Browsing by Author "Uchanski, Mark, advisor"

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Open Access
An evaluation of yield and quality characteristics for vegetable crops grown under organic management in Fort Collins, Colorado
(Colorado State University. Libraries, 2020) Mason, Tyler, author; Uchanski, Mark, advisor; Bartolo, Michael, committee member; Johnson, Sarah, committee member; Prenni, Jessica, committee member
To view the abstract, please see the full text of the document.
Open Access
Evaluation of bactericides and plant defense inducers in the presence and absence of onion pathogens Pantoea spp. and Burkholderia gladioli in Colorado
(Colorado State University. Libraries, 2022) Machado Burke, Antoinette, author; Uchanski, Mark, advisor; Bartolo, Michael, committee member; Lang, Jillian, committee member
Bacterial diseases can cause significant annual crop losses if left untreated. U.S. onion growers combat bacterial disease pressure through a variety of management practices, including crop rotation, irrigation management, and proper cold storage postharvest. In 2019, twelve national research institutions formed a collaborative project called "Stop the Rot" (StR) to develop diagnostic identification tools and research cultural practices across different onion growing regions to mitigate onion bacterial rots. As part of that effort, CSU researchers conducted two years of field trials in 2020 and 2021 to compare the efficacy of commercially available bactericides to prevent bacterial rot on three different onion cultivars (Avalon, Snowball, Vaquero). Artificial bacterial inoculation was prepared using Pantoea spp. and Burkholderia gladioli isolates. The pesticide products included the following types: traditional copper bactericides (Kocide and ManKocide), sanitizers (Oxidate 5.0), biological microorganisms (BlightBan A506), and plant defense inducing productions (Actigard and Lifegard). At harvest in year one, the incidence of bacterial rot was not significantly impacted by bactericide treatment since rot was not present in 2020. In 2021, for 'Vaquero' onion, the Kocide treatment had significantly more rot compared to other treatments and the control after cold storage. For 'Snowball', the BlightBanA506 treatment had a significantly- higher rot percentage than the ManKocide treatment. These results will help Colorado onion growers accurately assess production risks and select bactericides that meet their needs on the farm. Ongoing research on bactericide efficacy, combined with collaborative results from colleagues in Georgia, New York, Utah, and Washington, will help domestic producers "stop the rot" in their onion crops.
Open Access
Fruit cluster pruning impacts on yield and quality of three tomato cultivars in an organic high tunnel system
(Colorado State University. Libraries, 2018) Mitchell, Brian Anthony, author; Uchanski, Mark, advisor; Bartolo, Michael, committee member; Elliott, Adriane, committee member
The successful production of high-quality, high-yielding crops is important for fruit and vegetable producers, especially growers who use high tunnels. The valuable space within a high tunnel is well-suited to organic farming and can be used to grow many specialty crops. Fruit load management is practiced in tree fruit production (e.g. apples and peaches), but there is little consensus concerning the effectiveness of fruit cluster pruning on tomato (Solanum lycopersicum) when considering its impact on fruit yield, quality, and marketability. There is also no published research on tomato cluster pruning in certified organic systems or intensively-managed high tunnels (e.g. densely-planted, trellised, vegetatively pruned plants) on the Front Range of Colorado. The objective of this research was to address and add to the present knowledge of production techniques for cultivating indeterminate tomatoes in a high tunnel under intensive organic management. In 2016 and 2017, a randomized complete block design was used to test the effects of cluster pruning within a high tunnel on certified organic land at Colorado State University's Agricultural Research, Development, and Education Center, South (ARDEC S.). Two treatments and three cultivars of tomato were selected for the study; the treatment-cultivar combinations were replicated six times within a high tunnel. The treatments involved reducing fruit loads to three fruits and six fruits per cluster while plants with unpruned clusters, which developed up to ten fruits naturally, served as the control. Tomato cultivars evaluated were 'Cherokee Purple', a widely-studied heirloom, and two hybrids: 'Jet Star' and 'Lola'. Parameters measured included total yield, individual fresh fruit weight, soluble solids content, marketable yield, and non-marketable yield. Averaged over two growing seasons, individual fresh fruit weight increased for both hybrids in the three-fruit treatment, but 'Cherokee Purple' did not respond to the cluster pruning treatments. There was no decrease in total yield between treatments and the unpruned control; however, cultivars performed differently with 'Jet Star' yielding more than the other two cultivars. In a complete analysis, soluble solids content and marketability measurements were more influenced by cultivar than cluster pruning treatments: 'Jet Star' had the highest marketable yields of all cultivars tested, while 'Cherokee Purple' produced larger non-marketable yields. In summary, cluster pruning produced larger organic tomatoes without reducing yield or quality for two of the three cultivars used in the study. Cultivar selection remains one of the largest factors in determining yield, quality, and marketability of a crop.
