A 2 x 2 factorial experiment was conducted to study the effect of fertilization on Larix olgensis container seedlings. 36.36 or 18.18 mg controlled-release fertilizer (CRF) N and 0 or 1.82 g FM organic amendment (OA) per seedling were applied. There were no significant responses to fertilization in the seedling height, collar diameter, biomass, and potassium (K) uptake. Applying FM OA increased the number of first-order lateral roots with a length > 1 cm (P = 0.040), the tap root length (TRL) (P = 0.012), and the ratio of TRL to seedling height (P = 0.008). Comparing with low application rate CRF N, high application rate CRF N increased the N concentration in root (P = 0.035) as well as the N reserves in stem (P = 0.005), root (P = 0.037), and stem plus root (P = 0.030), and the P reserves in stem (P = 0.047). Applying 36.36 mg CRF N plus 1.82 g FM OA increased the N concentrations in leaf and in stem plus root by 137% (P = 0.040) and 21% (P = 0.013), respectively, and the N reserves in stem (P = 0.020), root (P = 0.017), and stem plus root (P = 0.013). Vector analysis revealed that high application rate of CRF N led to the excess of seedlings N and P, while applying FM OA alleviated the N and P deficiency but led to the K depletion. For nursing L. olgensis container seedlings, a solution of CRF 18 mg N combined with 1.82 g FM OA per seedling was recommended.