Nursery Crops Research Articles

Loop-mediated isothermal amplification detection of Phytophthora kernoviae, Phytophthora ramorum, and the P. ramorum NA1 lineage on a microfluidic chip and smartphone platform.

Rapid, field-deployable assays such as loop-mediated isothermal amplification (LAMP) are critical for detecting nursery and forest pathogens like Phytophthora ramorum and P. kernoviae to prevent pathogen spread. We developed and validated four LAMP assays for genus-level detection of Phytophthora spp., species-level detection of P. kernoviae and P. ramorum and lineage-level detection of the P. ramorum NA1 lineage. Cross reactivity of the two species-specific LAMP assays was evaluated using a set of 18 Phytophthora spp. known to infect nursery crop hosts. The correct target species were detected by the species-level LAMP assays. The Phytophthora spp. LAMP assay was evaluated against 27 Phytophthora spp. and other bacterial and fungal pathogens and reacted with all the Phytophthora spp. evaluated but no other bacterial or fungal species. The limit of detection (LOD) of the P. kernoviae LAMP was 100 fg/µl and the LOD of the P. ramorum LAMP assay was 1 pg/µl of DNA. The NA1 LAMP assay was tested against the NA1, NA2, EU1, and EU2 lineages of P. ramorum and was lineage-specific but had a higher LOD (100pg/µl) than the species-specific LAMP assays. Both P. ramorum and P. kernoviae LAMP assays were highly precise (>0.94) in detecting the respective pathogens in symptomatic rhododendron leaves and co-inoculation experiments. The set of four LAMP assays were run in tandem on a microfluidic chip and smartphone platform and can be used in the field to detect and monitor spread of these regulatory Phytophthora spp. in forest and/or nursery settings.

Genetic control of Fusarium circinatum tolerance in Pinus patula × P. tecunumanii hybrid families

The pine pitch canker fungus, Fusarium circinatum, has caused large-scale mortality of Pinus patula crops in South African nurseries and high in-field post-planting mortality. Tree breeders have identified selection and breeding of tolerant material as the likely long-term solution to this disease. In this study, the greenhouse artificial inoculation screening method was employed to investigate the genetic control of F. circinatum tolerance in a factorial mating design of Pinus patula × P. tecunumanii low elevation (PPTL) and high elevation (PPTH) hybrid families and their parental species. Results indicated that F. circinatum tolerance is under moderate genetic control (h 2 between 0.13 and 0.36) as assessed in a hybrid factorial mating design with a large number of PPTL and PPTH families. The PPTL hybrid displayed the highest level of tolerance, followed by pure P. tecunumanii LE, then the PPTH hybrid, pure P. tecunumanii HE and lastly pure P. patula. A general hybridising ability (GHA) and specific hybridising ability (SHA) analysis was also conducted to rank parent families as well as hybrid families. These breeding values can be used to identify superior families for commercial production and further breeding. A poor correlation between frost tolerance and F. circinatum tolerance was also found when compared to a previous frost tolerance study utilising the same hybrid families. The results from this study indicated that it is possible for breeders to cross selected P. patula seed parents with selected P. tecunumanii pollen parents to develop F. circinatum tolerant hybrid families for commercial production.

How Natural Resources, Consumer Perceptions, and Labor Are Transforming the US Nursery Industry

The nursery industry produces and sells plants for landscape and environmental purposes and represents a major sector within the US agricultural industry. In recent years, the nursery industry has undergone rapid growth as a result of various factors, including increased demand from housing development and pandemic-fueled interest in home horticulture. As with any industry, the nursery industry must adapt to changes in societal trends to sustain growth. In the wake of unprecedented societal and supply chain issues stemming from the global coronavirus disease 2019 pandemic, the American Society for Horticultural Science Nursery Crops Professional Interest Group gathered experts in various disciplines to provide their opinions and insights into the future of the nursery industry, focusing specifically on the changes and challenges the nursery industry will face in the coming decade. Nursery crop specialists spanning the United States identified three primary areas that will steer the future momentum of the nursery industry: consumer trends, natural resources, and labor. Six experts were selected to represent these areas in a workshop held Jul 2022 at the American Society for Horticultural Science Annual Conference in Chicago, IL, USA. This article was developed to disseminate to the greater scientific community the discussions held and insight shared during that workshop.

