The Response of Bareroot Loblolly Pine Seedlings to the Amount and Timing of Nitrogen Fertilization in the Nursery

A nursery study was conducted to observe the effects of altering the amount of nitrogen fertilizer at each application on bareroot loblolly pine (Pinus taeda L.) seedling morphology, survival and growth. The treatments were an equal amount of fertilizer applied each time, an increasing amount each time, and a schedule characterized by low amounts, high amounts, and low amounts. Six applications of ammonium nitrate (32.5 percent N) were applied between June and August 2000, and for all treatments, a total of 169 kg N per ha was applied. In addition, for each growing season treatment, the seedlings were treated either in October or November with a one-time application of 56 kg N per ha or 113 kg N per ha as ammonium nitrate. The seedlings were lifted in January 2001, for morphology measurements and field planting. The seedlings treated with an increasing amount of N during the growing season had greater foliage, stem and root weights. Seedlings treated with 113 kg N per ha in October had the largest root collar diameters. First-year survival exceeded 90 percent for all treatments. First-year height growth was greatest for the seedlings that received 113 kg N per ha in October in the nursery