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Diana R. Cochran, Charles H. Gilliam, Glenn Fain and Robert D. Wright

This study evaluated the effects of nine alternative substrates on herbicide efficacy in container-grown nursery crops: 1) VT (pine wood chips hammer-milled to pass a 0.4-cm screen); 2) USDA (pine wood chips hammer-milled to pass a 0.64-cm screen; 3) AUC (Pinus taeda chipped including needles); 4) AUHM (AUC hammer-milled to pass a 0.48-cm screen; 5) 1 VT: 1 commercial grade pinebark (v/v); 6) 1 USDA: 1 pinebark (v/v); 7) 1 AUC: 1 pinebark (v/v); 8) 1 AUHM: 1 pinebark (v/v); and 9) 6 pinebark: 1 sand (v/v). Each substrate was amended with 6.35 kg of 17–6–12 (17N–2.6P–10K) control-release fertilizer, 2.27 kg of lime, and 0.89 kg micromax per cubic meter. Containers (8.3 cm) were filled on 15 June and three herbicides applied the next day: Rout (oxyfluorfen + oryzalin at 2.24 + 1.12 kg·ha-1), Ronstar (oxadiazon at 4.48 kg·ha-1) and a nontreated control. The next day, containers were overseeded with 25 prostrate spurge seed. Data collected included weed counts 30 and 60 days after treatment (DAT) and weed fresh weights at 60 DAT. Spurge occurred less in the two treatments of 100% pine wood chips followed by the AUC treatment. With spurge, the least weed fresh weight occurred with the USDA and AUC treatments. For example, at 30 DAT, spurge count was reduced by 33%, 40%, and 70%, respectively, when comparing VT, USDA, and AUC to pinebark: sand. Spurge fresh weight at 60 DAT followed a similar trend. With all of the substrates except AUHM, the addition of commercially used pine bark resulted in less weed control. Rout provided superior control followed by Ronstar and the nontreated control. These data show that control of prostrate spurge with commonly used preemergent applied herbicides may actually be improved with some of the alternative substrates currently being tested.

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Alison A. Stoven, Hannah M. Mathers and Daniel K. Struve

The mineral nutrition requirements and fertilizer application methods for container-grown shade tree whips are not well understood. This experiment was conducted to determine the effects of fertility method (water soluble vs. controlled release) on growth, water, and N use efficiency of four taxa [(Acer ×freemanii `Jeffersred' (Autumn Blaze® maple), Cercis canadensis L. (Eastern redbud), Malus (Mill.), `Prairifire' (Prairifire crabapple), and Quercus rubra L. (red oak)] in two production environments [outdoor gravel pad vs. a retractable roof structure (RRS)]. No single fertilizer method consistently resulted in the greatest growth. In the RRS, maple and crabapple heights, and crabapple and redbud caliper were larger when whips were fertilized with controlled-release fertilizer (CRF); outdoors, CRF resulted in taller maples and larger caliper crabapples. However, in the RRS, maple whips fertilized with water-soluble fertilizer had higher production water use efficiency than those fertilized with CRF, whereas crabapple whips had higher N use efficiency when fertilized with CRF. Nitrogen use efficiency was higher for redbud and crabapple whips fertilized with CRF than with CRF. Outside, crabapple whips fertilized with CRF had higher production water use efficiency than those fertilized with water-soluble fertilizer. There were no differences in N use efficiency attributed to fertilizer method. When averaged over fertilizer application methods, height, caliper, water, and N use efficiency were greater when whips were grown in RRS than outdoors. There were two exceptions: Maple caliper and production water use efficiency were marginally higher when whips were grown outdoors. The greater growth for whips produced in the RRS was attributed to reduced ambient and substrate temperature stress.

