Plant Growth and Cutting Production of Container-grown Pelargonium Stock Plants as Affected by N Concentration and N Form

: NH4 + : ratios, N recovery, leachate Abstract. Stock plants of Pelargonium zonale 'Empress' were grown for 130 days on coarse tuff medium in a green- house. Four N concentrations (50, 100,200, and 400 mg N/liter) and three NO 3 - : 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 NH 4 + 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 quality of Pelargonium stock plants affects the size or number of cuttings and their root regeneration. Nutrition is one of the factors that has been reported to affect stock plant de- velopment and the production of cuttings (Read, 1987). Nitrogen concentrations affect plant growth and cutting yield (Lemaire, 1983; Lemaire and Dartigues, 1984; Reuther and Rober, 1980). The proportion of NO 3 - or NH 4 +