Chlorophyll concentration (g m⁻²), chlorophyll a/b ratio, N concentration (<i>N</i>_a, g m⁻²), and leaf thickness (µm) of the four uppermost leaves of rice plants from three plots not subjected to N application.

Each value is an average of 30 measurements. Within a column, values followed by different letters are significantly different at P <0.05 according to Duncan’s multiple range test. Dates of sampling were DAT 75 in 2008 and DAT 77 in 2009.