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Jianjun Chen, Yingfeng Huang, Zhen Yang, Russell D. Caldwell, and Cynthia A. Robinson

Containerized ornamental plant production represents extremely intensive agricultural production. An average of 200,000 containers may occupy 1 acre of surface area, to which a large amount of chemical fertilizers will be applied. Because of the use of high-drainage soilless potting mixes coupled with excessive fertigation, a great amount of nutrients, particularly nitrogen and phosphorus, are leached, which increases the potential for ground and surface water contamination. Over the past 2 decades, research has been centered on developing fertigation delivery systems such as nutrient film techniques, ebb-and-flow and capillary mat systems, for reducing leaching. Relatively limited research has been conducted on improving potting medium substrates to minimize nutrient leaching. The objectives of this study were to determine the adsorption isotherm of six different zeolites to ammonium, nitrate and phosphorus, identify and incorporate desired zeolites in a peat/bark-based medium for reducing nutrient leaching in ornamental plant production. Results indicated that the zeolites possess great holding capacities for ammonium, nitrate, and phosphorus. Compared to control, ammonium leaching was reduced 70% to 90%, phosphorus 30% to 80% and nitrate 0% to 60% depending on zeolite species and quantity used per pot. Zeolite amended media caused no adverse effects on plant growth. Conversely, biomass increased significantly when compared to that of the control.

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Timothy K. Broschat

Spathiphyllum Schott. 'Mauna Loa Supreme' grown for 6 months in a fine sand soil or a 5 pine bark: 4 sedge peat: 1 sand medium (by volume) were fertilized with 7.6g N, 1.4g P, and 4.5g K/3.5-liter container by 4 different methods. The same raw fertilizer prills (21N-3P-12K) were applied weekly as a liquid, monthly as soluble granules, bimonthly as a lightly resin-coated fertilizer (Osmocote), or every 6 months as a heavily resin-coated fertilizer. All leachates were collected and were measured and analyzed weekly for N O3, PO4, and K. Spathiphyllum grew best in the sand soil with either of the controlled release formula- tions, but fertilization method had no effect on growth in the potting medium. Nitrate and K leaching losses from the potting medium were lowest from the controlled release fertilizers and highest from the soluble granules. Liquid fertilization resulted in the highest amounts of PO4 lost to leaching and controlled release fertilizers the least. In the fine sand soil, NO3 leaching was equivalent from all methods. Soluble granules had the highest levels of leached K and PO4 and the lightly-coated fertilizer lost the least due to leaching.

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David Wees

`Caruso' tomatoes were grown in a glass greenhouse in Winter and early Spring 1991. All plants were grown in 16-liter nursery pots. Half the plants were grown in a conventional peat-lite medium (Profi-mix) and were fertilized with synthetic water-soluble fertilizer containing micronutrients and (in ppm) 187 N, 46 P, 278 K, 177 Ca, and 48 Mg. The other plants were grown in a potting medium composed of 1 mature compost (chicken manure and leaves): 1 loam: 2 vermiculite (by volume); this medium was amended with 1.5 kg bone meal (2N–10P–0K) and 3 kg dolomitic lime/m3. The “organic” treatment was fertilized with a fish emulsion solution containing (in ppm) 150 N, 13 P, and 25 K. The experiment was repeated in 1992 with `Capello'. In both years, fruit were harvested around the half-ripe to three-quarters ripe stage. All insect control was with insecticidal soap and bio-control agents. A blind taste test was conducted on campus in both years. In 1991, of 70 participants, 73% preferred the “conventional” tomatoes, 20% preferred the organic tomatoes, and 7% expressed no preference. In 1992, of 105 participants, 67% preferred the “conventional” tomatoes, 24% preferred the organic tomatoes, and 10% expressed no preference.

