The effects of sower and bed density on bareroot loblolly pine seedling morphology and early height growthThis article is part of a larger document. View the larger document here.
Precision sowing is commonly used at forest tree nurseries in order to improve the growing space uniformity of seedlings in the beds. Temple-Inland Forest Products Corporation recently purchased a vacuum sower and requested a study be conducted comparing their new sower with a drill sower on the morphological characteristics of loblolly pine (Pinus taeda L.) at lifting. The study was conducted in 2000 and repeated in 2001. The seed were sown using the two sower types to achieve four densities of 161, 215, 269, and 323 seedlings/m2. Two half-sibling families were tested in 2000, and one halfsibling family was tested in 2001. For both studies, the experimental design was a randomized complete block with four replications. Cultural practices used to grow the seedlings were typical for the nursery. The seedlings were hand-lifted mid-winter for measurements of stem height, root-collar diameter, and oven-dry biomass. For the 2001 study, seedlings were handplanted 1 week after lifting in a clearcut near Etoile, TX. The mean morphology of the seedlings was similar when comparing the two sowers. hen averaged for all densities, more seedlings with small root-collar diameters (≤ 3 mm) were sampled in the 2000 study from the drill sower plots than from the vacuum sower plots. For the 2001 study, slightly more seedlings with small diameters were sampled from the vacuum sower plots. At typical operational densities of 215 and 269 seedlings/m2, the use of the vacuum sower resulted in more seedlings at lifting, fewer small-diameter seedlings, and more large-diameter seedlings (≥ 5 mm). As seedbed density was reduced, mean seedling root-collar diameter and oven-dry biomass increased. Seedlings grown in the nursery at 161 seedlings/m2 were taller after the first and second growing season following planting.