NURSERY STOCK AND FIELD FERTILISER APPLICATION AFFECT EARLY PERFORMANCE OF PINUS RADIATA ON A PHOSPHORUS-DEFICIENT SITE IN NORTHLAND

An experiment was established on a phosphorus-deficient site to determine the effects of nursery stock type and fertiliser application (after transplanting) on early growth and survival of 1/0 Pinus radiata D.Don seedlings. Three fertiliser treatments were compared: (1) slit-applied diammonium phosphate (DAP; 18 kg N and 20 kg P/ha) at 80 g/tree, (2) Christmas Is. 'A ' grade rock phosphate (RP; 16 % P) broadcast at 50 kg P/ha, and (3) partially acidulated rock phosphate (PARR; 17 % P) broadcast at 50 kg P/ha. Tree stocks given DAP grew best over the first 2 years, but lost the early height advantage in the following 2-year period when stock on PARR- or RP-treated soil outgrew them by c. 0.5 m. After 4 years in the field, the trees with fertiliser were on average 1.8 to 2 times taller than stock without. Container stock maintained its initial 4 cm or so height advantage over bare-root stock for the 4 years of the trial, but cost three times as much to produce. Seedling survival was not affected by fertiliser application after planting, but survival was slightly lower for bare-root seedlings that were initially deficient in nitrogen. Inoculating the soil with freeze-dried spores of Rhizopogon spp. had no beneficial effects on seedling performance