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Mary Ann Rose and Hao Wang

Micronutrient supplements were applied to container rhododendron (Rhododendron L. × `Girards Scarlet' [Girard Evergreen Hybrid Group]) in three forms: uncoated micronutrient fertilizer; slow-release, NPK-plus-minors fertilizer; and biosolids compost (15% v/v). Control plants received no supplement. While all micronutrient treatments had significantly higher foliar Mn or Cu concentrations than controls 1 year after potting, they did not increase growth (dry weight) or plant quality. At 1, 3, and 12 months after potting, the compost treatment had significantly higher diethylenetriaminepentaacetic acid (DTPA)-extractable levels of Mn, Fe, and Zn in the medium. Only one micronutrient fertilizer treatment increased extractable micronutrient concentrations (Cu) on all testing dates. Correlations between medium-extractable and foliar micronutrient concentrations were low (r 2 < 0.30). Vigorous growth in the control treatment suggested that adequate levels of micronutrients were supplied by the pine bark-hardwood bark-peat-sand medium. September concentrations [ppm (mg·L-1)] as low as 2.0 Mn, 17.8 Fe, 0.3 Cu, 4.2 Zn, and 0.9 B in DTPA extracts produced acceptable growth in rhododendron through the following June.

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Marc W. van Iersel and Krishna S. Nemali

We examined the effectiveness of an elevated capillary mat system to maintain constant and different moisture levels in the growing medium and verify the potential of drought stress conditioning in producing small and compact bedding plants. To differentiate between plant height and compactness, we determined compactness as the leaf area or dry mass per unit stem length. Marigold `Queen Sophia' (Tagetes erecta L.) seedlings were grown in square, 9-cm-wide, 10-cm-high containers filled with a soilless growing medium. A capillary mat was laid on top of a greenhouse bench which was raised by 15 cm on one side compared to the other side to create an elevation effect. Seedlings were subirrigated by immersing the low end of the capillary mat in a reservoir of water. The amount of water moving to the higher end of the mat progressively decreased with elevation. The moisture content in the growing medium averaged from 26 to 294 mL/pot at different elevations. Regression analysis indicated that growth parameters including, shoot dry mass, leaf area, leaf number, and plant height decreased linearly with decreasing soil moisture content in the growing medium. Of all the measured growth parameters, plant height was found to be least sensitive to decreasing moisture content in the growing medium. Plants in high moisture treatments had more dry mass and leaf area per unit length of the stem compared to those in low moisture treatments. Our results indicate that drought stress can produce small, but not truly compact bedding plants.

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Mark H. Brand

Nursery production of many ornamental grasses involves potting of established liners into 8.5-L containers. Direct potting of bare root divisions into 8.5-L containers may represent a more efficient production method. Large and small divisions (based on number of tillers and volume) of eight ornamental grasses were potted directly into 8.5-L containers. The potting medium used was a 3 aged pine bark: 2 peat moss: 1 sand nursery mix (by volume), amended with dolomitic lime at 3 kg/yard3, and top dressed with Sierra 17-6-10 plus minors at 40 g/container, 8 to 9 month fertilizer. Plants were grown outdoors in a container nursery from May through September. All grasses tested performed well using the direct potting method, with 100% survival. Large divisions of Miscanthus sinensis cultivars produced plants with greater fresh weight, dry weight and number of tillers than did small divisions. Division size did not affect Miscanthus foliage or flower height but did affect number of flowers for `Graziella' and `Purpurascens'. Large divisions of Calamagrostis `Karl Foerster', a grass grown primarily for flowering, produced twice as many flowers as small divisions. Panicum virgatum and Pennisetum alopecuriodes showed signs of nutrient stress when grown from large divisions. Although a greater number of tillers was produced by large divisions of Panicum and Pennisetum, fresh weight, dry weight, flower height, and foliage height were similar to or less than that observed on plants from small divisions.

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Sauveur Mahotiere and Clarence Johnson Jr.

