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Keywords: nursery operations
nursery fertilization
tree morphology
tree physiology
growth
Abstract: Three months following sowing, Douglas-fir (Pseudotsuga menziesii (Mirb.)
Franco) seedlings were transplanted into pots with controlled-release fertilizer (CRF) applied at
rates of 0, 8, 16, and 24 g/2200 cm3 soil as a single uniform layer beneath the root system.
Seedlings were destructively harvested periodically, and roots were divided into vertical segments
above (S1), within (S2), and below (S3) the fertilizer layer. Two months following transplant, the
number of active root tips was positively correlated with CRF rate in S1 and negatively correlated
with rate in S2 and S3. At 6 months, root penetration into S3 was severely restricted at 16 and 24
g. This was attributed to detrimental changes in soil osmotic potential in S2. Fertilizer improved
seedling growth at 8 g after 6 months compared with controls but was inhibitory at 24 g.
Photochemical quantum yield was higher in all CRF treatments compared with controls 3 months
following transplant, which corresponded with rapid initial CRF nutrient release. Despite
improvements in nutrient release technology with CRF, high application rates may result in
excessive concentrations of fertilizer nutrients in media, which can restrict root penetration and
negatively affect seedling growth. Conservative application rates and improvements in CRF
technology will help reduce the potential for adverse effects on seedling development.
285. Jacobs, D.F., R. Rose, D.L. Haase and P.D. Morgan. 2003b. Influence of nursery soil
amendments on water relations, root architectural development, and field performance of
Douglas-fir transplants. New-Forests 26(3): 263-277.
Keywords: nursery operations
fertilization
tree physiology
tree morphology
growth
carbon allocation
soil properties
tree/stand health
Abstract: This experiment evaluated the influence of manure, peat, and vermiculite
incorporated at low and high rates (0.0118 and 0.0236 m3/m2) and under two soil moisture
regimes on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling (1+0 for 1+1) xylem
water potential ( Phi xylem), whole-plant growth, root architectural development, and subsequent
field performance under fertilized and non-fertilized conditions. Trends in soil moisture retention
were observed (high manure > high peat > control) but there were no differences in Phi xylem.
Root length in the wetter soil moisture experiment was initially (three months) greatest for
seedlings in high vermiculite and least in high manure but there were no differences among
treatments at lifting (eight months). Mean height was greatest for seedlings grown in vermiculite
and peat (wetter nursery experiment) after two field seasons. Field fertilization (35 g/seedling)
with controlled-release fertilizer in the planting hole stimulated height growth initially, but
decreased height and diameter growth during the second growing season. Dramatic improvements
associated with the use of nursery soil amendments were not realized, but the failure to identify
negative effects, a potential reduction in disease incidence, and improvement of nursery soil
physical and chemical properties may justify their use.