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 i nformation available on the nutrition of the pitch X loblolly hybrid. The purpose of this study was to characterize the temporal variation o f fascicle characteristics and foliar nutrient concentrations of the p itch x loblolly hybrid and compare this variation to that of its paren t species, particularly loblolly pine (Pinus taeda L. The study was lo cated on the Piedmont physiographic province of Virginia. Two plantati ons, Plantation 1 containing full-sib, F1 trees and Plantation 2 conta ining half-sib, F2 trees, were established. Five pitch x loblolly hybr id families, two pitch pine (Pinus rigida Mill.) families, and one lob lolly pine (Pinus taeda L.) family were selected from Plantation 1. Fi ve hybrids, one pitch pine family, and four loblolly pine families wer e selected from Plantation 2. Foliage was sampled monthly from Decembe r 1988 through December 1989, and analyzed for total N, P, K, Ca and M g. Fascicle length, fascicle weight and foliar nutrient data were anal yzed. The hybrids generally had fascicle characteristics intermediate to those of the parent species. Collectively, the various crosses of t he hybrid had foliar nutrient characteristics intermediate between the parent species, with few hybrid nutrient concentrations being signifi cantly different from those of loblolly pine. Loblolly pine critical n utrient concentrations are adequate for diagnosing the nutritional sta tus of most of the hybrid families. Some individual hybrid families ma y not nutritionally emulate loblolly pine and may require the use of i ndividualized critical nutrient concentrations. Hybrid foliage should possibly be sampled in mid-summer to obtain maximum sensitivity to sit e or treatment difference, and in October through December for routine nutrient diagnoses.