A Base Layer of Ferrous Sulfate-Amended Pine Bark Reduces Phosphorus Leaching from Nursery Containers

Phosphorus (P) fertilizers applied to container-grown nursery crops readily leach through pine bark-based substrates and can subsequently runoff and contribute to surface water contamination. The objectives of this research were to determine the effect of adding a layer of FeSO4·7H2O-amended pine bark (FSB) to the bottoms of nursery containers on P leaching characteristics. Phosphorus and iron (Fe) leaching in response to FSB layer height (4 or 7.5 cm), FeSO4·7H2O rate (0.3, 0.6, or 1.2 kg·m−3 Fe), and form (i.e., granular versus liquid) used to formulate the FSB layer, and the inclusion of dolomite in the FSB layer were also investigated. Greenhouse studies lasting 15 and 19 weeks were conducted, in which 2.5 L nursery containers containing the FSB layer treatments below non-amended pine bark substrate were fertilized with 199 or 117 mg P from a soluble or controlled-release fertilizer, respectively. Leachate resulting from daily irrigation was collected and analyzed for P and Fe weekly. All FSB treatments leached less P than the control (non-amended pine bark only), with P reductions ranging from 22% (4 cm FSB with 0.3 kg·m−3 Fe) to 73% (7.5 cm FSB with 1.2 kg·m−3 Fe). Phosphorus leaching decreased linearly with an increase in Fe rate or layer height. The amount of Fe that leached from containers with FSB was <5% of that applied, regardless of the Fe rate. Granular- and liquid-applied FeSO4·7H2O with or without dolomite were equally effective at reducing P leaching. Adding 0.6 kg·m−3 Fe to the bottom 500 cm3 of pine bark increased P adsorption by 0.053 mg·cm−3 P, which equates to 17.9 mg P adsorbed per gram of FeSO4·7H2O added. Results from this research suggest that including an FSB layer in the bottom of nursery containers is an effective strategy for reducing P runoff from container-based nursery production sites.

Genome Doubling of Northern Spicebush, Lindera benzoin L.

Lindera benzoin is a dioecious understory shrub native to eastern North America. Northern spicebush is a beautiful shrub with a natural round shrub shape, golden-yellow fall foliage, attractive bright red drupes, and precocious yellow flowers in early spring; however, its market value as an ornamental value has been overlooked. To improve the ornamental values of this under-cultivated nursery crop, breeding for a better compact form, larger leaves, enlarged flower clusters and fruit, and increased stress tolerances could all be beneficial. Polyploidy manipulation is a valuable method to improve such traits for many ornamental plants. This study established the genome doubling method by oryzalin-infused solid agar treatment on young northern spicebush seedlings. The seedlings of two wild populations in North Carolina were collected and used. A total of 288 seedlings were treated with solid agar containing 150 µM oryzalin for 24, 72, and 120 h. The results were sporadic in their survival ratios and tetraploid conversion ratios between different treatments; however, a total of 16 tetraploid L. benzoin plants were produced in this study. The 24-h treatment showed the optimal result, with 7.1% of total treated seedlings or 15.2% of surviving seedlings converted into tetraploids. Tetraploid plants had visible differences in leaf morphology, a statistically significant enlarged stomata size, and reduced stomatal density compared to diploid plants. This research provides ploidy manipulation information for all future breeding processes of L. benzoin and related species.

Life cycle assessment of citrus tree nurseries in Uruguay: Are their environmental impacts relevant?