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Hannah Mathers

Weed growth in container-grown nursery stock is a particularly serious problem. Inexpensive and easily accessible carriers for safe application of concentrated preemergent herbicides have been investigated. Monaco and Hodges (1974) evaluated standard pine bark used in potting media. Coating broadcast fertilizers with preemergents has also been recently examined in agronomic crops (Koscelny and Peeper, 1996; Rabaey and Harvey, 1994). The four objectives of this experiment were: 1) determine the efficacy and duration of weed control of a range of preemergent herbicide-impregnated carriers, applied as a top-dressing. The preemergents to be tested are: Goal, Surflan, Rout, Gallery, Gallery/Surflan, Ronstar and Regal 0; 2) determine the efficacy and duration of weed control of a range of preemergent herbicide-impregnated slow and controlled release fertilizers, applied preplant incorporated in the potting mix; 3) assess the phytotoxicity of the chemical-treated carriers on the ornamental plants evaluated; and 4) determine which weeds were controlled. Of the carriers investigated, bark was the best treatment regardless of pre-emergent used. However, Surflan and Gallery were slightly better than Goal. The effectiveness of the bark in controlling weeds is worth investigating in further studies. A significant species effect with the efficacy data was observed. Euonymus `Emerald Gaiety' was significantly better at competing with the weeds present than the other species evaluated. Top dressing gave significantly fewer weeds, with rated data, vs. incorporation. The effect was most pronounced for Kansel or Fert. plus Ronstar. Osmocote micro-fert. gave less weeds, top-dressed, when weed weights were analyzed. However, using the weed weight data, there were no significant differences whether the carriers were applied top dress or incorporated. Phytotoxicity was not significantly different with incorporation vs. top dressing.

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Amy N. Wright, Alex X. Niemiera, J. Roger Harris and Robert D. Wright

The objective of this study was to determine the effect of micronutrient fertilization on seedling growth in pine bark with pH ranging from 4.0 to 5.5. Koelreuteria paniculata (Laxm.) was container-grown from seed in pine bark amended (preplant) with 0, 1.2, 2.4, or 3.6 kg/m3 dolomitic limestone and 0 or 0.9 kg/m3 sulfate-based micronutrient fertilizer (Micromax ®). Initial pine bark pH for each lime rate was 4.0, 4.5, 5.0, and 5.5, respectively. Final pH (week 10) ranged from 4.7 to 6.4. Ca and Mg supply in irrigation water was 10.2 and 4.2 mg·L–1. Seedlings were harvested 10 weeks after planting, and shoot dry weight and height were determined. Pine bark solution was extracted using the pour-through method at 3, 7, and 10 weeks after planting. Solution pH was measured, and solutions were analyzed for Ca, Mg, Fe, Mn, Cu, and Zn. Shoot dry weight and height were higher in micronutrient-amended bark than in bark without added micronutrients. Lime (1.2 kg·\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{m}^{-_{3}}\) \end{document}) increased growth only in the absence of micronutrient additions. In general, adding micronutrients increased pine bark solution Ca, Mg, and micronutrient concentrations. Adding lime increased pine bark solution pH and Mg concentration and either had no effect on or decreased solution Ca and micronutrient concentrations. Regardless of pine bark pH, micronutrient additions resulted in improved growth and adding lime was not necessary.

