieties ranged from 15.8%~38.6%.The resultsshowed that in the region of Northwest spring maize,the grain moisture content decreased with the delay of harvest,and the grain breakage rate,impurity rate and grain loss rate were positively correlated with grain moisture content,significantly.The grain broken rate and grain loss rate followed quadratic curve relationship with grain moisture content,and the impurity rate and grain moisture content fitted with exponential function.When the grain moisture content rangedfrom 14.9% to 19.6% and from 12.0% to 23.4% in Changji and Qitai,respectively,the grain breakage rate will be less than 5% and suitable for mechanical grain harvesting.Random factors have a great influence ongrain loss rate.The relationship between grain moisture content andgrainloss rate fitted withquadratic curve in Changji,but no significant correlation was found in Qitai.Samples with a loss rate of ≤5% in Changji and Qitai accounted for 93.4% and 86.7% of the total samples,respectively,and samples with an impurity rate of ≤3% accounted for 84.4% and 90% of the total sample,respectively.Therefore,the loss rate and impurity rate didn’t limit the mechanical grain harvest quality.Varieties and environmental factors will have a significant impact on the quality of mechanical grain harvest.2.The quadratic function fitting was carried out betweenthe grain breakage rate and moisture content of the 42 varieties.The integral value of the curve under 15-30% moisture content was used as the evaluation indicators of breakage susceptibility(BSW)tograin moisture content.The42 cultivars were divided into weak,strong and intermediate types of grain breakage sensitivity.Among the same four varieties in the two places,Lianchuang 825 and Lianchuang 808 were classified intosensitive and fragile varieties,Shandan 650 was classified intointermediate varieties,Zeyu 8911 was classifiedinto weak sensitive and resistantbreaking varieties in Xinxiang and intermediate varieties in Changji.The results of classification in the two regions are generally consistent,indicating that the susceptibility of grain breakage to grain moisture content is a relatively stable genetic character.The cumulative mean deviation between the actual breakage rate of each variety and the theoretical breakage rate of the total equation is used as the evaluation index,andcomparing the classification results of the two evaluation methods.The results indicated that there was no misclassification between varieties with strong and weak sensitivity,and the overall coincidence was high,and the integral method based on the fitting curve of moisture content and fragmentation rate could be used to evaluate the resistance to breakage resistance of varieties.Using the integral method to screen out twelveweak sensitivity to moisture content and resistance-breaking varieties,such as Dika 517,Xindan 65,Shandan 636,Xindan 58,Dongdan 913,Jidan 66,Zeyu 8911,Dika 653,Yudan 9953,Lidan 295,LA505 and Xindan68 in Xinxiang,and sixresistance-breaking varieties in Changji,such as Jiushenghe 2468,Dongdan 6531,Shandan 620,Jiuyu MO3,Tieyuan 24 and KX9384.3.In Changji,through comprehensive evaluation of grain moisture content,yield,maturity and resistance to breakage varieties,Fuyu 1512,Tieyuan 24,Jiuyu M03,KX9384,Zeyu 8911 were screened out for mid maturity cultivars;Jiushenghe 2468,Dongdan 1331 and Dongdan 6531 were screened out for late maturity cultivars,all the above cultivars had good comprehensive performance and were suitable for local mechanical grain harvest.【Conclusion】1.The suitable range of moisture content for mechanical grain harvesting in Changji and Qitai was 14.9%-19.6% and 12.0%-23.4%,respectively.The loss rate and impurity rate didn’t limit the mechanical harvest quality.Varieties and environmental factors have significant impact on the quality of mechanical grain harvest.2.The quadratic curve model of grain water content and breakage rate was established by harvesting in different periods,and the curve was integrated in the range from15% to 30% for the evaluation of breakage sensitivity and tolerance to breakage.Twelve varieties with weak sensitivity and breaking resistancewere screened out in Xinxiang,including Dika 517,Xindan 65,Shandan 636,Xindan58,Dongdan 913,Jidan 66,Zeyu 8911,Dika 653,Yudan 9953,Lidan 295,LA505 and Xindan 68.Six varieties were screened out in Changji,including Jiushenghe 2468,Dongdan 6531,Shandan 620,Jiuyu MO3,Tieyuan 24 and KX9384.3.In Changji,through comprehensive evaluation of grain moisture content,yield,maturity and resistance to breakage,Yuanhua 9,Fuyu 1512,Tieyuan 24,Jiuyu M03,KX9384,Zeyu 8911,Jiushenghe 2468,Dongdan 1331 and Dongdan 6531 were screened out,which had good comprehensive performance and were suitable for local mechanical grain harvest. |
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