Perennial fruit production at the commercial scale, such as citrus fruits, begins with seedling production in a nursery. This stage lasts several months and involves different phases and the use of substrates and infrastructure. As the seedling does not produce fruit but does consume inputs, studying the environmental impacts associated with this stage becomes relevant, especially to understand its contribution to the total impact of the crop cycle. Despite the global relevance of fruit tree seedlings production, LCA studies in the literature focus on horticultural crop nurseries, and those on perennial tree nurseries do not consider both substrate and structures in the analysis, which is key for this type of crop since the main production system is soilless production in greenhouses. Thus, the main goal of this study is to quantify the environmental impacts related to the production of citrus fruit tree seedlings using LCA, analyse the main production system applied nowadays, and study its relevance with respect to the crop cycle. To this end, a certified Uruguayan citrus nursery was analysed, from which primary data was obtained. As well, methodological issues concerning water consumption and modelling emissions from input applications in soilless greenhouse systems are tackled. Results show that the main hotspots of the nursery stage are infrastructure production and peat transportation, which highlights the relevance of their inclusion when modelling the system. Extending the lifespan of the galvanised steel structures and decreasing substrate transport distances are shown to be effective measures to reduce environmental impacts. The contribution of the nursery stage to the citrus production cycle is negligible for almost all the impact categories assessed except cancer human toxicity, as it accounts for 0–3.6% of the impacts depending on the impact category. Great differences (from 10 to 400 times higher results on average) are observed when comparing the results with those from commercial databases, as they consider open-field nurseries where seedlings are grown in the soil. The need to develop harmonised methods to model water consumption and fertiliser and pesticide emissions for soilless crops in greenhouses arises. The present study presents a complete quantification of the environmental impacts of the main production system of citrus fruit tree seedlings and provides scientific and quantitative evidence of its contribution to the production cycle, helping decision-makers understand where efforts should be focused to achieve a more sustainable fruticulture.

Effects of Insecticide Drench Application against Immatures of Systena frontalis in Container-grown Hydrangea paniculata

Systena frontalis (F.) (Coleoptera: Chrysomelidae), commonly referred to as the redheaded flea beetle, is a serious pest in container nurseries, as adult feeding defoliates nursery crops and affects plant salability. Because the foliar application of insecticides provides inconsistent efficacy, additional and alternative control tactics are sought to target immatures of this pest in growing media. Thus, the objective was to determine the effects of non-neonicotinoid insecticides applied as a drench to growing media on immatures of S. frontalis. In 2021 and 2022, nine active ingredients were evaluated in four trials in a Georgia nursery and at a Virginia research and extension center. If available, the maximum label rates for flea beetles or other coleopteran pests were applied once to Hydrangea paniculata Siebold containers (11.4 L, 3 gal) as a drench application. The emergence of S. frontalis adults from treated growing media and foliar feeding damage was lower for the tetraniliprole (TetrinoTM) and spinetoram + sulfoxaflor (XXpire®) treatments than for nontreated plants. Cyclaniliprole (SarisaTM) and chlorantraniliprole (Acelepryn®) suppressed S. frontalis adult eclosion with less feeding damage than the nontreated plants. Tetraniliprole, spinetoram + sulfoxaflor, and cyclaniliprole are not labeled for drench application. Dinotefuran (Safari®) effectively reduced adult emergence and feeding damage. Species used in this study: Redheaded flea beetle, Systena frontalis (F.); panicled hydrangea, Hydrangea paniculata Siebold. Chemicals used in this study: Cyantraniliprole (Mainspring®GNL), chlorantraniliprole (Acelepryn®), tetraniliprole (TetrinoTM), cyclaniliprole (SarisaTM), Spinetoram + Sulfoxaflor (XXpire®), tolfenpyrad (Apta®), Chromobacterium (Grandevo®CG), flupyradifurone (AltusTM), dinotefuran (Zylam® Liquid, Safari® 20G), and polyterpenes pinene (NuFilm® P).

