Fig. 1. Response of pawpaw (Asimina triloba) seedlings to Osmocote 14–14–14 (14N–6.1P–11.6K) slow-release fertilizer incorporated in the potting substrate at different rates for seedling leaf number (A) and seedling height (B) 10 to 17 weeks after sowing. Letters correspond to treatment means that were significantly different by least significant difference (P < 0.05) at each date; 1 kg·m-3 = 2.2 lb/yard3, 1 cm = 0.39 inches.
control and medium Osmocote treatment rate, with the greatest root dry weight occurring at 500 mg·L-1 Peters (see columns in Table 3). Root dry weight within each level of Peters showed a quadratic response to increasing rate of Osmocote, with the greatest root dry weight at the me-
dium and high treatment rates of Osmocote (see rows in Table 3). Shoot dry weight showed a linear response to increasing rate of Peters at all rates of Osmocote, with the greatest shoot dry weight at the highest rate of Peters. Shoot dry weight within each level of Peters showed a quadratic response to increasing treatment rates of Osmocote, with the greatest shoot dry weight at both the highest treatment rates of Osmocote and Peters. Total plant dry weight showed a linear response to increasing rate of Peters in the control, medium, and high treatment rates of Osmocote. Total plant dry weight showed a quadratic response to increasing rates of Peters at the low treatment rate of Osmocote. Total plant dry weight within each
level of Peters showed a linear response to increasing rates of Osmocote, with the greatest total plant dry weight at the highest treatment rates of Osmocote and Peters. Root to shoot ratio showed a quadratic response in the Osmocote control, and a linear response at the low, medium, and high treatment rates of Osmocote, to increasing rates of Peters. Root to shoot ratio within each level of Peters showed a linear response to increasing treatment rate of Osmocote without Peters application, with the lowest root to shoot ratio at the high treatment rate of Osmocote. Root to shoot ratio in either the 250 or 500 mg·L-1 Peters treatment levels showed a quadratic response to increasing rate of Osmocote, with the lowest root to shoot ratio (0.67) at the highest treatment rates of both Peters and Osmocote.
EXPERIMENT 2. SLOW-RELEASE FERTILIZER APPLICATION ONLY. No significant treatment differences were observed for seed germination percentage (average germination percentage was 70%; data not shown). Note that treatment A for Osmocote in this experiment is the same rate as the high rate of 0.81 kg·m-3 used in the slow-release and weekly liquid-feed fertilizer application experiment described previously. Seedling emergence and growth, based on leaf number at 10 weeks after sowing, were hastened in treatment B and delayed in treatment E (Fig. 1A). Thirteen weeks after sowing, seedling leaf number in all other treatments was similar to that in treatment B, except for seedlings in treatment E which had two to three leaves where seedling in all other treatments had four to five leaves. When seedlings were harvested 17 weeks after sowing, plants in treatment D had the highest leaf number and control plants had the lowest number. Seedlings in treatment E had accelerated growth over the last 3 weeks of culture, finishing with a similar number of leaves to those in treatments C and D.
Seedling height, 10 weeks after sowing, was about 4 cm (1.6 inches) in treatment E; seedlings had already reached a height of about 8 cm (3.1 inches) in treatment B and about 6.5 cm (2.6 inches) in all other treatments by this time (Fig. 1B). Thirteen weeks after beginning measurements, seedling heights obtained with treatment E were lowest, whereas heights for