Browsing by Author "Owen, James S."

Now showing 1 - 9 of 9
  • Thumbnail Image
    Best Management Practice Use and Efficacy for the Virginia Nursery and Greenhouse Industry
    Mack, Rachel E. (Virginia Tech, 2017-01-24)
    Best management practices (BMPs) are used in the nursery and greenhouse industry to increase production efficiency, and also serve to help meet clean water limitations on contaminants entering waters such as the Chesapeake Bay Watershed. Research is lacking on which BMPs are most widely used or most efficacious for Virginia nursery and greenhouse growers. Objectives of this work were to determine BMP use, barriers to adoption, and scientific efficacy. We conducted a survey of Virginia growers to find the 1) most widely used BMPs, 2) reasons behind BMP use, and 3) any barriers to BMP adoption. Sixty growers (17%) responded to the survey. The most widely used BMPs included irrigation scheduling, integrated pest management, optimized irrigation efficiency, plant need based watering, grouping plants by water needs, on-site water capture and collection, and use of controlled-release fertilizers (CRFs). Cost was a barrier to BMP adoption, and environmental concern was a commonly reported reason for BMP use. We documented the science supporting selected water-related BMPs (grass buffer strips, CRFs, and irrigation optimization BMPs). Providing the science supporting BMP use gives growers confidence in implementing BMPs to limit water contamination, and prevent waste.
  • Thumbnail Image
    Compost Feedstock and Compost Acidification Affect Growth and Mineral Nutrition in Northern Highbush Blueberry
    Costello, Ryan C.; Sullivan, Dan M.; Bryla, David R.; Strik, Bernadine C.; Owen, James S. (2019-06)
    Newmarkets for organic northern highbush blueberry (Vaccinium corymbosum L.) have stimulated interest in using composts specifically tailored to the plant's edaphic requirements. Because composts are typically neutral to alkaline in pH (pH 7 to 8), and blueberry requires acidic soil (pH 4.2 to 5.5), we investigated elemental sulfur (S-0) addition as a methodology for reducing compost pH. The objectives were to 1) characterize initial compost chemistry, including the pH buffering capacity of compost (acidity required to reduce pH to 5.0), 2) measure changes in compost chemistry accompanying acidification, and 3) evaluate plant growth and mineral nutrition of blueberry in soil amended with an untreated or acidified compost. Ten composts prepared from diverse feedstocks were obtained from municipalities and farms. Addition of finely ground S-0 reduced compost pH from 7.2 to 5.3, on average, after 70 d at 22 degrees C, and increased the solubility of nutrients, including K (from 22 to 36 mmol((+))/L), Ca (from 5 to 19 mmol((+))/L), Mg (from 5 to 20 mmol((+))/L), and Na (from 6 to 9 mmol((+))/L). Sulfate-S, a product of S-0 oxidation, also increased from 5 to 45 mmol((-))/L. The composts were incorporated into soil at a high rate (30% v/v) in a greenhouse trial to evaluate their suitability for use in blueberry production. Shoot and root growth were strongly affected by compost chemical characteristics, including pH and electrical conductivity (EC). Potassium in compost was highly variable (2-32 g center dot kg(-1)). Concentration of K in the leaves increased positively in response to compost K, whereas shoot dry weight and root growth declined. Leaf Mg also declined in response to compost K, suggesting that elevated K concentrations in compost may cause Mgdeficiency. Composts with the highestKwere also high in total N, pH, andEC. Compost acidification to pH <= 6 improved growth and increased leafMg concentration. On the basis of these results, composts derived from animal manures or young plant tissues (e.g., green leaves) appear to be unsuitable for high-rate applications to blueberry because they usually require high amounts of S-0 for acidification and are often high in EC and K, whereas those derived from woody materials, such as local yard debris, appear promising based on their C:N ratio, compost acidification requirement, and EC.
