Application . Best growth and nutrient status of container seedlings was attained with an irrigation cycle where substrate moisture regime was maintained close (8%) to container capacity. Moisture stress reduced plant nutrient uptake, although tissue nutrient concentrations were unaffected . Container capacity was a sensitive indicator of the irrigation requirements of seedlings .Abstract. Containerized red pine (Pinus resinosa Ait .) seedlings were grown over a 16-week rotation at different irrigation treatments to assess moisture stress on plant growth and nutrition, and to evaluate container capacity as a guide for irrigation . Wet, moist and dry moisture regimes were induced by watering trees to the container capacity weight of the growing medium after declining to respective 92, 73 and 57% of this reference weight . The seedlings received the same amount of fertilizer over the growth period . Maximum shoot and root growth was attained under the wet moisture regime, but biomass was reduced 21 and 43% for the moist and dry regimes. Plant nutrient concentrations were not significantly affected by watering treatment, and vector diagnosis of dry matter production and element composition indicated that macronutrients were non-limiting . Seedling nutrient uptake however, was significantly diminished by moisture stress which was attributed to decreased root growth and lower mass flow and diffusion of nutrients when moisture availability was reduced in the peat rooting media . Container capacity was found to be a sensitive reference for judging the watering requirements of greenhouse-grown containerized seedlings . The method can be relatively easily applied on an operational basis .

Containerized red pine (Pinusresinosa Ait.) seedlings were reared on different fertility regimes that compared conventional applications of a recommended 39 mg N per seedling as a complete nutrient solution (175 mg N•L−1) with more frequent applications of an equal, one-half, or one-quarter amount of nutrients delivered at exponentially increasing solution concentrations over the same time period. Height growth, dry matter production, and root development at the end of the greenhouse rotation was significantly greater for seedlings receiving nutrients at exponentially rather than constantly increasing rates, although shoot growth among the three exponential treatments did not differ significantly. The increased yield was attributed to improved seedling nutrition as fertilizer addition rates better matched exponential growth development and nutrient consumption of the plants. The results indicate that superior seedlings can be grown successfully at low concentrations of nutrient solution, applying only one-quarter of the fertilizer dose conventionally used for container stock production.

Conventional fertilization of black spruce (Piceamariana (Mill.) B.S.P.) container stock usually does not conform to steady-state nutrient conditions and may limit subsequent outplanting performance. Steady-state nutrient preconditioning of seedlings, characterized by maintaining stable tissue nutrient (N, P, and K) concentrations during the exponential growth phase, was induced by an exponentially based fertilization regime that compensated for low nutrient reserves in germinating seeds. By the end of the greenhouse rotation, this regime reduced the shoot/root ratio of the trees, but fell short of increasing seedling growth and nutrient status when compared with seedlings conventionally fertilized with equivalent amounts of nutrients. However, first-season height growth and shoot biomass of trees outplanted on different surface soils in pot bioassays were significantly improved by steady-state nutrient preconditioning and were accompanied by increased plant nutrient uptake, particularly N at the half-dose level and P at the full-dose level. Out-planting performance was higher on an upland site type, although relative response was greater on nutrient-poorer, lowland substrates. The preconditioning response from exponentially based fertilization was attributed to lower shoot/root mass ratio and more effective nutritional adaptation of the seedlings to the field environment. Under steady-state nutrient culture, seedling nutrient uptake conforms more closely with stable nutrient supply in nature, since expanding root systems exploit new soil volumes exponentially. Field performance of exponentially fertilized seedlings may be further enhanced when combined with balanced nutrient loading in the greenhouse phase.

Containerized red pine (Pinus resinosa Ait.) seedlings were fertilized to test the effectiveness of three approaches (critical levels, optimal ratios, and vector analysis) to diagnose seedling nutrient status. Treatments involved a balanced nutrient solution and six imbalanced solutions lacking (−) or enriched (+) with N, P, or K applied to seedlings raised in peat‐filled paperpots. Growth was significantly reduced by ‐N, ‐P, and +N treatments indicating N and P deficiencies and N toxicity, respectively, and probable sufficiency or luxury consumption of P or K for the other treatments. Diagnosis by vector analysis agreed closely with actual growth and nutritional responses to treatments, and was more precise than the other approaches. Vector analysis was independent of predetermined standards or critical values, and improved identification of dilution effects and nutrient interactions which tend to complicate conventional diagnostic techniques.

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