Characterizing fertility targets and multi-element interactions in nursery culture ofQuercus rubraseedlings

We quantified and characterized fertility targets for nursery culture of container northern red oak (Quercus rubra L.) seedlings. Plants were supplied with a 15N-5P 2 O 5 -15K 2 O fertilizer at eight rates ranging from 0-150 mg N plant -1 and reared for 18 wk in a greenhouse. Plant growth and nutritional response to increased fertilization followed a curvilinear pattern depicting phases that ranged from deficiency to toxicity. Seedling dry mass production was maximized at sufficiency (25 mg N plant -1 season -1 ) while optimum N and P uptake occurred at 100 mg N plant -1 season -1 . The 150 mg N plant -1 seasonal dose rate induced N and P toxicity, but resulted in antagonistic K interaction. Nutrient loading raised plant N and P contents by 27 and 55%. This new approach demonstrates promise to help refine fertility targets for nursery production of Q. rubra planting stock and may have application to other hardwood species or cultural systems.