Open Access
Impacts of black soldier fly larval frass on vegetable crop production
(Colorado State University. Libraries, 2023) Chavez, Maria, author; Uchanski, Mark, advisor; Davis, Jessica, committee member; Tomberlin, Jeff, committee member; Ode, Paul, committee member
The "insects as food and feed" movement is gaining considerable momentum as a novel way to provide protein to human and animal diets. Insects require significantly fewer resources, such as water and land, to produce, process and distribute as a food source. Food, service, and restaurant partners often donate their waste to insect producers. This converts landfill destined waste into high protein food sources. The left-over waste product from mass rearing insects, known as frass, creates a problem for insect producers. However, across the food system numerous industries are involved, and this research examines how waste from the hospitality and insect industries can be utilized in vegetable crop production. Peat is the most common medium for plant growth in greenhouse and gardening operations; however, peat extraction has severe environmental consequences for marsh ecosystems, surrounding environments, and climate change. Partially replacing peat with insect frass could reduce industrial waste from insect and food producers and decrease peat consumption. Greenhouse studies were designed to investigate the use of frass in vegetable production. In pot studies with arugula, lettuce, and tomato different ratios of peat and vermicompost and peat and insect frass were compared to a 100% peat control. Arugula and lettuce grown in distillery grain frass, all BSFL treatments were equal or better in yield than the 100% peat control, regardless of season. For brewery grain frass, most treatments in arugula and lettuce were worse or comparable to the peat control in yield, regardless of season. The diet of the larvae (distillery grain vs. brewery grain) was a significant factor in determining the impacts on vegetable yield. Arugula and lettuce leaf tissues were analyzed for nutrient concentrations. Primary macronutrient (NPK) concentrations were higher in frass treatments for both crops. Secondary macronutrients and micronutrients did not show clear trends on the effect of distillery or brewery grain frass. Tomatoes did not produce any significant differences across insect frass treatments, though average individual fruit weight was significantly higher in low percentages of vermicompost. Emergence, germination, and seedling vigor of arugula, lettuce, and tomato seeds were negatively impacted by brewery grain frass in the absence of vermicompost. In the presence of vermicompost, low concentrations of insect frass in a germination mixture produced comparable results to a 100% peat control. There are many components of insect frass yet to be fully explored, such as the impact on cation exchange capacity and microbial activity. More research to understand the physical, chemical, and microbial components of the medium will be essential in pushing the field forward, improving the material as an amendment, and closing gaps in the cycle of production.
Open Access
Impacts of LED interlighting on the growth, yield, and quality of hydroponic greenhouse tomatoes
(Colorado State University. Libraries, 2018) Burns, Tara Nicole, author; Uchanski, Mark, advisor; Pilon-Smits, Elizabeth, committee member; Newman, Steven, committee member
Recent technological advances have lead to light emitting diode (LED) lights becoming more readily available. They are becoming established as a way to supplement light in controlled environment crop production and are typically used as a top light. Due to their unique characteristics, LED lighting infrastructure and the lights themselves can also be placed within the canopy (interlighting bars); a location that has typically been hard to reach with traditional high-pressure sodium or ceramic discharge lamps. Currently, there is little research on the overall effects of interlighting on plant growth and productivity. Therefore, four studies were conducted to measure the impacts of interlighting on the growth of hydroponically grown greenhouse tomatoes. Interlighting was evaluated for a 16:8 photoperiod (light:dark) under both naturally increasing and decreasing daylengths. Tomato plants were grown in perlite and trained to a single leader on an overhead support system. Flowers were hand pollinated twice a week to ensure fruit set. Data collected included vegetative biomass, individual fruit weight, total fruit yield, soluble solids content, pH, and leaf gas exchange to assess tomato vegetative and reproductive growth and physiological parameters. In addition, the photosynthetically active radiation (PAR) output of the interlighting was measured to create a light distribution map. Lastly, a distance experiment was conducted to measure the effects of the proximity of the interlighting bars on early tomato vegetative growth. Across three experiments we observed that interlighting significantly increased gas exchange measurements (i.e. photosynthetic rate) in individual lighted leaves, however, overall vegetative growth and fruit yield did not increase. Although individual leaves responded to the additional light resource located in the canopy, it did not significantly increase overall yield on quality of greenhousegrown tomato fruits.
