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We investigated water loss of shade trees over turf and asphalt in an arid and humid climate for Russian olive and silver maple. Total daily tree water loss, and dawn-to-dusk stomatal conductance (gs) and leaf temperature (Tl), as well as air temperature, surface temperature, and vapor pressure deficit, were measured in Logan, Utah, and Stillwater, Okla., in early and mid-summer. Midday air temperatures in mid-summer were similar at both locations, 30 to 35 °C. Comparable vapor pressure deficits (VPD, kPa) were much higher in Logan, 3.5–5.0, than Stillwater, 2–2.5. Differences in humidity and air temperature between asphalt and turf were negligible at both Stillwater and Logan. Midday surface temperatures for asphalt and turf averaged 34 and 50 °C, respectively, in Logan, but were 10 °C higher for both surfaces in Oklahoma. The effect of higher longwave radiation from hotter surfaces on stomatal conductance and water loss of trees over asphalt in Stillwater was not consistently different for either species from those over turf. However, at Logan, Tl of trees over asphalt were consistently 2 to 4 °C higher and gs was 10% to 20% lower than those over turf. Stomatal closure for trees over asphalt resulted in water loss that was the same or slightly lower as trees over turf. The effect of paved surfaces on tree water loss appears to be more pronounced in an arid than a humid climate. The combined effect of higher VPD in an arid region and greater longwave radiation from hotter paved surfaces induces stomatal closure that limits water loss, and likely photosynthesis. By contrast, in humid regions, increased tree radiation interception over asphalt does not appear to trigger stomatal closure due to lower VPD.

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Woody plant species were treated in 1995 and 1996 with 0, 1, 2, or 4 lb/acre (0, 1.1, 2.3, or 4.5 kg·ha-1) propazine (a.i.). Species studied in 1995 included rose-of-sharon (Hibiscus syriacus L. `Double Purple'), japanese boxwood (Buxus microphylla Sieb. & Zucc. `Green Mountain'), butterfly bush (Buddleia davidii var. Veitchiana Rehd. `Nanho Purple'), euonymus (Euonymus fortunei var. acutis Hand-Mazz. `Emerald n'Gold'), forsythia (Forsythia ×intermedia Zab. `Lynnwood Gold'), fire thorn (Pyracantha angustifolia Roem. `Gnome'), and japanese spiraea (Spiraea japonica L.f. `Goldflame'). Crape myrtle (Lagerstroemia indica L. `Acoma' and `Zuni') and juniper (Juniperus chinensis L. `Pfitzeriana') were added and euonymus and japanese spiraea were omitted in 1996. In both years, statistical analyses revealed differences in height and visual quality between plants exposed to propazine and control plants of some species; however, differences were inconsistent in that some plants treated with propazine were larger or rated better than control plants while other plants were smaller or of lower quality than their corresponding control plants. In all cases, differences among propazine treatments within each species were <1.2 inches (3 cm) in height while decreases in visual quality compared to control plants were most evident in plants receiving four times the recommended rate of propazine. The horticultural significance of these differences was, therefore, considered small, suggesting that all of the species tested are tolerant to propazine applied at the recommended rate of 1 lb/acre (1.1 kg·ha-1). Chemical names used: 6-chloro-N,N'-bis(1-methylethyl)-1,3,5-triazine-2,4-diamine (propazine).

