[Objective] In Huang-huai-hai Plain,the earlier harvesting date and the higher grain moisture content of summer maize reduces the harvest quality of mechanical grain harvest technology.The delayed harvest can reduce the grain moisture content.It remains unknown whether the grain weight and the yield will decrease or not during the field drying process.Clearing the changes of maize grain moisture and grain weight after physiological maturity is of benefit to promoting the application of grain mechanical harvesting technology.[Method] In 2015 and 2016,twenty two mainly planted cultivars were investigated in Comprehensive Experiment Stations of Chinese Academy of Agricultural Sciences located in Xinxiang,Henan.Controlled pollination was applied in every cultivar.In 2015,from the 26th day after pollination to the 26th-52th day after physiological maturity,the grain weight and grain moisture were measured to analyze their changes.In 2016,the same traits were measured from the 11th day after pollination to the 16th-35th day after physiological maturity.[Result] Results showed that the average 100-kernel dry weight was 30.8 g at physiological maturity ranging from 23.3 g to 37.4 g.The average kernel moisture content was 27.5％ at physiological maturity ranging from 21.5％ to 33.1％.When all cultivars were finally tested after the long drying-down in field,the average 100-kernel dry weight was 32.0 g ranging from 22.9 g to 38.4g and the average kernel moisture content was 17.3％ ranged from 12.9％ to 24.4％.Before physiological maturity,the kernel weight increased significantly with the days after pollination.After physiological maturity,the kernel moisture content reduced significantly while the kernel weight kept stable.There was no statistically significant correlation between the kernel moisture content and the kernel weight after physiological maturity.[Conclusion] In Huang-huai-hai Plain,during the drying-down in field,com kernel moisture content reduced significantly after physiological maturity while kernel dry weight was stable.The delayed harvest is of help for lower kernel moisture content and can't decrease the yield due to the loss of kernel weight.

This study was conducted to investigate the effects of nitrogen top dressing time on yield and quality in wheat with different types of grain color.The cultivars were white wheat(Jindong8 and Wanmai38),black wheat(Luozhen1 and KZ6061),and green wheat(Lvmai1 and Lvmai2),Black wheat and green wheat had pigment in endosperm and seed coat.The results showed that,comparing to nitrogen applied at the 2 leaf stage,nitrogen applied on the 5 leaf stage resulted in higher protein content.The protein content was significantly higher in color wheat than in common white wheat.Nitrogen application at late stages of wheat growth could magnify the differences of the protein content between colored wheat and common white wheat.Nitrogen applied at late stages enhanced protein contents in wheat with black and green colored grain.No difference was found on the effects of nitrogen top dressing time on the processing quality between different varieties.Nitrogen applied on the 5 leaf stage resulted in better processing quality than on the 2 leaf stage.The differences of development and stability time resulted from N applied time between two treatments were not significant.Sedimentation volume and gluten content were higher in color wheat than in white wheat.Processing quality in black wheat was better than that in green wheat.Consequently,nitrogen applied strategies were rather more important to improve processing quality of black wheat.Grain yield in color wheat was lower than that in white wheat,but higher than green wheat.Yield in green and white wheat showed a relative larger response in green and white color wheat than black one.

Strong gluten wheat cultivars Jimai 20 was used to study the physiological indexes,yield and some quality characteristics at different nitrogen topdressing stages.The results indicated that nitrogen topdressing stage could regulate protein content,grain yield and some physiological indexes of flag leave under the condition of the total amount of nitrogen application of 270 kg/ha and the ratio of base and topdressing of 5∶5.Nitrogen application at late stage of wheat development,especially at the flowering stage,could suppress chlorophyll's degrading,keep the activity of nitrate reductase(NRA) at high level,prolong the functional stage of leaf.There was a linear relationship between NRA and grain protein content during 14～21 days after flag leaf spreading.The correlation between chlorophyll content and grain yield was significant at the same time.Crude protein content increased with delaying of topdressing nitrogen and reached maximum at the flowering stage.Moreover,the contents of protein component increased with delaying of nitrogen top dressing stage,and the maximum value appeared at the three late stages.In this experiment,grain yield and protein yield were high in the treatment of nitrogen application at the flowering stage.Overall,for strong gluten wheat,the best stage of nitrogen topdressing that could coordinate the quality with yield was the flowering stage.

2005—2006年小麦生长季,利用7个强筋品种,按统一设计方案分别在7个省进行田间试验,研究灌水在不同生态环境下对籽粒产量和蛋白质含量及其稳定性的调控效应。结果表明,在小麦生育期平均降水量低于常年的情况下,各试验点的平均产量以灌3次水（灌水时期分别为春2叶露尖、春5叶露尖和开花期,每次灌水量均为600m3hm-2）的处理最高,显著高于灌2次水（灌水时期为春5叶露尖和开花期,每次灌水量均为600m3hm-2）和灌1次水（灌水时期为春5叶露尖期,灌水量为600m3hm-2）的处理,但与灌4次水（灌水时期分别为春2叶露尖、春5叶露尖、开花期和灌浆期,每次灌水量均为600m3hm-2）的处理差异不显著。随着灌水次数和灌水量的增加,各试验点总体呈现产量提高和试验点间差异缩小的趋势,产量环境指数越低的试验点,灌水处理的增产效果越好。说明灌水可使不同生态环境下强筋小麦产量的稳定性增强。平均产量越高的品种,在各试验点间的产量变异越小,即稳定性越好;产量的环境指数越高,品种间产量变异系数越小。不同灌水处理的籽粒蛋白质含量差异显著,随灌水次数增加,平均蛋白质含量有逐渐降低的趋势,但在降水过少的河北任丘试验点,增加灌水使蛋白质含量有所提高。同一品种在不同试验点的蛋白质含量有较大变化。在各试验点间变异系数小的品种,其蛋白质含量静态稳定性较好;而变异系数大的品种则对生态环境变化有较大反应,说明其品质的栽培可塑性较强。