Open Access
Plant growth under photovoltaic arrays of varying transparencies – a study of plant response to light and shadow in agrivoltaic systems
(Colorado State University. Libraries, 2023) Hickey, Thomas, author; Bousselot, Jennifer, advisor; Uchanski, Mark, advisor; Harrow, Del, committee member
Amidst the rising global pressures put on the interdependent systems in the food, energy, and water nexus, this document highlights the potential for systems-based solutions at the intersection of food cultivation, ecosystem services, and energy production in urban and rural environments. Agrivoltaics (APV) is a land-use model that enables simultaneous cultivation of food crops and electricity generation on the same plot of land. Agrivoltaic systems integrate solar photovoltaic (PV) energy generation with agricultural operations, maximizing the utilization of solar energy. This approach has gained significant research interest in the United States with scalable implementation is on the horizon. Research efforts at Colorado State University (CSU) aim to advance the understanding of plant responses to various shade conditions under PV arrays, benefiting stakeholders in agriculture, solar energy industries, policymakers, and governmental agencies. In particular, agrivoltaic research conducted at CSU's Horticulture and Landscape Architecture (HLA) department has focused on open field specialty crops and native pollinator plant species while documenting the overarching light and temperature growing environment. A replicated 2-year crop trial was conducted at the open field test site, comparing crop yield and growing conditions under three different PV module types with varying transparencies to traditional full sun production. Statistical analysis revealed a reduction in squash yield directly under the PV panels while no significant differences in yield for bell peppers, jalapeno peppers, lettuce and tomatoes growing north and south of the arrays. In a separate study, a simulated green roof structure was constructed around an existing PV array at CSU's Foothills Campus to explore the feasibility of rooftop agrivoltaics. A one-year study of six native pollinator plant species was conducted to assess differences in establishment, survivability, growth index, and growing conditions between full sun and PV shade environments. Overall, there were no statistically significant differences in mean Plant Growth Index (PGI) throughout the establishment season, however, notable variations in overwinter survivability were observed. In both studies the PV modules moderated the environment, resulting in lower maximum daytime ambient temperatures and even greater reduction in soil temperature throughout the growing season. Light levels are reduced under all PV module types with the least reduction under semi-transparent modules. Variations in growing conditions in these APV systems indicate the need for further research to optimize PV systems in order to maximize energy production and plant vitality.
Open Access
Supplemental light-emitting diode effects on the growth, fruit quality, and yield of two greenhouse-grown strawberry (Fragaria X ananassa) cultivars
(Colorado State University. Libraries, 2018) Stuemky, Andrea, author; Uchanski, Mark, advisor; Newman, Steve, committee member; Thilmany, Dawn, committee member
Recent interest in off-season, greenhouse-grown food crops using supplemental top lighting(STL) has created opportunities for controlled environmental agriculture (CEA) production of high-value fruit crops such as strawberries (Fragaria X ananassa). Light-emitting diodes (LEDs)can be tailored to specific wavelengths to promote increased production and quality of greenhouse grown crops when used as STL. However, more research is needed to evaluate specific wavelengths of light that can promote increased strawberry fruit production and overall fruit quality in a greenhouse environment. The objectives of this study were to evaluate the effects of three LED STL bars on off-season CEA production of two day-neutral strawberry cultivars, 'Albion' and 'San Andreas'. LED effects on overall vegetative biomass (e.g. stolon production, crown numbers, and leaf area), marketable fruit yield, and fruit quality (e.g. individual fruit weight and soluble solids content (SSC)) were measured during decreasing day lengths of Oct. - Dec.2017 (Exp. 1) and the increasing day lengths of Jan. - April 2018 (Exp. 2). We hypothesized that the addition of STL via three LED bars would increase most measured parameters. Specifically, it was expected that the LED bars with higher densities of blue and red light would produce higher yields and also increase soluble solids content of the berries. The hypotheses were tested by evaluating three LED light top bars (WFR = white far-red, HB = high blue, and LB = low blue) with peaks of blue (450 nm) and red light (665 nm), but at differing photon flux densities (PFD). In these experiments, individual strawberry fruit size and SSC were increased with the use of HB and LB LEDs during the shortening days of Exp. 1. Increased leaf area and crown numbers were also positively affected within all LED treatments (WFR, LB, HB) for 'San Andreas'. The lengthening days of Exp. 2 elicited limited fruiting responses, but stolon production increased within all treatments. In some cases, the two cultivars responded differently to LED STL treatments for leaf area and SSC: 'San Andreas' produced larger leaves and 'Albion' berries having higher SSC than 'San Andreas'. Individual fruit weight of both cultivars increased fruit size in LB and HB treatments in both Exp. 1 and Exp. 2. Our studies indicate that the addition of STL, improved overall strawberry fruit quality and plant growth during shortening day lengths in a greenhouse.