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Commercially propagated `Halward's Silver' spirea (Spiraea nipponica Maxim.) bareroot cuttings and cuttings with substrate around the roots (plugs) were transplanted into 3.8-L containers and fertilized with various P fertilizers to determine the effect of fertilizer source on P leaching and plant growth. The following fertilizer treatments were applied: 1) 100% of the recommended rate of P from controlled-release fertilizer (CRF), consisting of 22N-2.6P-10K; 2) 100% of P from triple superphosphate (TSP, 0N-20P-0K) with N and K provided by 22N-0P-10K CRF; and 3) 50% of P from CRF, consisting of 22N-1.3P-10K, plus 50% of P from TSP (CRF/TSP). The most P leached from cuttings transplanted as plugs or bareroot and fertilized with TSP, while the least P leached from cuttings transplanted as plugs and fertilized with CRF or CRF/TSP. Plants fertilized with CRF/TSP generally had larger root dry weights than did plants fertilized with CRF or TSP. Plants fertilized with CRF had the smallest stem dry weights. Shoot-to-root (S/R) ratio was largest in plants transplanted as plugs in substrate amended with TSP, but cuttings transplanted bareroot into CRF-amended substrate had the highest S/R ratio and the lowest stem P concentration. Incorporation of CRF/TSP into the container substrate can reduce P leaching compared with incorporation of TSP, and can increase root and stem dry weights of plants transplanted as plugs compared with incorporation of CRF.

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Spiraea japonica L. f. `Froebelii' were grown in 3.8-L containers filled with substrates consisting of recycled paper (RP) and pine bark at rates of 0%, 25%, 50%, 75%, or 100% (by volume) RP. Fertilizer treatments included 100% of the recommended rate of N as controlled release (CRF) or liquid fertilizer (LF) or both. The same amounts of N (as NO3 --N and NH4 +-N), P and K were supplied with each fertilizer treatment. Plants were irrigated in Fall 1996 based on substrate water-holding capacity and to achieve a 25% to 50% leaching fraction. In Spring 1997 regardless of substrate water holding capacity, plants were irrigated weekly initially, then twice weekly later in the study when plants were larger. Fertilizer treatment did not affect plant size, but plant diameter and shoot and root dry weight decreased as substrate RP concentration increased in Fall 1996. All plant size parameters measured decreased as substrate RP concentration increased regardless of fertilizer treatment in Spring 1997. In Fall 1996, shoot and root N concentration increased as CRF decreased (and LF increased), but substrate RP concentration did not affect shoot or root N concentration. In Spring 1997, shoot and root N concentration generally decreased as substrate RP concentration increased with 50% CRF, 50% LF, or 100% LF. Leachate NO3 --N, NH4 +-N and total N generally increased as CRF decreased but decreased as substrate RP concentration increased in both years. Substrate volume and percentage of air space decreased, but bulk density increased, as RP concentration increased. Although N leaching decreased as substrate RP concentration increased in both years, reasonable plant growth occurred only in those substrates containing ≤50% RP.

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These studies were conducted to determine the effect of 1) temperature on P leaching from a soilless medium amended with various P fertilizers, 2) water application volume on P leaching, and 3) various fertilizers on P leaching during production and growth of marigolds (Tagetes erecta L. `Hero Flame'). Increasing temperature linearly decreased leaching fraction; however, total P leached from the single (SSP) or triple (TSP) superphosphate-amended medium did not differ regardless of temperature. Despite a smaller leaching fraction at higher temperatures and no change in the total P leached, P was probably leached more readily at higher temperatures. More P was leached from the medium amended with uncoated monoammonium phosphate (UCP) than from the medium containing polymer-coated monoammonium phosphate (CTP) at all temperatures, and more P was leached from UCP-amended medium at lower temperatures than at higher temperatures. More P was leached from TSP- than from SSP-amended medium and from UCP- than from CTP-amended medium regardless of the water volume applied, but leachate P content increased linearly as water application volume increased for all fertilizers tested. Plant dry weights did not differ regardless of P source. Leachate electrical conductivity (EC) was lower with TSP than with SSP. Leachate EC was also lower with CTP than with UCP. A higher percentage of P from controlled release fertilizer was taken up by plants rather than being leached from the medium compared to P from uncoated fertilizers.

