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Laura Pickett Pottorff and Karen L. Panter

With the cooperation of six commercial greenhouses (five in Colorado, one out of state), rooted poinsettia cuttings and bedding plant plugs were collected and analyzed for Pythium and Rhizoctonia, two common root rotting pathogens in Colorado greenhouses. Samples of plant, soil, and water debris were taken from four greenhouses, as well as samples of growing media ready for use. These were also analyzed for Pythium and Rhizoctonia. Fungi recovered from the plant, debris, or growing media samples were identified, grown in pure culture, and introduced into susceptible plants (Vinca minor) in pathogenicity studies. Neither pathogen was isolated from the rooted poinsettia cuttings tested. Pythium was not found in any of the plug material or in growing media. Rhizoctonia solani was found in 16% of the plug samples and 7% of the growing media samples tested. Debris from greenhouse floors yielded four species of Pythium as well as Rhizoctonia solani. Isolates of each fungus were able to colonize, but not adversely affect, inoculated plants in pathogenicity studies. It appears that disease causing organisms that have potential to decrease plant quality and growth are already present in the greenhouse. Control of root rotting pathogens can best be carried out by relying heavily on sanitation measures.

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George E. Fitzpatrick and Stephen D. Verkade

Three compost products made from urban waste materials, municipal solid waste (MSW), yard trash (YT), and a co-compost made from 1 part sewage sludge and 3 parts yard trash (S-YT), were used as growing media for production of dwarf oleander (Nerium oleander L.) in 25 cm. diameter containers. In one test the composts were used as stand-alone growing media and in a second test they were blended with pine bark (PB) and sand (S) in 2 ratios: 4 compost: 5 PB: 1 S and 1 compost: 1 PB: 1 S. The S-YT co-compost produced plants with the highest biomass in both tests. Reduced growth of dwarf oleander in each test was associated with the degree to which the media compacted during the 5.5 month production period. The MSW compost compacted an average 8.5 cm. per container when used as a stand-alone medium, while the S-YT mixes compacted much less, typically < 4.0 cm.

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J.W. Buxton and T. Phillips

In class demonstrations, it is almost impossible to maintain the same water: air ratio in growing media. If some treatments result in greater plant growth than others, treatment effects on plant growth are often confounded with the effect of water: air ratio in the growing media. In a laboratory demonstration of nutrient deficiencies symptoms in plants, a controlled water table irrigation system maintained a constant water: air ratio in the growing media regardless of the nutrient deficiency affect on plant growth. The modified capillary mat irrigation system consists of one mat edge extending over the edge of the bench into a narrow trough on the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn upward by capillarity to the bench surface and then moves by capillarity over the bench. The system automatically maintains a constant air: water ratio in the growing media. A standard Hogland solution was modified to demonstrate deficiencies in N, P, K, Mg, Ca, Cu, Fe, and Zn on corn, squash, radish, soybeans, and marigold. Seeds were germinated and grown to maturity in either a 10- or 15-cm pot. Students set up the demonstration, were provided instruction in preparing solutions, regularly observed plant growth, and answered questions at the end of the study about differences in plant growth observed. However, possibly because low concentrations of some minor elements in the capillary mat, Zn deficiency was not observed and other elements, although resulting in poor growth compared to the control, did not show severe deficiency symptoms.

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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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J.W. Buxton and Wenwei Jia

The controlled water-table irrigation (CWT) system was evaluated for vegetable seed germination and transplant growth. The system is a modification of capillary mat irrigation except that the mat along one side extends over the edge of the bench into a narrow trough running along the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn by capillarity from the trough upward to the bench surface and then moves by capillarity to the opposite side of the bench. The system automatically maintains a constant air: water ratio in the growing media. Seeds of broccoli, tomato, and pepper were germinated in a 96-cell plug tray and grown to transplanting stage with the CWT system. A factorial experiment consisted of two growing media combined with CWT treatments of 2 and 4 cm. Excellent germination and high-quality seedlings were produced with all treatments. No differences were observed in growth of seedlings at 2 vs. 4 cm or between the two growing media. The CWT system is capable of maintaining a constant uniform water: air ratio in all plug cells on a commercial growing bench. Nutrient solution does not run off the bench. The CWT potentially is an excellent system for the irrigation of vegetable transplants.