  • Thumbnail Image
    A Fine Line between Phytotoxicity and Blue When Producing Hydrangea macrophylla in a Nursery at a Low Substrate pH
    Pietsch, Grace M.; Brindley, Julie C.; Owen, James S.; Fulcher, Amy (MDPI, 2022-07-30)
    Hydrangea macrophylla exhibiting blue sepals (versus purple or pink) have improved marketability; however, little research has been conducted to evaluate aluminum (Al), the element responsible for bluing, on crop growth, effectiveness of bluing sepals, and characteristics of flower clusters in an outdoor nursery. This study compared substrate Al availability, crop growth, flower color, number, and size over a 56-week period in two locations. A polymer coated (90-day release) or ground aluminum sulfate [Al2(SO4)3; water soluble] was either incorporated into a non-limed pine bark substrate, applied to the surface of the substrate as a top dress, or as a routinely applied Al2(SO4)3 drench (low concn.) or applied once (high concn.). In general, application of Al increased plant foliar Al concentration, but also decreased substrate pore-water pH and increased electrical conductivity (EC) with varying effects based on the applied product’s solubility and subsequent longevity. Aluminum sulfate increased the potential of Al phytotoxicity negatively affecting root morphology and creating an undesirable rhizosphere electrochemistry due to the pH being continually acidic, <4, and the EC being temporarily increased to >1.5 mS·cm−1. These suboptimal rhizosphere conditions resulted in a lower quality or smaller plant. No plants exhibited clear, deep blue flower cluster sought by consumers. Neither the effect of pore water pH or EC could, alone or in combination, account for the lack of plant vigor or blue flower clusters when substrate and foliar Al concentrations were adequate in flowering H. macrophylla. More research is needed to investigate the effect of pore-water electrochemical properties, possible mineral nutrient co-factors that provide Al synergisms or toxicity protections, and holistic plant health on ensuring blue coloration of a vigorous H. macrophylla.
  • Thumbnail Image
    Greenhouse and Nursery Water Management Characterization and Research Priorities in the USA
    White, Sarah A.; Owen, James S.; Majsztrik, John C.; Oki, Lorence R.; Fisher, Paul R.; Hall, Charles R.; Lea-Cox, John D.; Fernandez, R. Thomas (MDPI, 2019-11-08)
    Nursery, floriculture, and propagation production accounted for 79% ($13.3 Billion) of 2017 ornamental specialty crop production in the United States. Access to high quality water sources is increasingly limited for irrigating these economically significant crops. Given the production, environmental, and economic issues associated with the use of water—including recycled, reclaimed, surface, and ground water—it is critical to develop sustainable runoff, containment, and remediation technologies, and to identify alternative sources of water. To better understand current practices and future water-related needs as perceived by grower stakeholders, an online survey was distributed nationally and five in-depth round table discussion sessions were conducted at the Mid-Atlantic Nursery Trade Show, Gulf States Horticultural Expo, California Grown Show, AmericanHort’s Cultivate, and the Farwest Show with a total of 36 individual industry participants. A team of research and extension specialists facilitated by a Specialty Crops Research Initiative Planning Grant (NIFA Project # 2011-51181-30633) analyzed and concisely summarized the results from the survey and the round table discussions. Research priorities related to water management identified by stakeholders revolved around six themes: (1) recycled water infrastructure and management; (2) contaminants; (3) plant health and water quality; (4) water treatment technologies; (5) competing and complementary water uses; (6) societal perception of agricultural water use.
  • Thumbnail Image
    Irrigation return flow and nutrient movement mitigation by irrigation method for container plant production
    Abdi, Damon E.; Owen, James S.; Brindley, Julie C.; Birnbaum, Anna; Cregg, Bert M.; Fernandez, R. Thomas (Springer, 2021-09)
    The production of nursery crops demands substantial irrigation, with overhead irrigation the most common method of application; however, this method is inefficient with respect to water used and the precision with which it is applied, resulting in the generation of irrigation return flow and concomitant agrochemical export. Microirrigation systems such as individual container spray stakes provide water directly to crops thus applying water more efficiently than overhead systems but may be more costly in terms of installation (smaller pipes and components; however, a greater quantity of pipes and components) and maintenance. The study was conducted at the Michigan State University Research Nursery, where four ornamental shrub taxa were produced in #3 (11.3 L) containers using a control with 19 mm overhead irrigation per day and a conventional phosphorus fertilizer (Conv) (19-2.16-6.64), compared with four treatments: a static, daily (2 L per container) spray stake irrigation (SS2Lpd) and conventional phosphorus fertilizer; a static daily (2 L per container) spray stake irrigation and low phosphorus fertilizer (LowP) (19-1.62-6.64); spray stake irrigation based on substrate volumetric water content (theta) (up to 2.4 L per container) (SS theta) and conventional fertilizer; and spray stake irrigation based on theta (up to 2.4 L per container) and low phosphorus fertilizer. Spray stakes reduced irrigation by 76-80% compared to the overhead control, and reduced the generation of both surface and subsurface irrigation return flow (IRF), mitigating the movement of both N and P (over 98% reduction in surface IRF). Plant growth index (GI) was measured on 12 June 2017 and 6 October 2017, followed by a destructive harvest to measure shoot dry weight, and shoot nutritional content. For all four taxa, microirrigation systems were capable of producing plants of equivalent GI and shoot nutritional concentration; however, plants receiving the low phosphorus fertilizer produced less shoot biomass. Microirrigation is effective in reducing water use, water lost to IRF (particularly surface IRF), and associated fertilizer movement, while maintaining crop size.
