Nitrogen fertilizer application is an important measure to obtain high and stable corn yield, and the moisture content of corn grains is an important factor affecting the quality of mechanical grain harvesting.  In this study, four different nitrogen fertilizer treatments from 0 to 450 kg ha^–1 pure nitrogen were set for a planting density of 12.0×104 plants ha^–1 in 2017 and 2018, and 18 different nitrogen fertilizer treatments from 0 to 765 kg ha^–1 pure nitrogen were set for planting densities of 7.5×10⁴ and 12.0×10⁴ plants ha^–1 in 2019, to investigate the effect of nitrogen application rate on the moisture content of corn grains.  Under each treatment, the growth of corn, leaf area index (LAI) of green leaves, grain moisture content, and grain dehydration rate were measured.  The results showed that, as nitrogen application increased from 0 to 765 kg ha^–1, the silking stage was delayed by about 1 day, the maturity stage was delayed by about 1–2 days, and the number of physiologically mature green leaves and LAI increased.  At and after physiological maturity, the extreme difference in grain moisture content between different nitrogen application rates was 1.9–4.0%.  As the amount of nitrogen application increased, the corn grain dehydration rate after physiological maturity decreased, but it did not reach statistical significance between nitrogen application rate and grain dehydration rate.  No significant correlation was observed between LAI at physiological maturity and grain dehydration rate after physiological maturity.  In short, nitrogen application affected the grain moisture content of corn at and after physiological maturity, however, the difference in grain moisture content among different nitrogen application rates was small.  These results suggest that the effect of nitrogen application on the moisture content of corn grains should not be considered in agricultural production.

The accurate evaluation of maize stalk lodging resistance in different growth periods enables timely management of lodging risks and ensures stable and high maize yields.  Here, we established five different sowing dates to create different conditions for maize growth.  We evaluated the effects of the different growth conditions on lodging resistance by determining stalk morphology, moisture content, mechanical strength and dry matter, and the relationship between stalk breaking force and these indicators during the silking stage (R1), milk stage (R3), physiological maturity stage (R6), and 20 days after R6.  Plant height at R1 positively affected stalk breaking force.  At R3, the coefficient of ear height and the dry weight per unit length of basal internodes were key indicators of stalk lodging resistance.  At R6, the key indicators were the coefficient of the center of gravity height and plant fresh weight.  After R6, the key indicator was the coefficient of the center of gravity height.  The crushing strength of the fourth internode correlated significantly and positively with the stalk breaking force from R1 to R6, which indicates that crushing strength is a reliable indicator of stalk mechanical strength.  These results suggest that high stalk strength and low ear height benefit lodging resistance prior to R6.  During and after R6, the coefficient of the center of gravity height and the mechanical strength of basal internodes can be used to evaluate plant lodging resistance and the appropriate time for harvesting in fields with a high lodging risk.