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Michael Compton and Timothy Zauche

Anaerobic digestion-derived biosolids (ADB) has the potential to become a complete or partial substitute for sphagnum peat in the greenhouse and nursery industry. Bedding plant production being one of the largest segments of the floriculture industry may possess the greatest application for this new organic addendum to soilless media. An experiment was conducted in which geraniums (Pelargonium ×hortorum `Red Elite') were grown in potting mixes formulated with vermiculite and perlite plus various concentrations and combination of anaerobic digestion-derived biosolids (ADB) and sphagnum peat to determine if ADB could be used as a partial or complete replacement for sphagnum peat in soilless horticultural growing media. Plants were grown during June and July 2003–05 in the greenhouse at 75 ± 5 °F and normal light and photoperiod. Plant growth was assessed by measuring the dry weight of stem tissue. Plants were harvested when at least 50% of the total number of plants produced at least one inflorescence. Floriferousness was measured by counting the number of visible inflorescences per plant. Dry weight of plants grown in media containing ADB was greater than those grown in media containing sphagnum peat as the sole organic addendum. Plants grown in media containing ADB were also more floriferous. This study demonstrates that ADB has great potential for use as an organic addendum to horticultural growing media as a partial or complete replacement for sphagnum peat. Use of anaerobic digester-derived biosolids in horticultural growing media is a protected intellectual property and available for license through the WiSys Technology Foundation.

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Mark T.F. Highland*, Daniel C. Sclar, Elaine R. Ingham, Karen L. Gartley, and James E. Swasey

Compost has great potential for use in horticulture; however, the relationship between compost feedstock materials and resultant compost characteristics must be well understood. Research examining plant growth response from the addition of compost to container growing media is limited. This research had two parts: the first part examined the relationship between compost feedstock materials and resultant mature compost characteristics. The second part investigated plant growth responses when compost replaced the peat component of container growing media. Two feedstock treatments were aerobically composted in turned windrows. Compost characteristics examined include pH, EC, C:N Ratio, Solvita Maturity, and several biological characteristics (total and active bacteria, total and active fungi, protozoa, spore forming bacteria, E. coli O157:H7, and total coliformic bacteria). To examine plant growth response, compost was substituted for peat (from 0%-40% by total volume) in container growing media. Crops tested were Antirrhinum majus `Rocket White', Viola × wittrockiana `Crown Azure', Oriental Hybrid Lilium `Siberia', and Chrysanthemum × grandiflorum `Yellow Kodiak'. Quantitative plant growth response measurements (shoot fresh and dry weight, percent root necrosis, flower number, and flower size) were recorded and compared by treatment. Despite initial feedstock differences between the two compost treatments, both resulted in similar compost biology and species richness. Coliformic bacteria and E. coli O157:H7 levels were below detection limits in final compost. Choice of compost feedstock materials had a significant effect on the chemical characteristics of the finished product. Compost replacement for peat resulted in plant growth greater than or equal to those of the control treatment.

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Jonathan N. Egilla

Four-week-old seedlings of Scarlet eggplant (Solanum integrifolium Poir.), a short-day fruiting vegetable, were grown for 20 weeks in a greenhouse (G/H) from 14 Mar. to 2 Aug. 2005. Mean daily photosynthetic photon flux in the G/H was about 480, 349 and 71 μmol·m–2·s–1 above-, within canopy; and at pot level, respectively in July. Seedlings were grown either in Turface® (fritted clay) or fine sand. Fertilizer treatment consisted of 5 g Osmocote® (18% N-6% P2O5-12% K2O) per pot, plus 100 mL of Peat-lite® (15% N-16% P2O5-17% K2O) solution at 200 mg·L-1 of N twice weekly, or Peat-lite only. Seedling growth (plant height, leaf number) during the first 12 weeks in both growing media was similar regardless of fertilizer treatment. The number of lateral shoots (not fruit number, FRN) increased from early fruit set (week 14) until termination (week 20), but there were no significant (P = 0.05) growing media or fertilizer treatment effects. While root dry mass was similar in both growing media, shoot dry mass was significantly (P < 0.0001) increased in fritted clay. Conversely, FRN and fruit dry mass (FDM) were, respectively, 8- and 11-fold greater in sand compared with fritted clay. Fertilizer treatment had no significant (P = 0.05) effect on both FRN and FDM either in fritted clay or sand. These trends indicate that S. integrifolium can produce limited amounts of fruit under the long daylength conditions of the summer at reduced irradiance, but factors determining shoot growth may have significant influence on fruit yield under this condition.

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Chiwon W. Lee, Jong-Myung Choi, and Chun-Ho Pak

assistance in plant tissue and growing media analyses, The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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Trisha Blessington Haley and David Wm. Reed

1 Graduate student. 2 Professor. To whom reprint requests should be sent; e-mail . We thank Oglevee LTD and Colorspot for providing plant material, Sun Gro Horticulture for providing growing media, and grant support from the