Effects of nursery management practices on morphological quality attributes of tree seedlings at planting: The case of oil palm (Elaeis guineensis Jacq.)

Abstract

Even though oil palm production is associated with forest clearance and environmental degradation, it is also considered a potential carbon sink. For oil palm to fulfil its potential role in environmental sustainability, high quality seedlings are required. Nursery managers in Benin who produce oil palm seedlings for owners of small farms ignored recommended practices and developed their own. To evaluate the efficacy of their nursery management practices in terms of seedling growth, 2 experiments were conducted. Three polybag sizes (5L, 8L, and 15L) in combination with 4 types of soil substrates and 3 fertiliser treatments were implemented in both experiments in a factorial design. Biomass (shoot, root, shoot-to-root ratio) and allometric (seedling height, number of leaves, length of most developed leaf, root-collar diameter) variables were measured 8 or 6months after transplanting.Polybag size was the main factor determining oil palm seedling growth in both experiments. Applying 10g fertiliser once a month was harmful to seedling survival with lethal effects in 5L polybags. Arable soil with animal manure in 8L polybags without any fertiliser supply sustained seedling growth well; this practice seemed to be the best balance between quality and production cost although 15L polybags produced the best seedlings. Growth variables were highly correlated. Height and root-collar diameter constitute good candidates to estimate seedling biomass production non-destructively. The treatment effects on total biomass produced were similar for the 2 experiments.Given the observed large effects of polybag size on seedling growth, our findings suggest that fertiliser addition or substrate selection cannot overrule container size effects; the latter should be considered carefully for (forest and crop) tree seedling production in nurseries.