Comparison of Site Preparation Methods for Weed Control in Loblolly Pine (Pinus taeda) Plantations

Twelve 20-ha stands of natural loblolly pine (Pinus taeda L.)-mixed hardwoods were harvested and site preparation treatments applied as follows: no site preparation (harvest only); glyphosate [N-(phosphomethyl)glycine] aerially applied at 0.25 kg ai/ha and the site burned 6 weeks later; roller-drum chopped, then burned; sheared and disced in one pass; sheared, then V bladed and disced; sheared, then raked; and sheared, raked, and then disced in three separate passes. Loblolly pine survival was 16% and volume 58% greater after the first two growing seasons on mechanically treated areas than on untreated stands or on areas treated with herbicide and then burned. Total vegetative cover was highest during both growing seasons on sites that had been sprayed and burned, and lowest on sites that were mechanically cleared and tilled. Grass and hardwood cover was negatively correlated with loblolly pine height and seedling volume during both growing seasons.