Nitrogen Fertilization Strategies in a Short-Rotation Sycamore Plantation

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Forest Ecology and Management







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This study evaluates the effect of different nitrogen fertilization regimes in an American sycamore (Platanus occidentalis L.) plantation on tree growth, fertilizer recovery by the trees, and nitrate leaching from the soil with the objective of determining the optimum application regime. A total of 450 kg N ha−1 was added as urea over a 3 year period at the following rates: a single dose shortly after planting (O1); 150 kg N ha−1 applied once every year (AE); applications of 50 kg N ha−1 three times per year (P); annual doses that increased with tree growth (AB: 50, 150, and 250 kg N ha−1). Aboveground biomass production, N accumulation in biomass, and soil solution chemistry were measured between 1989 and 1992 in three replicate plots per treatment and compared with those in unfertilized control plots. The O1 fertilization was inefficient because growth benefits were short-lived and were associated with excessive NO3 leaching losses in the first year. Multiple fertilizer applications generally resulted in better growth, while soil solution NO3 levels depended on the actual rate and frequency of fertilization. Nitrate leaching was greatest in the AE plots. The AB treatment, in which annual N additions increased commensurate with tree size, was optimum in terms of enhancing stem biomass production and reducing potential groundwater contamination. The reduction in fertilizer use efficiency and the increase in NO3 leaching in the third year indicate that the input of 250 kg N ha−1 exceeded tree N retention capacity and should have been reduced to approximately one-half that rate. Increasing the frequency of fertilization from once per year to three times per growing season also decreased NO3 leaching losses (i.e. improved N recovery) without measurable benefits to biomass production, and may therefore not be cost-effective in commercial operations.


Originally published by Elsevier. Publisher's PDF available through remote link.