Impatiens (Impatiens wallerana Hook. f.) is the most important annual bedding plant in the US, based on wholesale dollar volume. Production of high-quality plants requires optimization of the nutrition regimen during growth, especially the total nitrogen (N) concentration and the ratio of N sources. Our objective was to determine the N concentration and ratio of N sources that optimize bedding-plant impatiens growth and development. We used four N concentrations (3.5, 7, 10.5, and 14 mmol·L-1 of N) in factorial combination with four ratios of nitrate-N (NO3 --N) to ammonium-N (NH4 +-N) (4:0, 3:1, 1:1, and 1:3). Application of treatments began at day 30, and every-other-day applications were conducted until day 60. From day 60 to day 70 only deionized water was applied. N concentration and source displayed interation for most growth parameters. When N was supplied at a concentration ≤7 mmol·L-1, the NO3 --N to NH4 +-N ratio did not affect growth. When N was supplied at a concentration ≥10.5 mmol·L-1, a 1:3 NO3 --N to NH4 +-N ratio yielded the greatest shoot dry weight, shoot fresh weight, plant diameter, and number of flower buds per plant. With a NO3 --N to NH4 +-N ratio of 4:0, these growth parameters decreased. To produce high-quality, bedding-plant impatiens, N should be applied at NO3 --N to NH4 +-N ratios between 1:1 and 1:3 in combination with an N concentration of 10.5 mmol·L<-1 at each fertigation from day 30 to day 60 of the production cycle.
Fredy R. Romero*, Richard J. Gladon, and Henry G. Taber
James E. Faust, Veronda Holcombe, Nihal C. Rajapakse, and Desmond R. Layne
Daily light integral (DLI) describes the rate at which photosynthetically active radiation is delivered over a 24-hour period and is a useful measurement for describing the greenhouse light environment. A study was conducted to quantify the growth and flowering responses of bedding plants to DLI. Eight bedding plant species [ageratum (Ageratum houstonianum L.), begonia (Begonia ×semperflorens-cultorum L.), impatiens (Impatiens wallerana L.), marigold (Tagetes erecta L.), petunia (Petunia ×hybrida Juss.), salvia (Salvia coccinea L.), vinca (Catharanthus roseus L.), and zinnia (Zinnia elegans L.)] were grown outdoors in direct solar radiation or under one of three shade cloths (50, 70 or 90% photosynthetic photon flux (PPF) reduction) that provided DLI treatments ranging from 5 to 43 mol·m–2·d–1. The total plant dry mass increased for all species, except begonia and impatiens, as DLI increased from 5 to 43 mol·m–2·d–1. Total plant dry mass of begonia and impatiens increased as DLI increased from 5 to 19 mol·m–2·d–1. Impatiens, begonia, salvia, ageratum, petunia, vinca, zinnia, and marigold achieved 50% of their maximum flower dry mass at 7, 8, 12, 14, 19, 20, 22, and 23 mol·m–2·d–1, respectively. The highest flower number for petunia, salvia, vinca, and zinnia occurred at 43 mol·m–2·d–1. Time to flower decreased for all species, except begonia and impatiens, as DLI increased to 19 or 43 mol·m–2·d–1. There was no consistent plant height response to DLI across species, although the shoot and flower dry mass per unit height increased for all species as DLI increased from 5 to 43 mol·m–2·d–1. Guidelines for managing DLI for bedding plant production in greenhouses are discussed.
Jianjun Chen, Richard C. Beeson Jr., Thomas H. Yeager, Robert H. Stamps, and Liz A. Felter
Irrigation runoff water from a containerized landscape plant production bed was blended with rainwater from green house roofs in a constructed collection basin. Water from both the collection basin and an on-site potable well were characterized and used to grow foliage and bedding plants with overhead and ebb-and-flow irrigation systems. Over a 2-year period, a total of 18 foliage and 8 bedding plant cultivars were produced with plant growth and quality quantified. Alkalinity, electrical conductivity, hardness, and concentrations of nutrients of water from both sources were well within desired levels for greenhouse crop production. Turbidity and pH were relatively high from algal growth in the collection basin. However, substrate pH, irrigated by either water source, remained between 6 and 7 throughout the production periods. All plants at the time of finishing were of marketable sizes and salable quality independent of water source. No disease incidences or growth disorders related to water sources were observed. Results suggest that captured irrigation runoff blended with rainwater can be an alternative water source for green house crop production.
Dharmalingam S. Pitchay*, Jonathan M. Frantz, and James C. Locke
Currently, formulation of inorganic fertilizers is based on cation amounts such as NH4, K, Mg, Ca, Fe, MN Cu, and Zn, whereas anion species and amounts are viewed, with few exceptions, as necessary fillers. The delivery of cations in the nutrient solution is associated with an anion such as Cl, SO4, NO3, PO4 or CO3. These anions at higher concentrations can result in different growth responses by altering the rhizosphere pH, soluble salts, and influencing the uptake of both cations and anions. The impact of these anions has not been extensively studied in the formulation of inorganic fertilizers. Several experiments assessed the effect of SO4 and Cl on root and shoot growth and development of bedding plants represented by petunia, impatiens, and vinca. In all treatments, plant height, shoot and root dry weight, and flower number decreased with an increase in Cl concentration. Root morphology was marked by fewer total roots and shorter primary and secondary roots when grown with Cl anions compared to the plants grown with SO4 anions. This indicates that anions have a larger role in determining optimum fertilizer formulation than previously believed. This information provides an additional tool in formulating fertilizers for greenhouse bedding plant production.
