Total, and chemical fractions, of nitrogen and phosphorus in Eucalyptus seedling leaves: Effects of species, nursery fertiliser management and transplanting

Total and nitrogen (N)- and phosphorus (P)-containing chemical fractions extracted in trichloroacetic acid (TCA) were assessed after nursery production (pre-planting) and during establishment of E. globulus Labill. and E. nitens (Deane and Maiden) Maiden seedlings in the field and following transfer of E. nitens seedlings from warm temperatures in a nursery to cool temperatures in a growth chamber. In field experiments, seedlings of both species were transplanted in spring onto a site at 350 m above sea level (asl) and E. nitens in early winter onto a site at 700 m asl. E. nitens seedlings received either high- or low-nutrient, treatments in the nursery before planting at 700 m asl or before transfer to the growth chamber. E. globulus had greater foliar concentrations of total N and P at planting than E. nitens after nursery production under the same fertiliser regime. In both field trials and the growth chamber experiment a decrease in N, and generally P, concentration in the leaves was observed between pre-planting and the first post-planting measurement. Decreased N was observed after a period of one week and 15 weeks at 350 and 700 in asl, respectively. E. globulus seedlings had higher concentrations of insoluble P complexes and lower concentrations of inorganic P than E. nitens. Increased levels of soluble N across treatments were associated with warm spring temperatures in both field experiments. N and P concentrations with time during establishment were similar in all experiments. This may be related to retranslocation associated with growth after transplanting. Despite differences in N and P concentrations, partitioning of total N to soluble (nitrate, ammonia and amino acid), nucleic acid and protein N and of total P to nucleic acid, sugar, inorganic and insoluble P were similar between E. nitens high- and low-nutrient treatments, and with time during establishment. The TCA method yielded insights additional to those of total N and P. This study showed that the plant nutrition associated with eucalypt seedling transplanting is highly dynamic and complex.