Economic returns from enhancing loblolly pine establishment on two upland sites: effects of seedling grade, fertilization, hexazinone and intensive soil cultivation

The performance of loblolly pines was examined as a function of site preparation and weed control, and fertilization with diammonium phosphate (DAP). The groundline diameter (GLD) of the seedling was also measured, and was identified as the only key variable contributing to fourth-year survival. This survival rate increased from 62% to 83% when the diameter increased from 2.5 mm to 5.1 mm at the Alabama site. A more modest survival rate increase was found at the Virginia test site. Mechanical site preparation was also important in increasing seedling survival. Hexazinone applications increased mortality for late seedlings at all sites, although when combined with DAP fertilization, volume per ha was increased.