Abstract: 【Objective】To provide data support for the evaluation of maize varieties suitable for mechanical grain harvest in Inner Mongolia,and to provide a reference for maize variety selection and timely harvest.【Methods】In the experiment,the representative maize varieties of extremely early,early,middle early,middle,middle late,and late maturity groups were used as experimental materials,and the mechanical grain harvest characters were studied in seven maize planting areas in Inner Mongolia. At physiological maturity,10,20 and 30 days after physiological maturity,the plant lodging rate,grain moisture content,grain breakage rate,grain fragmentation rate,impurity rate,and other indicators were measured. The yield of 60 000, 75 000,90 000 and 105 000 plants/hm² were compared by using the varieties suitable for mechanical grain harvest in Inner Mongolia.【Results】The plant lodging rate showed increasing trend with the increase of the number of days after physiological maturity. Grain moisture content and dehydration rate showed decreasing trend with the increase of the number of days after physiological maturity. The grain breakage rate,grain fragmentation rate and impurity rate decreased with the increase of the number of days after physiological maturity. The relationship between grain breakage rate,grain fragmentation rate, impurity rate and grain moisture content was unary quadratic curve. When the grain moisture content was 16.1%,17.0% and 15.6%,the corresponding grain breakage rate,grain fragmentation rate and impurity rate were the lowest,which were 1.3%,1.1% and 0.6% respectively. The relationship between dehydration rate and daily average temperature was a unary quadratic curve,when the daily average temperature was 0-5 ℃,the dehydration was slow,and the daily dehydration was 0.197-0.211 percentage points. The accumulated temperature from physiological maturity to grain moisture content reduced to 25.0% was 100-200 ℃. The suitable planting density of the varieties suitable for mechanical grain harvest in each region was 90 000 plants/hm².【Conclusion】The evaluation index of maize suitable for mechanical grain harvest as follows：The suitable planting density was 90 000 plants/hm²,and during the harvest,the suitable harvesting time was 10-20 days after physiological maturity with plant lodging rate≤5.0%,grain moisture content≤25.0%,grain breakage rate≤5.0%,grain fragmentation rate≤2.0%,impurity rate≤1.1%,yield loss rate≤5.0%.

Key words: Maize, Mechanical grain harvest, Grain moisture content, Harvest quality, Suitable mechanical grain harvest period