Sampling and measurement
Plant height (to the top of tassels) and ear height (to the ear-bearing
node) were recorded at silking in five successive plants in the centre
row of each plot. The centre of gravity height (to the balance point of
the above ground plant) was determined at silking and physiological
maturity. Leaf angle (angle between the stem and the line from the leaf
base point to the zenith of the leaf), leaf length, and the distance from
the leaf base point to the zenith of the leaf (h) were recorded when the
leaves were considered to be fully expanded. Leaf area and dry matter
were measured every 30 cm from the ground at silking and maturity in
three successive plants, where ears were classified as the layer in which
they began and all organs were cut off in their natural state in the canopy.
Leaf area was determined using a Portable Laser Leaf Area Analyser
(CI-203; CID Bio-Science, US) and the organs of each layer were separated into the stem, leaf, sheath, tassel, bract, kernel, and cob fractions
and dried at 85 °C to a constant weight. All traits were measured according to standards described in previous study (Subedi and Ma,
2005). The ear ratio was calculated as: