Long-Term Effects of Site Preparation Treatments, Complete Competition Control, and Repeated Fertilization on Growth of Slash Pine Plantations in the Flatwoods of the Southeastern United States
Data through age 26 from a well-designed study established in 1979 were analyzed with a repeated-measures analysis of variance approach to evaluate effects of site preparation treatments, complete competition control, and repeated fertilization on growth of slash pine (Pinus elliottii Engelm.) plantations on Spodosols and non-Spodosols in the flatwoods region of southern Georgia and northern Florida. Complete and sustained vegetation control and repeated fertilization consistently and significantly increased slash pine productivity, with greater responses occurring on Spodosols than on non-Spodosols; their combination had less than additive effects on Spodosols and additive effects on non-Spodosols. Complete and sustained vegetation control resulted in greater cumulative responses than repeated fertilization over more than 20 years, and then the gains from repeated fertilization had caught or surpassed the gains from complete vegetation control. Bedding resulted in significant responses in the early ages. Burning improved stand basal area and volume growth rather than average tree height and dbh on non-Spodosols and had little effect on Spodosols. Chopping had no significant effect on either soil group. Results of this study emphasize the need for site-specific silvicultural prescriptions.