Stock plants of Pelargonium zonale `Empress' were grown for 130 days on coarse tuff medium in a greenhouse. Four N concentrations (50, 100,200, and 400 mg N/liter) and three NO3-: NH4+: ratios (70:30, 60:40, and 40:60) were applied. The development of mother plants, production of cuttings, and the recovery of applied N were measured. Number of cuttings was not affected by any treatments except for the low N concentration. The proportion of absorbed N was higher than that of water in the plants treated with 50 or 100 mg N/liter, while those fertilized with 200 or 400 mg N/liter absorbed more water relative to N uptake. Nitrogen recovery efficiency decreased from 70% to 10% for the 50- to 400-mg N/liter treatments, respectively. Percentage of applied N lost by leaching (30% to 70%), and N that could not be accounted for (0.5% to 20%), increased with increasing N concentration and NH4+ percentage in the solution. The minimum concentration to be used in fertilization of Pelargonium mother plants is 100 mg N/liter. Optimal N supplied ranged between 100 and 200 mg N/liter.
The objectives of the present research were to study the effects of pH, NH4:NO3 ratio, and P concentration in the nutrient solution on development of Leucadendron R. Br. `Safari Sunset' [L. salignum Bergius × L. laureolum (Lam.) Fourc.]. The experiment was conducted in aero-hydroponic systems and involved six treatments in a nonfactorial design: two pH levels (5.5 and 7.5), two P levels (7 and 20 mg·L–1), and two NH4:NO3 ratios (60:40 and 25:75). The pH of the root environment was the most important factor controlling growth. Root cells were longer in plants grown at pH 5.5 than at pH 7.5, but width was not affected. Altering the NH4:NO3 ratio did not affect development regardless of pH. Increasing the P concentration from 7 to 20 mg·L–1 significantly decreased root fresh weight at the low pH and slightly reduced shoot growth. Nitrogen, P, K, Zn, and Mn concentrations were higher, while that of Fe was lower in plants grown at low pH. Reducing the NH4:NO3 ratio did not affect N concentration but increased P and K concentrations in the shoots. Increasing the P concentration significantly raised the P content of shoot and root tissues but reduced the content of Fe, Zn, and Mn.