Organic Hydromulches in Young Olive Trees in Pots: Effects on Soil and Plant Parameters

Organic hydromulches (liquid spray-on mulches) have been used traditionally in land rehabilitation, mainly to mitigate post-fire runoff and erosion. However, in recent years, a new application of these materials as an eco-friendly alternative to the widely used polyethylene mulch, both in vegetable and woody crops, has been studyied. This work analyzes the effects of six hydromulches, based on organic by-products, on different soil parameters (water content, temperature, and CO2 flux), plant–water relations (stem water potential, leaf gas exchange, and leaf temperature), and the growth (trunk diameter) of young olive trees planted in large pots in the open field over a 2-year trial. The hydromulches tested were: rice husk (RH), rice husk with linen oil (RHL), mushroom substrate (MS), wheat straw (WS), pistachio (PW), and vineyard (VW) pruning wood chips, mixed with different additives (gypsum, recycled paper paste, and Kraft fiber). A non-mulched manual weeding control (NM) was included. The results indicated that hydromulches, in comparison with NM, resulted in increased volumetric soil water content (on average, 22.9% in hydromulches and 19.5% in NM), reduced soil temperature fluctuations (4.97 °C in hydromulches and 6.13 °C in NM), and increased soil CO2 fluxes (0.80 and 0.49 g CO2 m−2 h−1, respectively). Although the differences in the soil water content did not have an obvious effect on the plant–water status, crop growth was reduced in NM (≈23% lower than PW, MS, RHL, and WS), suggesting that vegetative growth, especially in young olive trees, is extremely sensitive to water deficit. The overall study leads to considering hydromulches as a good alternative to mulching in large pots, especially PW, which would be useful for nursery crops before their final establishment in the field.

Microbial Community Structure in Soilless Substrates Used for Nursery Crops

Soilless substrates are widely used for plant cultivation. However, little is known about how soilless substrate components, plant growth, or their interactions impact microbial communities in soilless media. The objectives of this study were to analyze microbial communities in typical pine bark substrates used for nursery crop production and determine the impacts of substituting peat with a compost substrate, and planting, on microbial community dynamics over a production cycle. Three soilless substrate mixtures were compared. The substrate mixes consisted of 80:20:0, 80:10:10, and 80:0:20 (volume:volume:volume) ratios of pine bark:peatmoss:leaf compost, respectively. One set of each treatment was planted with a single birch (Betula nigra ‘Cully’) liner and another set was not planted. The treatments (n = 3) were maintained in a nursery production setting, and samples were taken after 0, 1, 2, 3, and 4 months. Bacterial and fungal communities were characterized by sequencing polymerase chain reaction-amplified 16s rRNA genes and internal transcribed spacer regions. Initially, the two substrate mixtures that contained compost had more phyla than the substrate mixture that only contained peat and bark. After 1 month, microbial communities in all treatments contained similar phyla, but at different relative abundances based on the amount of compost they contained. Over time, Nitrosomonadaceae and Acetobacteraceae were the most abundant bacterial families in substrate mixes containing 10% and 20% compost, but they were absent from treatments without compost. The communities were dynamic and changed the most over the first 2 months. Microbial communities and their dynamics were similar between planted and unplanted treatments. Planting had less of an effect on microbial communities than compost amendment. Among the fungal communities, differences were observed based on both compost amendment and plant presence. Ascomycota and Basidiomycota were the most abundant fungal phyla and resembled those originally in the peat and compost, respectively. These findings could be used to understand the importance and dynamics of specific microbial communities present in substrate components and how they develop during greenhouse production.

Key Plant, Key Pests: Southern Yew (Podocarpus macrophyllus)

This publication provides information and general management recommendations for dieback, fusarium wilt, root nodules, root rot, aphids, eriophyid mites, and scale. For a more comprehensive guide of woody ornamental insect management, download "Professional Disease Management Guide for Ornamental Plants" (http://edis.ifas.ufl.edu/pp123) or the "Integrated Pest Management in the Commercial Ornamental Nursery" guide (https://site.caes.uga.edu/sehp/files/2020/03/UF-IPM-in-the-Commercial-Ornamental-Nursery.pdf). Additional information on pest management can be found in the 2017 Southeast Pest Control Guide for Nursery Crops and Landscape Plantings (https://content.ces.ncsu.edu/southeastern-us-pest-control-guide-for-nursery-crops-and-landscape-plantings).

