Leaf nitrogen concentration based on dry weight (Nw) and leaf area (Na), and chlorophyll meter reading (SPAD) of the wide and narrow sides of leaf blade in the top three leaves at heading stage.

The experiments were conducted in the early, middle, and late growing seasons in Wuxue County and Wuhan City, Hubei Province, China in 2014. Within a row for each leaf position, means followed by different letters are significantly different according to the least significant difference (LSD) at the 0.05 probability level. Leaf nitrogen concentration based on dry weight (Nw) and leaf area (Na), and chlorophyll meter reading (SPAD) of the wide and narrow sides of leaf blade in the top three leaves at heading stage.