Early gains from planting large-diameter seedlings and intensive management are additive for loblolly pine

A seedling size/intensive management study with Pinustaeda L. was established in 1993 on two sites in the CoastalPlain of Georgia and South Carolina. Each site contained a 2 × 2split-plot study involving two seedling sizes and two levels ofestablishment intensity. Ideotype ``B' seedlings averaged 5.0 mmin diameter (at the root collar) and were 43 cm tall. Ideotype``A' seedlings averaged 8.5 mm in diameter and were 50 cm tall. ``Standard' establishment practices included herbicides(hexazinone and sulfometuron) and fertilizer (DAP) appliedduring the first year. The ``intensive' management involved twoherbicide applications during the first year and two during thesecond year, fertilizer during the first and third years, andinsecticide applications during the first two years (for controlof tip moth, Rhyacionia frustrana Comstock).Intensive management did not affect survival but planting largerseedlings increased survival slightly on one site. However,treatments affected early growth at both sites. On both sites,fourth-year plot-volumes were increased with greaterestablishment intensity and larger seedlings but there was nointeraction between stock size and establishment intensity. Early growth gains were greatest when both intensive managementand larger seedlings were combined. Depending on site, thiscombination resulted in 21% to 51% more volume (at age 4) thanthe next best treatment (standard seedlings with intensivemanagement).