Greater rate of nitrogen fertilizer application increases root rot caused by Phytophthora cinnamomi and P. plurivora in container‐grown rhododendron

AbstractPhytophthora root rot, caused by many Phytophthora species, decreases the health of rhododendrons produced in nurseries. Optimizing nitrogen (N) fertilizer is often used to improve nursery stock quality, but there is little information on how N fertilizers influence root rot caused by these pathogens. To understand the impact of N fertilizer and pathogen species on root rot development, rhododendrons were grown with no (0 g N/pot), low (1.04 g N/pot) or high (3.12 g N/pot) rates of N and inoculated with either P. cinnamomi or P. plurivora. Noninoculated plants at low and high N rates had greater biomass, leaf greenness and enhanced N, potassium, magnesium, phosphorus, sulphur and manganese uptake compared to plants grown with no N. When either Phytophthora species was present, N application increased aboveground disease symptoms (wilting, chlorosis, reduced stomatal conductance and biomass), but had no effect on root rot severity belowground. In addition, P. cinnamomi restricted uptake of several nutrients while P. plurivora had less influence on nutrient uptake. Nurseries frequently apply high amounts of N to promote fast growth. However, our results show that this can exacerbate root rot when P. cinnamomi or P. plurivora is present. Although decreasing N can reduce the number of overtly symptomatic plants, this may conversely increase the risk for selling apparently asymptomatic plants with low levels of infection. Additional studies are needed to determine how N fertilization influences Phytophthora root rot for a broader range of rhododendron cultivars and nursery crop species.

Combating an Invasive Boxwood Pathogen - Calonectria pseudonaviculata - in the United States by Shifting Production to Less Susceptible Cultivars.

Boxwood Blight (BB) caused by Calonectria pseudonaviculata (Cps) is an economically devastating disease affecting the entire boxwood supply chain from growers to gardeners, since it was first officially documented in the United States in 2011. This disease has taken a heavy toll on boxwood, an iconic landscape plant and the number one evergreen nursery crop. The objective of this study was to examine the adoption of one sustainable management strategy available to growers: shifting boxwood production from highly susceptible to less susceptible cultivars. We investigated the ongoing shift by comparing boxwood sales of 17 selected nurseries from seven states across the country in 2011, 2016 and 2021. Results revealed that from 2021 to 2016, sales of cultivars highly susceptible to BB were reduced by over 35% while less sales of less susceptible boxwood cultivars increased 55%. Increased boxwood sales have been seen for 'Winter Gem', 'Wintergreen', 'SB 300' (Freedom®), 'SB 108' (Independence®), and 'Little Missy', all of which have been rated less susceptible than B. sempervirens 'Suffruticosa' in numerous trials. The potential for long-term positive impact on sustainable boxwood production and plantings in the U.S. through the use of such less susceptible cultivars is discussed. Better boxwood cultivar choices will build crop health into new plantings and sustain customer demand for boxwood. This is a case study for how sustainable crop protection strategy helps to maintain production of a crop under serious pressure from an invasive pathogen.

The Effectiveness of Phytosanitary Treatments in the Control of Oak Mildew, in the Current Climate Context

In the technical process of afforestation, most of the compositions require the act of founding the new forest artificially produced seedlings. In some situations, obtaining them is a difficult process due to the complex diseases and pests that can cause significant losses in nurseries. Climatic factors influencing the health of crops in nurseries are: air temperature, amount of precipitation, atmospheric humidity, potential evapotranspiration. The data were recorded with the help of the CEM DT 172 device, with the help of which data regarding temperature and humidity were recorded within the Beclean and Valea Iușului Nurseries. It was observed that the experiments related to the control of the pathogen Oidium alphitoides, using Proquinazid 200gr/l were placed in three cultures, one one-year-olds and two two-year-old, the amount of solution being the same in each variant, differing only the concentration and effectiveness was performed on four degrees of attack. The situation was positively reflected at the time of determining the effectiveness, when, except for the control variant, in all the treated variants most seedlings were weakly or moderately attacked.