Open Access
The relationship between greenhouse and field performance of diverse cultivars of summer squash and watermelon grown under moisture stressed conditions
(Colorado State University. Libraries, 2019) Ray, Deborah Kay, author; Uchanski, Mark, advisor; Qian, Yaling, committee member; Byrne, Patrick, committee member
Drought stress poses a major threat to the global food supply, and most domestic vegetable growers lack cultivar-specific information that would allow them to adopt best management practices to limit the impacts of these stressors. Summer squash (Cucurbita pepo) and watermelon (Citrullus lanatus) are two crops in the Cucurbitaceae family that are commonly grown and consumed in the U.S. Heirlooms and modern cultivars of these crops with reports of "drought resistance" are currently available on the market without concomitant recommended modifications to irrigation management. Many published greenhouse experiments have been used to screen cultivars and breeding lines for drought resistance, but often lack paired field trials to confirm results. We conducted a greenhouse dry-down study on nine summer squash and 10 watermelon cultivars, and sustained deficit irrigation (SDI) field trials on a selected 13. Our objective was to determine if crop characteristics identified in the greenhouse studies could be predictive of season-long field success under drought conditions. Colorado-bred conventional hybrids were used as control cultivars in both studies, and were hypothesized to have a more drought-sensitive response than cultivars with reports of drought resistance. Parameters evaluated in the greenhouse study included: days to death, percent soil moisture at death, root:shoot ratio, and root system characteristics. The cultivars that were then evaluated in the field study received one of three sustained deficit irrigation treatments: control, deficit, or drought, using a drip irrigation system in a split-plot design with three replications. Control treatments were reduced to approximately half the average recommended number of acre-inches of water per season for each crop, averaging 5.9 and 4.8 inches for summer squash and watermelon, respectively. Deficit and drought irrigation treatments were reduced 50% beyond the control during the treatment interval, which began after flowering and extended over the course of 12 weeks for the squash, and six weeks for watermelon. The deficit treatment plots received irrigations of equal frequency to the control, in half the amount, and the drought treatment plots received irrigations at half the frequency of the control, with the same volume of water as the control applied at each irrigation event. Squash were grown under rain exclusion and watermelons were grown in an open field with rainfall amounts factored into total water application calculations. Soil moisture and environmental conditions were monitored, and yield and quality measures were taken in both crops. Photosynthetic activity was also evaluated twice each season in the summer squash plot using a MultispeQ. Our results revealed that greenhouse performance was often not indicative of field performance, and that almost all squash cultivars produced acceptable levels of marketable yield under severe water deficits in the field. Watermelon cultivars produced marketable fruits in both years, but performance was inconsistent from year to year, and yield was low across all cultivars and treatments. Modern cultivars and heirlooms with reports of drought resistance, such as 'Desert King' watermelon and 'Desert F1' zucchini, did not necessarily out-perform hybrids or open-pollinated cultivars without such reports, such as 'Amiga' watermelon, and 'Jasper' and 'Dark Star' summer squash. By imposing a sustained deficit of more than 50% below recommended season-long rates, we identified five best-performing cultivars of summer squash that experience an approximate yield penalty of 30% under these conditions. The results of this study offer a prescriptive weekly method of irrigation management combined with recommendations for currently available cultivars that can be readily adopted by local, fresh-market growers to enable significant water savings without reductions in quality.