Effects of Container Type, Air Pruning and Fertilizer on the Propagation of Tree Seedlings for Forest Restoration

ABSTRACT: Forests in Thailand are fast disappearing. Recovery of degraded areas can be accelerated by planting native tree species. In order to maximise performance, the highest quality planting stock must be used. Factors which influence seedling production in the nursery include type and size of containers, fertilizer application regime and different techniques of root pruning. The species tested in this study were Artocarpus lakoocha Roxb. (Moraceae), Balakata baccata (Roxb.) Ess. (Euphorbiaceae) and Horsfieldia thorelii Lec. (Myristicaceae). The seedlings were grown in three types of containers: two different sizes of plastic bags 2.5 x 9 in, 3 x 7 in and REX trays (root trainers). Half the containers were raised 45cm off the ground on wire grids, whilst the rest were stood down on the ground. Two fertilizer treatments were applied "Osmocote" (14-14-14) and soluble fertilizer (15-15-15). Performance was determined by measuring height and basal diameter every month for 10 months. At the end of the experiment a sample of seedlings were harvested for examination of root morphology and determination of shoot per root ratio. 

Plastic bags 3 x 7 in with "Osmocote" resulted in the highest quality of seedlings, although REX trays promoted better root morphology than plastic bags and a higher benefit value. There were no significant differences between the two fertilizer treatments in their effects on seedling growth. Deep shade significantly reduced seedling growth.