Light Reduction, Banding, and IBA Treatments Influence Adventitious Rooting of Lindera benzoin Stem Cuttings

An investigation was undertaken to determine whether various light reduction and shoot banding treatments could increase rooting on stem cuttings of Lindera benzoin [(L.) Blume] (northern spicebush), a difficult-to-root woody plant. Stock plants were grown under one of three light conditions (light, shade, or etiolation). Emerging shoots received either no treatment or a banding treatment that involved adhering a hook-and-loop fastener coated with varying concentrations of indole-3-butyric acid (IBA) around the shoot base to create a localized etiolated zone before taking cuttings. Data on rooting percentage and number of roots per cutting were analyzed using logistic and Quasi-Poisson regression, respectively. Etiolated cuttings treated with a band without IBA had the highest rooting probability and number of roots; however, etiolated cuttings across all banding treatments had similarly successful results. Additionally, there were several significant differences in rooting probabilities and root numbers between banding treatments within the shade- and light-grown groups. This research evaluated asexual propagation approaches for use with northern spicebush and provides a framework for the adoption and development of this taxon as a nursery crop.

Sensing and Automation Technologies for Ornamental Nursery Crop Production: Current Status and Future Prospects.

The ornamental crop industry is an important contributor to the economy in the United States. The industry has been facing challenges due to continuously increasing labor and agricultural input costs. Sensing and automation technologies have been introduced to reduce labor requirements and to ensure efficient management operations. This article reviews current sensing and automation technologies used for ornamental nursery crop production and highlights prospective technologies that can be applied for future applications. Applications of sensors, computer vision, artificial intelligence (AI), machine learning (ML), Internet-of-Things (IoT), and robotic technologies are reviewed. Some advanced technologies, including 3D cameras, enhanced deep learning models, edge computing, radio-frequency identification (RFID), and integrated robotics used for other cropping systems, are also discussed as potential prospects. This review concludes that advanced sensing, AI and robotic technologies are critically needed for the nursery crop industry. Adapting these current and future innovative technologies will benefit growers working towards sustainable ornamental nursery crop production.

Forecasting the potential distribution of invasive leafminer pests, Liriomyza spp. (Diptera: Agromyzidae), and their natural enemies

AbstractThree species of polyphagous Liriomyza leafminers (Diptera: Agromyzidae), Liriomyza huidobrensis, L. sativae, and L. trifolii, are internationally significant pests of vegetable and nursery crops that have each been recently detected on the Australian mainland. Due to the early stages of these invasions in Australia, it is unclear how climatic conditions are likely to support and potentially restrict the distribution of these species as they expand into novel ranges and threaten agricultural production regions. Additionally, it is unclear how natural enemies, particularly parasitoid wasps, will mitigate the impacts of these pests. Here, we predicted the future establishment potential of L. huidobrensis, L. sativae and L. trifolii in Australia, as well as two cosmopolitan parasitoid wasps known to provide control of the flies in both field and glasshouse settings, Diglyphus isaea (Hymenoptera: Eulophidae) and Hemiptarsenus varicornis (Hymenoptera: Eulophidae). Global distribution data spanning 42 countries were compiled and used to validate a process‐based model of establishment potential based on intrinsic population growth rates. The modelling approach successfully captured the international distribution of the three Liriomyza species based on environmental variables and predicted the high suitability of non‐occupied ranges in Australia. The largely unfilled climatic niche available to these pests demonstrates the early stages of their Australian invasions and highlights locations where vegetable production regions are at particular risk. In addition to Australia, our results highlight many regions globally where L. sativae, L. trifolii and L. huidobrensis have the potential to spread in the future. Within Australia, D. isaea and H. varicornis are predicted to have a large spatial and seasonal overlap with each Liriomyza species and thus are expected to influence the future spread of these pests and play an important role in local pest management programs.

Understanding Current Labor Shortage and Mechanization in New Jersey Nursery Crop Operations

We conducted a survey of New Jersey’s nursery industry to understand the current levels of labor shortage, how this has affected specific tasks related to the production capacity of the industry, and the actual level of mechanization. Survey results identified priority areas needing mechanization. There is a need for greater mechanization in almost all areas of nursery production to reduce the reliance on labor and or improve the efficiency of labor. Other Implications related to Extension programming on nursery mechanization are also discussed.