Mary Washington, UC157F1, and UC157F2 asparagus cultivars were grown from 1-year-old crown under greenhouse conditions in 30-liter pots containing Pro-Mix medium. The roots were cut to 10 cm prior to planting on 12 Feb. 1991. On July 12, 1991 the plants were transferred outdoors and sprayed with BA, GA4/7 and Promalin at 400 mg. liter-1 using tap water as control. On July 16, 1991 the treated ferns were cut at ground level and the plants were returned to the greenhouse, and arranged in a RCB design. Seven reps with one pot/rep were used. Data on time of emergence of first shoots were recorded daily until all pots had produced at least 1 shoot. When all plants had sprouted, cumulative number of all shoots/pots was recorded weekly thereafter over 5 weeks. BA and Promalin reduced time of emergence of shoots and increased the number of shoots/plant. GA4/7 had no effect on shoot emergence or shoot number.

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Guillermo Cardoso, Roger Kjelgren, Teresa Cerny-Koenig, and Rich Koenig

Low water landscapes are increasing popular and important in the urban areas of the Intermountain West (IMW). Perennial wildflowers are an essential part of low water landscapes, and are a dominant plant type in IMW native habitats. We compared pot-in-pot (PIP) vs. conventional above-ground (CAG) production of six IMW native wildflower species, Mirabilismultiflora, Aquilegia caerulea, Penstemon palmeri, Polemonium foliosissimum, Sphaeralcea grossularifolia, and Penstemonstrictus in #1 (4-L) containers. Media temperature, container-plant water loss, stomatal conductance, and growth were measured during two production cycles per year over 2 years. Growing medium temperatures in the PIP system averaged 10 °C cooler than in the CAG system. Consistent with cooler growing media, overall water loss of PIP-grown plants averaged 10% lower than plants grown in the CAG production system. Lower growing media temperatures apparently affected transpiration, as stomatal conductance was about 60% higher in the PIP system as compared to the CAG-grown plants. The integrated effect of lower growing media temperatures on plant performance resulted in about one-third greater top and root growth for plants growing in the PIP system compared to those in the CAG system. Pot-in-pot production may be an economically suitable nursery system for producing IMW native perennial wildflowers by reducing water loss and enhancing growth.

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Junne-Jih Chen, Ming-Chung Liu, and Yang-Hsiu Ho

Tuber production of calla lily (Zantedeschia elliottiana Spreng cv. Super Gold) was investigated using three size ranges (7-10, 4-7, and <4 mm shoot diameter) of in vitro plantlets acclimated in either pots or soil beds in a protected house. The shoots and tubers of large plantlets exhibited higher rates of dry-matter accumulation than did those of small plantlets. The diameter of tubers harvested from pots ranged from 0.67 to 4.1 cm with median values of 2.7, 2.1, and 1.9 cm for the plants derived from large, medium, and small plantlets, respectively. Plants grown in soil beds, regardless of size, produced larger tubers than did those grown in pots. Tubers >3 cm in diameter developed on 25% and 52% of plants grown in pots and soil beds, respectively. Our results suggest that improved calla lily production could be realized by using larger in vitro plantlets as the source material and growing them in soil beds in a protected house.

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Anne K. Carter

In the northeastern United States, vegetable crop classes and growers' meetings are often held during winter months when field demonstrations are impossible. A pot-sized demonstration was set up in the greenhouse in May and Nov. 2002 as a student laboratory to show the effects of season extension materials on the early growth of winter squash. The treatments were black plastic mulch and rowcover, alone and in combination. The treatments were also placed on either a heated [18.3 °C (65 °F)] or unheated germination mat to simulate warmer and cooler spring soils. Butternut squash (Cucurbita moschata) was sown in 10.2 × 10.2 × 11.43-cm (4 × 4 × 4.5 inches) pots in soilless medium. The plants were grown and observed for 30 days, then harvested and weighed. The plants in the greenhouse grew as expected of plants grown under similar conditions in the field. Bottom heat, mulch, and rowcover had an increasingly greater effect on the growth of subsequent leaves as shown by comparisons of leaves 1, 2, and 3. Warmer soils tended to have the greatest effect on all measured parameters, but this was not as obvious in the May experiment as it was in the November experiment. Thus, this pot demonstration can be used in a student laboratory. The pots and plants are small enough to transport to and set up at winter growers' meetings as well.