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J.D. MacDonald

Cuttings of Dendranthema ×grandiflorum `Paragon' were used as a model system to assess the effects of root heating on disease severity. Roots were exposed to single episodes of heat stress, after which they were inoculated with zoospores of Phytophthora cryptogea Pethyb. & Laff. Root damage resulting from heat stress, or heat stress plus Phytophthora, was quantified 5 to 7 days after treatment. Roots of hydroponically grown plants, immersed for 30 min in aerated, temperature-controlled nutrient solutions, were severely damaged at 45C or above. Relatively little phytophthora root rot developed on inoculated plants exposed to 25 or 35C, but infection was severe in roots heated to 40C. Plants grown in potting mix were exposed to heat stress by plastic-wrapping the containers in which they were growing and placing them in heated water baths until roots achieved desired temperatures for 30 min. This system heated roots more slowly than in the hydroponic experiments, and 45 and 50C were less damaging. The amount of Phytophthora-induced root damage was insignificant in containerized plants heated to 25 or 35C, but was highly significant in those heated to 40C or higher. In field experiments, plants were positioned so their containers were either fulIy exposed to the late afternoon sun or heavily shaded to prevent sun exposure. The root zones of sun-exposed pots heated to 45 to 47C, while those of shaded pots never exceeded 34 to 36C. There was a large, highly significant increase in phytophthora root rot severity in the sun-exposed pots compared to shaded plants. These experiments showed that temperatures of 40C or higher, which commonly occur in container-grown plants exposed to solar radiation, can predispose chrysanthemum roots to severe Phytophthora infection.

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Jo-Ann Bentz and Alden M. Townsend

The suitability of container-grown clones of red maple, Acer rubrum L., as a host to the potato leafhopper, Empoasca fabae Harris (Homoptera: Cicadellidae), under different fertilization regimes was determined, and compared to different freeman maple cultivars (A. ×freemanii E. Murray). Three clonal selections of red maple (USNA numbers 56026, 59904, and 55410), and three freeman maple cultivars (55892 `Indian Summer', 67256 `Jeffersred' [trademark Autumn Blaze], and 55890 `Armstrong') were potted in 7.6-L containers, fertilized with either 0, 3.3, or 6.6 g/pot of calcium nitrate and used in experiments. When given a choice, female leafhoppers laid more eggs on leaves of red maple clone 56026 than on leaves of clone 59904, with oviposition linearly increasing on both clones with increases in the fertilization level applied to the trees. Yet, when female leafhoppers were confined to leaves using organza sleeve cages, oviposition increased linearly as fertilizer level increased, without a significant clonal effect. Oviposition did not differ among freeman maple cultivars, nor was it influenced by the fertilizer level applied to the freeman maple trees. Nymphs had the lowest odds of surviving to adulthood when reared on the freeman maple `Jeffersred', but highest when reared on red maple 59904. Red maple 59904 had the fastest growth rate while red maple 55410 had the slowest. Leaf initiation and expansion in red maple 56026 was significantly slower than in the other selections. Leaf development of these three red maple clones was significantly accelerated by the application of fertilizer, regardless of level. The maple selections differed in their mean amounts of foliar macronutrients and micronutrients, which related to the fertilizer level applied to trees. Unfertilized trees had the highest C to N ratio, which decreased as fertilizer level applied to trees was increased. This study showed that fertilization improved the performance of the potato leafhopper on previously nonpreferred maple selections, and that the foliar nutrient content and C to N ratio could be used as indicators of tree susceptibility to insect attack under different growing conditions.

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Mohammed Z. Alam, Calvin Chong, Jennifer Llewellyn and Glen P. Lumis

water use and runoff from container growing. In Ontario, controlled-release fertilizers (CRFs) are most commonly used to fertilize container-grown plants. CRF is commonly incorporated into the medium before potting or topdressed on the surface of the

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Carolyn F. Scagel, Guihong Bi, Leslie H. Fuchigami and Richard P. Regan

Improved fertilization guidelines and more effective fertilizers need to be designed to optimize nutrient use efficiency and to minimize leaching in production of container-grown nursery plants. Container-grown plants are often fertilized with

Open access

Jeff B. Million and Thomas H. Yeager

calculations. ET LF was the reference potential ET value (ETo) calculated using the 24 h of weather data collected before the input LF test date and time. ETo was calculated using a container-grown plant evaporation model ( Million et al., 2011 ), which used a

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Dewayne L. Ingram, John M. Ruter and Chris A. Martin

examination. It is essential to know the critical RZT that cause direct injury to root tissues when considering methods to reduce heat stress in container-grown plants. Unless modifications can maintain RZT below the critical threshold, such production