Opportunities for Fertilization of Loblolly Pine in the Sandhills of the Southeastern United States

We examined growth responses to fertilization applied one or two times at three Sandhill sites versus annually at the Southeast Tree Research and Education Site (SETRES; and also in the Sandhills) and compared observed responses to the Southwide average response for midrotation fertilization (55 ft3 ac−1 year−1). At sites 1 and 2, average annual volume growth response (AVG) was significantly less (39 and 43%, respectively) than at SETRES, whereas site 3 AVG was similar to that of SETRES. At sites 2, 3, and SETRES, the AVGs of 82, 90, and 128 ft3 ac−1 year−1, respectively, significantly exceeded the Southwide average response of 55 ft3 ac−1 year−1. The diameter class with the most stems per acre at sites 2 and 3 increased 2 in. with fertilization. Resulting diameters were less than chip-n-saw size. Sandhill site fertilization may be appropriate where the superpulp premium is sufficient or wet-condition wood supply is limited. However, given the large Sandhill site fertilizer response, decisions regarding spacing, thinning, product goals, and fertilization become interdependent and require adequate planning to maximize economic return from fertilization. Foliar nutrient concentration assessments were recommended to identify nutrients other than nitrogen and phosphorus that may limit growth when fertilizing Sandhill sites.