Abstract:

The aim of this study was to assess effects of supplemental nitrogen (N) on Olga Bay larch (Larix olgensis) seedlings at late stage of growing season in a nursery. From July to September 2009, the seedlings was fertilized with nitrogen during a period of 2 weeks as follows: control (no fertilization), 60 kg N·hm^-2, (two applications of urea with each 30 kg N·hm^-2), 120 kg N·hm^-2 (four applications), and 180 kg N·hm^-2 (six applications). By the end of growing season, the seedlings fertilized during fast-growing and hardening period had greater shoot biomass, but no significant differences in height, root collar diameter, shoot to root mass ratio, and root biomass in comparison with the control seedlings. Compared to control seedlings, the seedlings fertilized in August and September increased root and shoot N concentrations by 11.5%－15.9% and 6.0%－8.2%, respectively, and the P concentrations by 5.4%－22.9% and 16.7%－22.7%, respectively. In the mid of October, the N concentration increased sharply, while the P concentration declined substantially. This study suggested that P fertilization would be recommended at the late growth period in L. olgensis seedling cultivation to release the decline of the P concentration.

Key words: Larix olgensis, N supply, seedling quality, nutrient concentration