Nitrogen Use and Cycling during Establishment of Short Rotation Pine.

In order for short rotation pine plantations to be economically and ecologically sustainable it is important that growth be maximized while constraining costs and environmental impacts. The efficient control of competing vegetation and proper nutrient management can facilitate these goals. We utilized eight replicate blocks on the DOE’s Savanah River Site to test two levels of competition control, three levels of fertilizer addition, and two planting densities to determine rates of tree growth and nitrogen cycling. During the first two growing season fertilization did not result in increased growth in young pine, but did result in increased nitrate leaching. Conversely, controlling woody and herbaceous competition in the first two growing seasons effectively increased pine growth. By the third growing season competition control and fertilization effects were evident, and the rate of nitrate leaching decreased significantly. The results indicate that competition control in the first two growing season may free up resources adequate to sustain young pine without additional fertilizer, but as the stand matures increasing N availability increases growth and yield.