John A. Biernbaum, William Argo, and Janet Pumford
161 WORKSHOP 27 Use of Plant Sap Tests for Determining Nutrient Status of Horticultural Crops
Marc W. van Iersel
Bedding plants are exposed to a wide range of environmental conditions, both during production and in the landscape. This research compared the effect of short-term temperature changes on the CO2 exchange rates of four popular bedding plants species. Net photosynthesis (Pnet) and dark respiration (Rdark) of geranium (Pelargonium ×hortorum L.H. Bail.), marigold (Tagetes patula L.), pansy (Viola ×wittrockiana Gams.), and petunia (Petunia ×hybrida Hort. Vilm.-Andr.) were measured at temperatures ranging from 8 to 38 °C (for Pnet) and 6 to 36 °C (for Rdark). Net photosynthesis of all species was maximal at 14 to 15 °C, while Rdark of all four species increased exponentially with increasing temperature. Gross photosynthesis (Pgross) was estimated as the sum of Pnet and Rdark, and was greater for petunia than for the other three species. Gross photosynthesis was less sensitive to temperature than either Pnet or Rdark, suggesting that temperature effects on Pnet were caused mainly by increased respiration at higher temperatures. Gas exchange-temperature response curves were not useful in determining the heat tolerance of these species. There were significant differences among species in the estimated Rdark at 0 °C and the Q10 for Rdark. Differences in the Q10 for Rdark were related to growth rate and plant size. Large plants had a greater Q10 for Rdark, apparently because these plants had a higher ratio of maintenance to growth respiration than small plants. The Q10 of the maintenance respiration coefficient was estimated from the correlation between the Q10 and relative growth rate, and was found to be 2.5 to 2.6.
Clydette M. Alsup and Pamela A. Trewatha
The rocky Ozarks soils make it difficult for some homeowners to establish ornamental gardens. An alternative to digging in rocky soils is planting into bags of potting soil. This study evaluated “Gardening in a Bag” for herbaceous bedding plants. The growth and appearance of Alternanthera, Capisum annuum, Dianthus, Gazania, Tagetes `Wave', and upright petunias, Salvia splendens, Spilanthes, Verbena, and Catharanthus roseus were evaluated in 2002 under two planting methods: in the ground vs. in bags of potting soil. Wave petunias, Dianthus, C. roseus, and Portulacagrandiflora were evaluated in 2003. All plants were mulched with 3 inches of coarse sawdust. In 2002, planting method had no effect on average height for 16 of the 25 cultivars tested. Seven cultivars were taller when grown in the ground while two cultivars were shorter in that treatment. Planting method had no effect on average plant width of 13 of the cultivars. Plant width was greater for nine cultivars grown in bags, while three cultivars were wider when grown in the ground. Visual ratings were similar for 14 of the cultivars, regardless of planting method. In 2003, performance of five species was evaluated on 3 and 29 July and 5 Sept. Plant height and width were greater on plants grown in the ground than plants grown in bags on 3 July and 5 Sept. Only plant width was significantly greater in the soil-grown plants on 29 July, although the greater height trend was still evident. Plants in the ground had more flowers than plants in bags on 3 July, but there were no differences in flower number the other two dates. Visual quality ratings were taken on the second and third dates, with no differences between treatments. Root soil temperature was higher in bags than in the ground on all three dates in 2003.
J. M. Gehring and A. J. Lewis III
Hydrogel incorporated in the growing media of 2 bedding plants, marigold ‘Dolly’ (Tagetes erecta L.) and zinnia ‘Pink Buttons’ (Zinnia elegans Jacq.) grown in 3 different size containers generally increased hours to wilting (HTW) sequentially in both species and with increasing rates of hydrogel over the range tested (4 to 16 kg/m3). HTW of marigold and zinnia grown in 5.1 cm3 containers in hydrogel amended media at 16 kg/m3 increased 45 and 37%, respectively. High rates of hydrogel incorporation were as effective in increasing HTW in small containers as was doubling container size. Pressure bomb studies with plants grown under stress in hydrogel-amended media confirmed the reduction in internal moisture tension.
M.E. Shedlosky and J.W. White
Nine bedding plant vegetable and flower cultivars were grown in each of 10 night air and root media temperature regimes. Generally, fresh and dry weights were greater at 16°C than at 7° night air temperature when root-zone (RZ) heating was not used. Soil warming increased fresh and dry weights of all cultivars grown at 16° night air temperatures. When air temperatures were below 16°, soil warming maintained fresh and dry weights equivalent to or better than plants grown at 16° without soil warming. Two split-night (SN) air temperature regimes were as effective as a constant 16° night temperature, ranking first and 3rd in fresh and dry weight per unit of energy consumption. All soil warming treatments had higher energy productivity than the 16° air temperature treatment with no RZ heating.
This experiment was conducted to determine the effects of bed type (single or parallel raised bed vs. nonbedded); plant density (1991: ≈148,300 or 269,500 plants/ha; 1993: ≈148,300, 269,500, or 432,400 plants/ha); and use of black or white degradable mulch vs. nontreated soil on total and marketable yields and number of marketable seed per kilogram (seed count) of `Fleetwood', an erect bush, white-seeded navy bean (Phaseolus vulgaris L.). Spray-on mulch degraded before canopy closure, but a residue was present at harvest. In 1991, treatments did not affect yield or seed count. In 1993, bedding did not affect yield over nonbedded seedbeds. Black spray-on mulch increased marketable yield over plants grown with white spray-on mulch. Total and marketable yields were significantly higher at 269,500 than at 148,300 plants/ha. Bed type and plant density did not affect seed count, but seed count increased with black spray-on mulch. Dry beans should not be grown on beds under soil conditions such as those in our experiment. White spray-on mulch had no beneficial effect, but using black mulch needs additional evaluation. Planting at 269,500 plants/ha likely will yield ≈2 Mg seeds/ha in most years.