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

Jackson, D. P., Dumroese, R. K., Barnett, J. P., and Patterson, W. B. IN: USDA Forest Service, Rocky Mountain Research Station, Proceedings RMRS- P-50, p. 114-119. National Proceedings: Forest and Conservation Nursery Associations - 2006. 2007.

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 the grass stage.

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Author(s): D. Paul Jackson, R. Kasten Dumroese, James P. Barnett, William B. Patterson

Section: Outplanting Performance