Container Longleaf Pine Seedling Morphology in Response to Varying Rates of Nitrogen Fertilization in the Nursery and Subsequent Growth After Outplanting

A fertilization rate of 2 or 3 mg nitrogen (N) per week for 20 weeks yielded longleaf pine (Pinus palustris) seedlings grown inside a greenhouse that survived well and produced good root collar diameter (RCD) growth the first year after outplanting. Of a range of fertilization rates (0.5 to 4 mg N/week), the 2 mg rate yielded seedlings that did not require needle clipping during nursery production, but increased their RCD by 150% the first year after outplanting. The lower rates (<1 mg N) also survived well, but RCD growth was poorer than the 2 mg rate. In the nursery, the 3 mg rate was borderline for requiring clipping to reduce lodging; under customary nursery practices, the 4 mg rate seedlings would have been clipped; root collar diameter growth in the nursery was similar to that of seedlings grown with the 2 mg N rate. Seedlings receiving >3 mg N also survived well and RCD growth after one season in the field was 14% more than that of the 2 mg N rate. We are continuing to monitor seedlings to determine when they exit