  • Thumbnail Image
    Pre- and Postharvest Practices for Optimizing the Postharvest Quality of Cut Sunflower, Dahlia, and Delphinium
    Peck, Leslie Kathryn (Virginia Tech, 2016-05-27)
    The primary objective of this research was to identify practices by which specialty cut flower growers can extend the vase life of cut delphinium, sunflower, and dahlia. Experiments investigated the effects of nitrogen fertilization rate on delphinium 'Guardian Mix' and the effects of deficit irrigation on delphinium 'Guardian Blue.' 'Guardian Mix' plants produced marketable cut stems at nitrogen rates as low as 50 mg/L. Deficit irrigation did not change vase life, stomatal conductance, or transpiration rates of delphinium 'Guardian Blue.' Studies tested the effects of foliar calcium applications or benzyladenine application on sunflower 'Moulin Rouge' and 'Procut Lemon.' Calcium did not change the vase life, stomatal conductance, or transpiration rates of either sunflower cultivar. Benzyladenine applied as a preharvest spray or a postharvest dip did not alter vase life of sunflower 'Moulin Rouge' or 'Procut Lemon.' Transpiration rate and conductance rates of sunflowers significantly decreased in the first three days after harvest. In both sunflower experiments, vase life of 'Moulin Rouge' was shorter than vase life of 'Procut Lemon.' Benzyladenine was also applied to dahlia 'Park Princess' and 'Karma Yin Yang' cut flowers. Benzyladenine did not change dahlia vase life. Dahlia 'Park Princess,' 'Bride to Be,' 'Cherish,' and 'Lollipop' cut flowers were not sensitive to exogenous ethylene. Further experiments tested the effect of flower stage at harvest, vase water temperature, or preharvest fungicide application on dahlia 'Park Princess' and 'Karma Yin Yang' cut flowers. Vase life of 'Park Princess' flowers was extended when flowers were harvested before fully open, but 'Park Princess' flowers harvested at budbreak failed to open completely after harvest. 'Karma Yin Yang' cut flower vase life did not differ when flowers were harvested at different stages. Placing cut dahlias in hot vase water had varied effects, but did not extend vase life of either cultivar. Fungicide applications extended vase life of 'Park Princess' flowers. However, the use of fungicide is not necessary to prevent postharvest fungal infection in cut dahlias. The results of all experiments indicate that optimal handling practices vary between cut flower taxa and that factors determining cut flower vase life are complex.
  • Thumbnail Image
    Surveying North American Specialty Crop Growers' Current Use of Soilless Substrates and Future Research and Education Needs
    Fields, Jeb S.; Owen, James S.; Lamm, Alexa; Altland, James; Jackson, Brian; Oki, Lorence; Samtani, Jayesh B.; Zheng, Youbin; Criscione, Kristopher S. (MDPI, 2023-08-31)
    Many specialty crop growers are transitioning high-value crops from in-ground production to soilless culture due to the diminishing availability of fumigants, increasing pest pressure, extreme weather, and the need for flexible production practices. The objective of this study was to determine the research and educational needs of specialty crop growers who are transitioning to soilless substrates. North American growers were surveyed using an online instrument that incorporated Likert-type statement matrices, open-ended questions, and demographic questions. Additionally, two virtually led focus groups were conducted to further expand upon the quantitative findings with descriptive data. Respondents indicated the most important factors in considering whether to adopt soilless substrates were improving, managing, and reducing overall plant quality, disease management, and crop loss, respectively. The most important research needs were understanding the effects of substrates on crop quality and uniformity, fertilizer management, and economic costs and benefits/return on investment. In both the grower survey and focus groups, crop quality and uniformity were among the highest-scored responses. Food safety, disease and pest management, consumer perception, substrate disposal-related issues, transportation, and return-on-investment were also identified as important factors when considering soilless substrates.
