2.2 Samplings and measurements
In each plot, 20 randomly selected plants were labelled to record tasseling, pollen shedding, silking, and mature date in four experimental years. Plants in a plot were considered to be in a specific phenological stage when 50% of the plants had reached that stage.
All the ears were harvested in two adjacent rows 3 m long in the center section of each plot at maturity stage. Kernel number per ear (KN/ear) was determined by counting row number per ear and kernel number per row. Kernels of these ears were threshed by hand and over-dried at 80 ℃ to constant weight. Five samples of 500 dry kernels were weighed in each plot to determine 1000-kernel weight (TKW). Grain yield (g/ear) was weighed and adjusted to 14% water content.