TEMPORAL VARIATION IN FOLIAR NUTRIENT CONCENTRATIONS OF PITCH PINE, LOBLOLLY-PINE AND THE PITCH X LOBLOLLY HYBRID

Although loblolly pine nutrition is well documented, there is little information available on the nutrition of the pitch X loblolly hybrid. The purpose of this study was to characterize the temporal variation of fascicle characteristics and foliar nutrient concentrations of the pitch x loblolly hybrid and compare this variation to that of its parent species, particularly loblolly pine (Pinus taeda L. The study was located on the Piedmont physiographic province of Virginia. Two plantations, Plantation 1 containing full-sib, F1 trees and Plantation 2 containing half-sib, F2 trees, were established. Five pitch x loblolly hybrid families, two pitch pine (Pinus rigida Mill.) families, and one loblolly pine (Pinus taeda L.) family were selected from Plantation 1. Five hybrids, one pitch pine family, and four loblolly pine families were selected from Plantation 2. Foliage was sampled monthly from December 1988 through December 1989, and analyzed for total N, P, K, Ca and Mg. Fascicle length, fascicle weight and foliar nutrient data were analyzed. The hybrids generally had fascicle characteristics intermediate to those of the parent species. Collectively, the various crosses of the hybrid had foliar nutrient characteristics intermediate between the parent species, with few hybrid nutrient concentrations being significantly different from those of loblolly pine. Loblolly pine critical nutrient concentrations are adequate for diagnosing the nutritional status of most of the hybrid families. Some individual hybrid families may not nutritionally emulate loblolly pine and may require the use of individualized critical nutrient concentrations. Hybrid foliage should possibly be sampled in mid-summer to obtain maximum sensitivity to site or treatment difference, and in October through December for routine nutrient diagnoses.