Data collection
Plants were harvested at 30, 50 and 70 d of plant 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 plant, the following traits were measured if applicable: the length of stem, diameter at the basal of stem, petiole length and angle, leaf number, lamina width (lamina size), branch length, angle and number, main root length, main root diameter, lateral root length and lateral root number (above or equal to 1 mm in diameter along the main root). Morphological traits of plants at 30 d of growth were not taken into account due to small plant sizes. Each individual plant was then separated into root, stem, petiole, leaf, reproductive and branch parts if any, oven-dried at 75oC for two days and weighed.