Growth and Quality Response of Four Container-grown Nursery Crop Species to Low-phosphorus Controlled-release Fertilizer

The amount of phosphorus (P) conventionally recommended and applied to container nursery crops commonly exceeds plant requirements, resulting in unused P leaching from containers and potentially contributing to surface water impairment. An experiment was replicated in the Middle Atlantic Coastal Plain (MACP) and Ridge and Valley ecoregions of Virginia to compare the effect of a low-P controlled-release fertilizer (CRF, 0.9% or 1.4% P depending on species) vs. a conventional CRF formulation (control, 1.7% P) on plant shoot growth, crop quality, and substrate nutrient concentrations of four species: ‘Natchez’ crape myrtle (Lagerstroemia indica × Lagerstroemia fauriei), ‘Roblec’ Encore azalea (Rhododendron hybrid), ‘Radrazz’ Knock Out rose (Rosa hybrid), and ‘Green Giant’ arborvitae (Thuja plicata × Thuja standishii). In both ecoregions, the low-P CRF resulted in 9% to 26% lower shoot dry weight in all four species compared with those given the conventional formulation, but quality ratings for two economically important species, ‘Radrazz’ Knock Out rose and ‘Green Giant’ arborvitae, were similar between treatments. When fertilized with the low-P CRF, ‘Roblec’ Encore azalea and ‘Natchez’ crape myrtle in both ecoregions, and ‘Green Giant’ arborvitae in the MACP ecoregion had ∼56% to 75% lower substrate pore-water P concentrations than those that received the control CRF. Nitrate-nitrogen (N) concentrations in substrate pore water at week 5 were more than six times greater in control-fertilized plants than in those that received a low-P CRF, which may have been a result of the greater urea-N content or the heterogeneous nature of the low-P CRFs. Lower water-extractable pore-water P and N indicate less environmental risk and potentially increased crop efficiency. Our results suggest low-P CRFs can be used to produce certain economically important ornamental nursery crops successfully without sacrificing quality; however, early adopters will need to evaluate the effect of low-P CRFs on crop quality of specific species before implementing on a large scale.

Significance to the Horticulture Industry

Significance to the Horticulture Industry

Effect of Irrigation, Fertilizer Rate and Placement, and Two Substrates on Growth of Rose and Hydrangea

Abstract Current best management practices for containerized nursery crops maximize plant growth while minimizing nutrient leaching. This study tested how plant growth was affected by reducing the standard fertilizer rate when grown in two soilless substrates with different physical properties under two irrigation levels. Controlled-release fertilizer (CRF) treatments included 1.0x (45g) applied as topdress (TD), 1.0x (45 g) incorporated throughout (IT), or 0.75x (34 g) incorporated into only the top half (TH) of the container. Rosa ‘BAIneon' Screaming Neon Red™ rose and Hydrangea macrophylla ‘PIIHM-II' Endless Summer® Bloomstruck® hydrangea were potted using Aeration+Potting Mix (AS40) or All-purpose Potting Mix (PM2) substrates. Plants received higher [12.7 mm (0.5 in)] or lower [8.3 mm ( 0.33 in)] irrigation per day for 18 weeks. Final dry weight (DW) was most affected by fertilizer, to a lesser extent substrate, and not at all by irrigation. Regardless of taxa, the largest DWs were produced when plants were grown in PM2 and received nutrients via IT or TD compared to TH. Electrical conductivity was greatest in PM2 substrate with a 1.0x fertilizer rate, regardless if applied IT or TD. Taxa were unsaleable in the TH treatment, thus negating the environmental benefits achieved by reductions in leaching from lower fertilization rates. Species used in this study: ‘Screaming Neon Red™' rose (Rosa ‘BAIneon'); ‘Endless Summer® Bloomstruck®' hydrangea [Hydrangea macrophylla (Thunb.) Ser.]‘PIIHM-II').