Effect of nursery nitrogen application of bare-root Larix olgensis seedlings on growth, nitrogen uptake and initial field performance.

ABSTRACT

Nursery nitrogen application has been used to improve seedling quality. The technique has received little attention with bare-root seedlings and their subsequent field performance on weed competition sites. Our research objective was to examine responses of one- and two- year-old bare-root Olga Bay larch (Larix olgensis Henry) seedlings to nursery nitrogen supplements and subsequent one-year field performance on a competitive site. The fertilizer levels (kg N ha-1) were 0 (control), 60 (conventional fertilization, 60 C), 120 (additional nitrogen applied two times, 120 L), 180 (additional nitrogen applied three times, 180 L) and N were applied in increments of 30 kg ha-1 at 15-day interval to maintain a base nutrient level. Although pre-planting morphological attributes and nitrogen status of one-year-old (1a) seedlings were more sensitive to 60 C than for two-year-old (2a) seedlings, the conventional application failed to enhance their field survival(15.6% vs 17.8%), relative height growth (89.0% vs 79.6%), and relative diameter growth (17.0% vs 22.9%). The 1a seedlings‘ field survival (15.6% for 0, 17.8% for 60 C) and 2a seedlings‘ relative height growth rate (11.0% for 0, 8.9% for 60 C) were not increased significantly until they were provided the 120 L (survival of 23.3% for 1a, relative height growth rate of 15.0% for 2a). According to pre-planting attributes and field performance, optimum nursery nitrogen application was 120 L for the 2a seedlings and 180 L for 1a seedlings. Except for component nitrogen concentration, pre-planting morphological attributes and component N content for the 2a seedlings were as much 3.3 to 37.7 times that of 1a seedlings. In conclusion, the contrasting survival of poor (15.6%-28.9%) for 1a seedlings and high (84.4%-91.1%) for 2a seedlings indicated that additional nitrogen fertilizer would not equal the benefits of an another year‘s growth in the nursery. Successful reforestation could not be fulfilled by 1a seedlings regardless of their pre-nutrients. An alternative technique for sites with competing vegetation was to apply 120kg N ha-1 in the nursery during July and August on 2a seedlings.