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Wet Earth (WE) is a recycled paper product that may substitute for peat moss as a growth substrate. WE is available at various pH levels and may be formulated using: 1) paper production byproducts (WES), or 2) recycled corrugated cardboard (WEC). Use of WE by commercial growers would reduce demand for both landfill space and for slowly renewable resources such as peat and pine bark. Experiment objectives included: analyzing plant performance of azaleas (Rhododendron obtusum `Hino Crimson') in WE-based growth substrates at pH 3.4 and pH 6.6 and in peat-based growth substrates (Trial pH), 2) analyzing plant performance of WES, WEC, and peat moss-based growth substrates (Trial SC), and 3) determining changes, if any, in substrate physical properties from planting to harvest. Shadehouse experiments were conducted in summer of 1996. Ratios of pine bark to WE tested were 100% pine bark, 1:3, 1:1, 3: l, and 100% WE by volume. Plant heights, widths, and visual quality ratings were obtained monthly throughout the 16-week experiment. Leaf, shoot, and root dry weights and leaf nitrogen concentration were determined at harvest. Changes in volume, bulk density, porosity, and air space were also measured. Plants performed poorly in WES, pH 3.4, with mortality exceeding 90%. Peat and WEC yielded similar (and best) results. Optimum plant performance for all substrates occurred in 1: 3 and 1: 1 (WE: pine bark) mixes. At concentrations over 50%, increases in bulk density and reductions in volume and percent air space in WE substrates were severe enough to negatively impact root growth and plant quality.

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Wet Earth (WE) is a recycled paper product being tested as a potential plant growth substrate. It is composed of 80% recycled paper, 18% diatomaceous earth, 1% CaO, and 1% humic acid by volume. Use of WE by commercial growers would reduce demand for both landfill space and for slowly renewable resources such as peat and pine bark. Evidence also suggests that WE reduces nitrate runoff. Objectives included: determining effects of WE on plant growth, examining effects of WE on NO3 and NH4 runoff from container plant production, and determining the chemical and physical properties that characterize WE as a growth substrate. Ratios of pine bark to WE tested were 100% pine bark, 1:3, 1:1, 3:1, and 100% WE by volume. Fertilizer treatments included: 100% of the recommended rate of controlled release fertilizer (CRF), 50% CRF plus 50% liquid fertilizer (LF) and 100% LF. Plant heights, widths, and visual quality ratings were obtained monthly throughout the 16-week experiment. Leaf, shoot and root dry weights were determined at harvest. Nitrogen content of roots, shoots, and substrates were determined at planting and harvest, while NO3 and NH4 content of leachate was determined at each irrigation. All substrates were analyzed at planting and harvest for pH, soluble salts, exchangeable cations, and CEC. Changes in volume, bulk density, porosity, and air space were also measured. Plant size and quality varied significantly between substrate mixes. Mortality was significantly higher in mixes containing 75% and 100% WE. Changes in volume, bulk density, and percent air space were also significant and inversely related to WE concentration.

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Euonymus fortunei (Turcz.) Hand.-Mazz. is susceptible to anthracnose caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. Fungicides have provided little control of anthracnose on E. fortunei in past studies. Identification of cultural practices that reduce disease incidence would be beneficial to the nursery industry. Containerized E. fortunei `Emerald'N Gold' plants were placed either on gravel beds or black plastic-covered gravel beds. Half of the beds in each bed treatment were sprayed with a 10% bleach solution monthly to attempt to reduce the presence of C. gloeosporioides inoculum. Plants were rated monthly from May (initial rating) through October for disease severity. A covariate analysis was performed using initial ratings as the covariate for ratings from all other months. Bleach did not affect disease ratings at any time. Disease ratings of plants on plastic-covered beds were lower than those of plants on gravel beds. Disease ratings decreased linearly as the growing season progressed.

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WetEarth, a processed recycled newspaper product, was used in combination with pine bark, sand, and vermiculite as a growing medium for rose of Sharon and forsythia. Rose of Sharon was taller and had more leaves; more leaf area per plant; and greater leaf, stem, and root dry weights in all media containing recycled paper compared to plants grown in a medium consisting of 3 pine bark: 1 peat moss: 1 sand (by volume) (control). Forsythia grown in the control media were taller than those grown in any medium containing recycled newspaper. There was no difference in number of leaves per plant or leaf area of forsythia, regardless of growing medium. Physical and chemical properties of each medium also were investigated. All media containing recycled newspaper had a higher pH, porosity, and air space than the control medium.

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