Outplanting performance of Pinus patula Schltdl. & Cham. as an effect of root pruning and containers used in the nursery

Introduction: The production of seedlings in containers implies the risk of deforming the root. This damage persists and increases after outplanting causing negative effects on the plants. Objective: To evaluate outplanting performance of Pinus patula Schltdl. & Cham. as an effect of root pruning and containers used in the nursery. Materials and methods: Nine-month-old seedlings were grown in three 170 cc containers: plastic tray, polystyrene tray and grid with containers with 54, 77 and 42 cavities, respectively. The cavities were impregnated with copper hydroxide to encourage chemical root pruning; additionally, an aerial root pruning treatment was included (containers with lateral openings). Survival and growth of P. patula were evaluated under field conditions during two years in 72 plants per treatment, randomly distributed in six blocks or replications. Results and discussion: Pruned and unpruned plants showed significant differences (P ≤ 0.05) in survival (89 vs. 79 %), height (154.0 vs. 147.1 cm) and relative annual growth rates of diameter (0.97 vs. 0.93 cm·cm-1·year-1) and height (0.97 vs. 0.92 cm·cm-1·year-1). Plants in plastic containers and polystyrene trays had the best growth and survival rates. The interaction container*pruning was not significant. In spite of starting with the lowest sizes, the plants in containers designed for aerial root pruning had similar characteristics to those grown in the same containers with and without chemical root pruning. Conclusion: Root pruning favored survival and growth of P. patula after outplanting and had a greater effect than the type of container used.