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Helen T. Kraus and Stuart L. Warren

An experiment was conducted to develop a protocol for using compost in nursery crop production. Five rates of inorganic fertilizer (0, 1, 2, 3, and 4 g N) and two irrigation volumes (600 and 900 mL per 3.8-L container) were evaluated for their effects on Rudbeckia fulgida Ait. `Goldsturm' and Cotoneaster dammeri Schneid. `Skogholm' growth in a pine bark substrate amended with composted turkey litter (CTL). Additions of ≥2 g N per container for cotoneaster and ≥1.0 g N for rudbeckia were required to produce growth equivalent to that of plants in a control treatment that simulated typical production by a grower in the southeastern United States. Phosphorus, Ca, and Mg contents of cotoneaster and rudbeckia plants grown in CTL-amended substrates with no fertilizer added (0 g N) were similar to or greater than that of the control. Phosphorus concentrations in the substrate solutions were higher in all CTL-amended substrates than in the control regardless of fertilizer addition. This suggests that P released from CTL had a greater impact than P added with fertilizer. The greatest nutrient value of CTL may be as a P source and a replacement for dolomitic limestone and micronutrients in container-grown plant production.

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Helen T. Kraus and Stuart L. Warren

Five ratios of NH4:NO3 (100:0, 75:25, 50:50, 25:75, and 0:100) were evaluated for impacts on growth of Cotoneaster dammeri Schneid. `Skogholm' (cotoneaster) and Rudbeckia fulgida Ait. `Goldsturm' (rudbeckia). Nitrate decreased dry weight and leaf area, while nutrient solutions containing >25% NH4 increased shoot and root growth of cotoneaster and rudbeckia. Additionally, NO3 decreased accumulation of some cationic nutrients and N in roots and shoots of cotoneaster and rudbeckia compared to solutions containing either NH4 alone or mixes of NH4 and NO3. Nitrogen contents (in milligrams) in cotoneaster fertilized with NO3 decreased an average of 54% and 58% in rudbeckia compared to N supplied as NH4 alone. These dramatic reductions in growth and tissue nutrient content reiterate the need for proper N form selection. Root diameter of cotoneaster was higher with a mix of NH4 and NO3 than with NO3 alone; whereas, the N form had no impact on diameter of rudbeckia roots. However, the stele of both cotoneaster and rudbeckia roots was larger and contained more secondary xylem with larger tracheary elements with a mix of NH4 and NO3 compared to nutrient solutions with NO3 alone. Increased number and size of secondary tracheary elements may relate to increased dry weight and leaf area of both cotoneaster and rudbeckia fertilized with mixes of NH4 and NO3 compared to NO3 alone.

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Helen T. Kraus, Stuart L. Warren, and Charles E. Anderson

Five ratios of NH4+: NO3-(100:0, 75:25, 50:50, 25:75, and 0:100) were evaluated for impact on growth of Cotoneaster dammeri Schneid. `Skogholm' (cotoneaster), a woody ornamental shrub, and Rudbeckia fulgida Ait. `Goldsturm' (rudbeckia), an herbaceous perennial. Nitrate alone decreased dry weight and leaf area of cotoneaster and rudbeckia compared with mixtures of NH4+ and NO3- and NH4+ alone. Additionally, NO3- alone suppressed accumulation of cationic nutrients and N in cotoneaster, while mixes of NH4+ and NO3- enhanced accumulation of nutrients in roots and shoots of rudbeckia compared with solutions containing either NH4+ or NO3- alone. The steles of roots of cotoneaster and rudbeckia contained more secondary xylem with larger tracheary elements with a mix of 25 NH4+: 75 NO3- than with NO3- alone.

