Combined Effects Of Controlled-release Pattern And Fertilization Rate On Seedling Quality Of Two Ages Of Chinese Pine

Compared to immediately soluble fertilizer, less information is available on seedling growth and nutrient status in response to a broad range of controlled release fertilizer (CRF) supplies from deficiency to toxicity despite CRF being considered a potential means to optimize nutrient delivery. Although CRF with single and multiple coating layers are widely used in container seedlings, their comparative studies on seedling growth, nutrient storage and especially outplanting performance are lacking. In this study, Pinns tabulaeformis of two seedling ages were fertilized two types of commercial CRF with equivalent formulation and longevity but distinct coating layers at six rates (one-year-old container seedlings at 40,80,120,160,200,240 mg N seedling-1; two-year-old container seedlings at 225,450,675,900,1125,1350 mg N seedling-1). Seedlings were sampled for dry mass, mineral nutrient and non-structural carbohydrate status at the end of growing season, and one-year-old container seedlings were subsequently outplanted for one season. The result showed that:1) One-year-old container seedlings from multiple layers relative to single one had greater starch concentration but reduced dry mass, and N, P, K content and concentration in the nursery, and lower diameter increment in the field. Fertilization rates of 80 and 120 mg N seedling-1 generally yielded maximum plant dry mass and mineral nutrient content; survival peaked at nursery rate of 80 mg N seedling-1 in the field. Toxicity occurred at 200 and 240 mg N seedling-1; growth and starch content and concentration in the nursery concurrent with survival in the field consistently decreased. Therefore, the combination of single layer CRF and 80 mg N seedling-1 (3.3 g CRF per litter media) was recommended to yield optimum nursery and field performance.2) Two-year-old container seedlings from multiple layers relative to single one had greater total and tissue N concentration and total NSC concentration in the nursery. Fertilization rates of 450 mg N seedling-1 generally yielded maximum plant dry mass and starch content and concentration; mineral nutrient content peaked at nursery rate of 675 mg K seedling-1. Toxicity occurred at 1350 mg N seedling-1. Therefore, the combination of multiple layers CRF and 675 mg N seedling-1 (4.5 g CRF per litter media) was recommended to yield optimum nursery performance.Both fertilizer release pattern and fertilization rate were closely associated with seedling age. Therefore, seedling age should be fully considered to develop fertilization regimes.