  • Thumbnail Image
    Water Fluxes in Soil-Pavement Systems: Integrating Trees, Soils and Infrastructure
    de la Mota Daniel, Francisco Javier (Virginia Tech, 2019-01-31)
    In urban areas, trees are often planted in bare soil sidewalk openings (tree pits) which recently are being covered with permeable pavements. Pavements are known to alter soil moisture and temperature, and may have implications for tree growth, root development and depth, drought resilience, and sidewalk lifting. Furthermore, tree pits are often the only unsealed soil surface and are important for water exchange between soil and atmosphere. Therefore, covering tree pits with pavement, even permeable, may have implications for the urban water balance and stormwater management. A better understanding of permeable pavement on tree pavement soil system functioning can inform improved tree pit and street design for greater sustainability of urban environments. We conducted experiments at two sites in Virginia, USA (Mountains and Coastal Plain) with different climate and soil. At each location, we constructed 24 tree pits in a completely randomized experiment with two factors: paved with resin-bound porous-permeable pavement versus unpaved, and planted with Platanus x acerifolia 'Bloodgood' versus unplanted (n = 6). We measured tree stem diameter, root growth and depth, and soil water content and temperature over two growing seasons. We also monitored tree sap flow one week in June 2017 at the Mountains. In addition, we calibrated and validated a soil water flow model, HYDRUS-1D, to predict soil water distribution for different rooting depths, soil textures and pavement thicknesses. Trees in paved tree pits grew larger, with stem diameters 29% (Mountains) and 51% (Coastal Plain) greater. Roots developed faster under pavement, possibly due to the increased soil water content and the extended root growing season (14 more days). Tree transpiration was 33% of unpaved and planted pit water outputs, while it was 64% for paved and planted pits. In June 2016, planted pits had decreased root-zone water storage, while unplanted pits showed increased storage. A water balance of the entire experimental site showed overall decreased soil water storage due to tree water extraction becoming the dominant factor. HYDRUS-1D provided overall best results for model validation at 10 cm depth from soil surface (NSE = 0.447 for planted and paved tree pits), compared to 30- and 60 cm depths. HYDRUS-1D simulations with greater pavement thickness resulted in changes in predicted soil water content at the Coastal Plain, with higher values at 10- and 30-cm depths, but lower values at 60-cm depth. At the Mountains, virtually no difference was observed, possibly due to different soil texture (sandy vs clayey). Tree pits with permeable pavement accelerated tree establishment, but promoted shallower roots, possibly increasing root-pavement conflicts and tree drought susceptibility. Paved tree pits resulted in larger trees, increasing tree transpiration, but reduced soil evaporation compared to unpaved pits. Larger bare soil pits surrounded by permeable pavement might yield the best results to improve urban stormwater retention. Also, HYDRUS 1D was successful at simulating soil water content at 10-cm depth and may be valuable to inform streetscape design and planning.
  • Thumbnail Image
    Watson on the Farm: Using Cloud-Based Artificial Intelligence to Identify Early Indicators of Water Stress
    Freeman, Daniel; Gupta, Shaurya; Smith, D. Hudson; Maja, Joe Mari; Robbins, James; Owen, James S.; Peña, Jose M.; de Castro, Ana I. (MDPI, 2019-11-13)
    As demand for freshwater increases while supply remains stagnant, the critical need for sustainable water use in agriculture has led the EPA Strategic Plan to call for new technologies that can optimize water allocation in real-time. This work assesses the use of cloud-based artificial intelligence to detect early indicators of water stress across six container-grown ornamental shrub species. Near-infrared images were previously collected with modified Canon and MAPIR Survey II cameras deployed via a small unmanned aircraft system (sUAS) at an altitude of 30 meters. Cropped images of plants in no, low-, and high-water stress conditions were split into four-fold cross-validation sets and used to train models through IBM Watson’s Visual Recognition service. Despite constraints such as small sample size (36 plants, 150 images) and low image resolution (150 pixels by 150 pixels per plant), Watson generated models were able to detect indicators of stress after 48 hours of water deprivation with a significant to marginally significant degree of separation in four out of five species tested (p < 0.10). Two models were also able to detect indicators of water stress after only 24 hours, with models trained on images of as few as eight water-stressed Buddleia plants achieving an average area under the curve (AUC) of 0.9884 across four folds. Ease of pre-processing, minimal amount of training data required, and outsourced computation make cloud-based artificial intelligence services such as IBM Watson Visual Recognition an attractive tool for agriculture analytics. Cloud-based artificial intelligence can be combined with technologies such as sUAS and spectral imaging to help crop producers identify deficient irrigation strategies and intervene before crop value is diminished. When brought to scale, frameworks such as these can drive responsive irrigation systems that monitor crop status in real-time and maximize sustainable water use.