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Helen T. Kraus, Robert L. Mikkelsen, and Stuart L. Warren

Traditional N mineralization studies have been conducted by soil scientists using soils and temperatures found in field production. As temperature, in part, governs the rate of mineralization, and container substrates reach much higher temperatures than do soils, the effect of these elevated temperatures on mineralization must be considered to begin to understand N mineralization in container substrates during production. The N mineralization patterns of three composts [turkey (Meleagris gallopavo) litter, yard waste, and municipal waste] were determined under three temperature regimes (45, 25, and 45/25 °C). More organic N was mineralized from composted turkey litter (CTL) than from municipal or yard composts, regardless of temperature. The percentage of organic N mineralized from CTL was greater at 45/25 and 45 °C than at 25 °C.

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Paige L. Herring, Abbey C. Noah, and Helen T. Kraus

Sphagnum peat is a finite resource that is often used in the horticultural industry as a component in many substrates, especially for greenhouse production of transplants. Because peatlands are being depleted by vast amounts of mining, the horticultural industry is exploring alternative resources to use in substrates. Swine lagoon sludge (SLS) is an attractive option as it may provide nutrients needed to support plant growth, as well as using an agricultural waste product to address the peat shortage. A compost was developed using an in-vessel compost reactor to compost SLS with peanut hulls [15:85 (by volume) SLS:peanut hull] to produce a swine lagoon compost (SLC). A greenhouse transplant study was conducted with three species: basil (Ocimum basilicum ‘Dark Opal’), chives (Allium schoenoprasum), and dill (Anethum graveolens ‘Hera’) grown in three substrates: SLC, a commercially available organic potting substrate with a nutrient charge (OM), and a commercial peat-based potting substrate with a 2-week nutrient charge (PEAT). The average height for basil, chives, and dill was significantly greater at transplant harvest when produced in the SLC substrate compared with the OM and PEAT. Airspace was greatest for SLC and lowest for OM and PEAT. Although root growth was not measured in this study, more prolific root growth throughout the plug was observed with SLC compared with OM and PEAT possibly because of the greater airspace in SLC. Substrate solution pH did not change substantially over time, whereas electrical conductivity (EC) decreased from 0.24 to 0.14 mS·cm−1. Both substrate pH and EC were within acceptable ranges for transplant production. SLC provided the physical and chemical requirements for herb transplant production without any additional fertilizers or amendments.

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Rebecca L. Turk, Helen T. Kraus, Ted E. Bilderback, William F. Hunt, and William C. Fonteno

Twelve rain gardens were constructed to analyze the effectiveness of three different filter bed substrates to support plant growth and remove nutrients from urban stormwater runoff. The filter bed substrates included a sand-based substrate (sand) composed of (v/v/v) of 80% washed sand, 15% clay and silt fines, and 5% pine bark; a soil-based substrate (soil) composed of (v/v) 50% sandy loam soil and 50% pine bark; and a slate-based substrate (slate) composed of (v/v) 80% expanded slate and 20% pine bark. Coarse particles (6.3 to 2.0 mm) in the soil-based substrate created a large-pore network that conducted stormwater more quickly into and through the rain garden than slate or sand as evidenced by the high infiltration and saturated hydraulic conductivity values. Sand had good overall retention of pollutants except nitrogen (N) possibly as a result of the very small percentage (5%) of organic matter and low cation exchange capacity (CEC). Soil had the lowest remediation of phosphorus (P) and highest concentration of P in its effluent and was similar in N removal efficiency to slate. Slate had the best retention of N and P. Overall, all three substrates functioned in reducing the quantity of pollutants in urban stormwater runoff; yet, the impact of substrate on remediation appeared to lessen by Season 2 because there were few differences between substrate in the effluent nutrient concentration. Substrate did not affect shoot or root growth. Eleven of the 16 species (B. nigra, B. ‘Duraheat’, M. virginiana, M. ‘Sweet Thing’, I. virginica, I. ‘Henry’s Garnet’, J. effusus, P. ‘Shenandoah’, H. angustifolius, H. ‘First Light’, and E. purpureum subsp. maculatum) grew well in the rain gardens and could be used as rain garden plants.

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Ellen T. Paparozzi, Kimberly A. Williams, Robert Geneve, Harlene Hatterman-Valenti, Cynthia Haynes, Helen Kraus, Cynthia McKenney, and Joelle Pitts