Nine-Year Growth Responses to Planting Density Manipulation and Repeated Early Fertilization in a Loblolly Pine Stand in the Virginia Piedmont

Achieving maximum stand leaf area early in the rotation can have large positive effects on plantation productivity. Two silvicultural management strategies that can enhance leaf area development are increasing planting density and improving nutrition. A trial was established to determine how these two silvicultural management strategies affect the growth of Pinus taeda L. in the Virginia Piedmont. The study was designed as a factorial with two planting densities (363 and 726 trees ac(-1)) and three levels of nutrient additions. The three nutrient levels were aimed at maintaining the current site index (SI(25)) of the stand (55 ft) or improving the SI(25) to 70 and 80 ft. None of the treatments affected survival or height during the first 9 years. At age 9, the lower stand density treatment had a greater average diameter (6.03 in.) compared with the high stand density treatment (5.10 in.) averaged across all nutrient levels. The intermediate and high nutrient treatments increased diameter by 0.21 and 0.35 in., respectively, compared with the low nutrient treatment (5.38 in.), when averaged across both stand densities. Intraspecific competition affected diameter growth from age 5, whereas nutrient additions increased growth from age 4.