Search Results

You are looking at 1 - 4 of 4 items for :

  • Author or Editor: Ursula K. Schuch x
  • Journal of the American Society for Horticultural Science x
Clear All Modify Search

Twelve species of woody ornamentals were grown in containers in Riverside and Davis, Calif., to determine plant water use and compare crop coefficients (Kc) calculated with reference evapotranspiration (ET) from local weather stations (ETcim) or atmometers (ETatm). Water use, Kcatm, and Kccim differed by species, location, and month of the year. Raphiolepis indica (L.) Lindl., Pittosporum tobira (Thunb.) Ait., Juniperus sabina L., and Photinia ×fraseri Dress. were the highest water users in Riverside and Arctostaphylos densiflora M.S. Bak., Juniperus, Cercis occidentalis Torr., and Pittosporum used the highest amount of water in Davis, when averaged over the 20-month study period. Rhamnus californica Eschsch., Prunus ilicifolia (Nutt.) Walp., and Cercocarpus minutiflorus Abrams. were among the lowest water users in both locations. Although plant water use fluctuated considerably between individual sampling dates, the relative ranking of species water use in each location changed very little over the study period. During periods of high winds, ETcim may not provide an accurate reference for container crops. Kc values fluctuated seasonally from as much as 1 to 4.7 for high water users, while values were stable for low water users and also for Buxus microphylla japonica Rehd. & E.H. Wils., an intermediate water user. During periods of low ET, especially in fall and winter, Kc values were artificially high and failed to correspond to the plants' low water use. Kc values for low water users seem to be useful to estimate water requirements over an extended period of time, whereas general Kc values seem to have limited value for plants with high water demand and need to be modified for different growth stages and growing locations.

Free access

The objectives of this study were to determine 1) the minimum controlled-release fertilizer (CRF) rate and the lowest constant medium moisture required to produce the highest quality plants and 2) if this production system affected quality of these plants under two postproduction light levels. Two New Guinea impatiens (Impatiens sp. hybrids) `Illusion' and `Blazon' (Lasting Impressions Series) differing in salt tolerance were grown for 42 days with a CRF at three rates (3.3, 6.6, or 9.9 g/pot) and two medium moisture levels (low or high) without leaching. The high moisture level (tension setpoints of 1 to 3 kPa) and 6.6 g of CRF/pot produced optimum biomass. Low medium moisture (tension setpoints of 4 to 6 kPa) reduced leaf area, leaf number, leaf N content, root, stem, and leaf dry masses as CRF rate increased from low to high for `Illusion'. Similar results in `Blazon' were observed as CRF rates increased from 3.3 to 6.6 g. Biomass decreased no further at the high rate of 9.9 g/pot. Biomass increased in both cultivars under high medium moisture when CRF rates increased from 3.3 to 6.6 g. Biomass of `Illusion' decreased at 9.9 g/pot, although no symptoms of salt sensitivity were observed (i.e., leaf tip burn). `Blazon' maintained a similar biomass when amended with 9.9 or 6.6 g CRF/pot, although electrical conductivity (EC) in the medium was 5.9 dS·m-1 in the upper half and 4.1 dS·m-1 in the lower half of the medium at the end of production. Growth of `Illusion' responded more favorably to postproduction light levels that were similar to those of production regardless of treatment imposed during production. Similar biomass responses occurred for `Blazon' regardless of the postproduction light level.

Free access

The effects of water stress and GA, on breaking dormancy of flower buds of coffee (Coffea arabica L.) were investigated. In the first experiment, water was withheld until the trees reached leaf water potentials (WP) of -1.20, - 1.75, -2.65, or -3.50 MPa. Water potential, ethylene production, and ion leakage of flower buds and leaf disks were examined from release from water stress until anthesis. Trees that had experienced leaf WP of less than - 2.65 MPa, and flower bud WP of about - 4.0 MPa flowered within 9 days after irrigation. In flower buds where dormancy had been broken with water stress, ethylene production was low compared to dormant buds and flowers at anthesis. In the second experiment, O, 50, 100, or 200 mg GA3/liter was painted on branches of nonstressed trees. In experiment three, water was withheld until plants reached leaf WP of -0.6, -1.3, - 2.1, or - 3.0 MPa, then two branches per tree were painted with O, 50, and 100 mg GA3/liter. Gibberellic acid partially compensated for insufficient water stress to initiate flower opening. Ethylene evolution of flower buds was affected by water stress but not by GA3 treatment. Severe water stress treatments and GA, treatment (200 mg·liter-1) increased ethylene evolution of leaf disks. Ion leakage of flower buds and leaf disks was increased by severe water stress. Ion leakage of flower buds was highest at anthesis. After water stress, dormant and nondormant flower buds at the 4-mm stage could be distinguished based on their ethylene evolution. Chemical name used: gibberellic acid (GA3).

Free access

`Fontana', `Iridon', `Pink Lady', `Splendor', `White Diamond', and `White View Time' chrysanthemum (Dendranthema × grandiflorum Ramat.) were grown for 10 weeks with N rates of 80, 160, or 240 mg·L-1 constant liquid fertilization and irrigated at sufficient (high) or deficient (low) amount. Cultivars differed in growth habit, and treatments significantly affected all variables measured. Plants fertilized with 80 mg·L-1 had lower leaf and stem dry mass, less leaf area, and were deficient in leaf N compared with plants fertilized with twice the amount of N. The highest stem dry mass was produced with 160 mg·L-1. Leaf and stem dry mass were reduced 25% for plants receiving low irrigation compared to those receiving high irrigation. In general, leaf area increased when fertilizer was raised from 80 to 160 mg·L-1 but differed by cultivar and irrigation regime when fertilizer was increased to 240 mg·L-1. Three weeks after the experiment started, electrical conductivity (EC) of runoff collected weekly from `White Diamond' plants fertilized with 240 mg·L-1 exceeded the average EC of the irrigation solution. The 240 mg·L-1 treatment also resulted in excessive EC in the growing substrate at the end of the experiment and reduced stem dry mass by 11% compared with the 160 mg·L-1 fertilizer regime. Substrate EC differed between cultivars in response to fertilizer and irrigation. Significantly more adult western flower thrips [Frankliniella occidentalis (Pergrande)], 55% and 52%, were found on the foliage of `Pink Lady' and `Fontana', respectively, than on `Iridon'. `Pink Lady' and `Fontana' had more immature thrips at the end of the experiment than `Iridon' and `White View Time'. Fewer adults and immatures were found on plants fertilized with 80 mg·L-1 than 240 mg·L-1. Fewer adults were detected in plants under high versus low irrigation, while irrigation had no effect on the number of immatures. The simultaneous use of plant varietal resistance and plant cultural growing techniques has the potential to lower thrips populations on chrysanthemum.

Free access