Data collection
Plants were harvested at 30, 50 and 70 d of growth, representing
developmental stages of early vegetative growth, late vegetative or
early reproductive growth, and middle to late reproductive growth
respectively. At each stage, six individual plants were randomly chosen
from each plot, making a total of 6 replicates × 3 plots × 3 densities ×
2 soils × 3 stages = 324 samplings. For each individual plant, the
following traits were measured if applicable: diameter at the basal of
the main root, length and number of lateral roots (above or equal to 1
mm in diameter along the main root). Morphological root traits were not
measured at 30 d of growth due to small sizes of plants. Each individual
was then separated into roots, stems, petioles, leaves, reproductive
organs and branches (if any), enveloped respectively, and oven-dried at
75 oC for 2 d and weighed.