Sweetgum Response to Nitrogen Fertilization on Sites of Different Quality and Land Use History

Nitrogen (N) fertilizer management in young hardwood plantations is difficult due to our lack of understanding of the site-specific mechanisms that control tree response. Differences in landuse history and soil characteristics can alter the plant response to added N considerably. Foliage biomass, N content, N concentration, resorption, and soil N supply characteristics were measured on two 4 year-old sweetgum (Liquidambar styraciflua L.) plantations in South Carolina that represent different landuse histories and soil types. Fertilizer responses were much greater overall on a poorly drained pine cutover site compared to a well-drained ag field. Vector analysis and analysis of variance indicated that fertilization increased foliage biomass, N content, N concentration, and leaf area on the cutover site, but only increased foliar N content on the ag site. Foliar responses were negatively related to actual soil N supply, but not potentially mineralizable or total N. N fertilizer recommendations must be site-specific, and an accurate estimate of soil N supply is essential for increasing fertilization efficiency. 1Graduate Research Assistant, Department of Forestry, Virginia Tech, Blacksburg, VA 24060; Forest Nutrition Scientist, Westvaco Forest Science and Technology, Summerville, SC 29484; Professor of Forest Soils, Department of Forestry, Virginia Tech, Blacksburg, VA 24060; Research Scientist, International Paper Corporation, Prattville, AL 36067, respectively. Citation for proceedings: Outcalt, Kenneth W., ed. 2002. Proceedings of the eleventh biennial southern silvicultural research conference. Gen. Tech. Rep. SRS–48. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 622 p.