Final report for OW19-346
Project Information
Title: Promoting crop diversification and soil health for cut flower production
Summary: Growing cut flowers as a high-value crop has become popular across Utah in the last five years because of the crop’s unmatched profitability and small space requirements. Yet to date, minimal research and cultivation information exist for Utah, which has resulted in grower adoption of out-of-state materials that are not appropriate for Utah soils or climate conditions. Over-application of fertilizer and use of unsuitable soil amendments have introduced soil health, long-term productivity, and environmental sustainability risks. Therefore, the goal of this project is to answer the following research questions by testing a premium cut flower, Dahlia ‘Café au Lait’:
- What nitrogen rates are needed to maximize economic return on yields (stem length, bloom diameter, and total number of blooms per plant) without buildup of nutrients and salts that negatively affect soil heath, productivity, and environmental sustainability?
- What are current management practices and market prices being used by cut flower farmers in Utah?
- How do native soil conditions and climate impact nutrient management and subsequent yields?
This project will establish Dahlia trials at the Utah Agriculture Experimental Station – Greenville in North Logan, UT, to test and develop in-state nutrient management plans. Participatory research will also be conducted with growers to document present management practices, subsequent soil test results, yield, and profitability data on ranging soil types and climates in the state. Multiple Extension education outreach activities will be organized through conference presentations, field days, farm tours, and a grower association. Social media and digital resources will be developed to produce accessible in-state references on cultivation and soil health. Creating Utah-specific resources for cut flower cultivation that highlight soil health promotes innovative markets for growers by increasing resource use efficiency, yields, and environmental sustainability.
- Develop nutrient rate recommendations for Dahlia cultivation through research trials with five nitrogen rates and data that include soil test results (nitrogen, phosphorus, potassium, pH, and salinity) and yield (date of first harvestable bloom, stem length, bloom diameter, and total number of blooms per plant) over three growing seasons (2019 to 2021).
- Determine baseline production and profitability of Dahlia through a three-year on-farm study of soil test and yield data from six participatory farms (2019 to 2021). The growers span a 200-mile transect in Utah that represents the diverse soil types and ranging climatic conditions, where the majority of the state’s population resides and manages land (the Wasatch Front).
- Raise soil health awareness through in-person outreach events (presentations and field days with needs assessments) and social media documentation of field work that includes live Q&A with the project director.
- Produce clear, specific, and publicly available in-state recommendations for Dahlia cultivation to provide a reference for current and future growers, and responsible hobbyists. These Utah-specific grower guides (Fact sheets, bulletins, and video) will be available in 2022.
Please see the Gantt Chart (Figure-4-Timeline).
Objective 1 Timeline: Establish USU’s Dahlia ‘Café au Lait’ trials in May 2019 and complete first growing season in September 2019. Analyze first year data during Winter 2019-2020. Repeat trials during May – September 2020 and 2021, and analyze the three-year dataset to finalize recommendations in 2021-2022. ** Note, a third year (2021 growing season) was approved as a no-cost extension. This was needed due to the presence of disease pressure in earlier years.
Objective 2 Timeline: Establish Dahlia ‘Café au Lait’ trials on six participatory farms in May 2019 and complete first growing season in September 2019. Analyze management and soil test data during Winter 2019-2020 to provide one-on-one training in fertility management in Spring 2020 and Spring 2021. Complete the second and third field seasons during May – September 2020 and 2021 and analyze the three-year dataset to refine recommendations in 2021-2022. **Note, a third year (2021 growing season) was approved as a no-cost extension because of disease incidence in plant stock. All six producer wanted to participate in 2021, though one moved mid-season, for a total of five datasets from 2021.
Objective 3 Timeline: The Utah Urban and Small Farms Conference takes place each February (2019-2021). 2019 and 2020 Field Days will take place each May and Farm Tours will take place each August. During these outreach events, the Utah Cut Flower Growers Association will meet. Video will be recorded during field activities that fall within Objective 1 timeframes. FacebookLive will take place in 2020. **Note, COVID-19 interrupted in-person programming. Instead of a field day in 2020, we hosted a field day in 2022, as well as presented the dahlia research at the 2022 Urban and Small Farms Conference.
Objective 4 Timeline: Begin data analysis in 2019, finalize data analysis in 2021-2022, and disseminate guides by 2022. **Note, a third year (2021 growing season) was approved as a no-cost extension, thus delaying dissemination of final results to 2022.
Cooperators
- - Producer
- - Technical Advisor
- - Technical Advisor
- - Producer
- - Producer
- - Producer
- - Technical Advisor
- - Producer
- - Producer
Research
Objective 1: Develop nutrient rate recommendations for Dahlia cultivation through research trials over two growing seasons (note: updated to three growing seasons because of variability from unanticipated disease pressure).
Dahlia ‘Café au Lait’ was established in May 2019 at the Utah State University Agriculture Experimental Station – Greenville (UAES) in North Logan, UT. Five nitrogen rates were tested during 2019, 2020, and 2021 growing seasons: 0 (control), 56, 112, 168, and 224 kg Nitrogen ha-1. Each rate was replicated six times with seven plants per replicate, per statistical consultation. Soil was sampled in each plot prior to planting (April) and again in the fall after frost-kill (October). Soil tests included: pH, salinity, phosphorus, potassium, nitrate-nitrogen, and total carbon. Tissue samples were collected in 2021 to assess nitrogen uptake, similar to Ahmad et al. (2012). During the growing season, yield data (plant emergence, date of first cuttable stem, total number of stems per plant, bloom diameter, and plant height) were collected. Soil tests, application rates, and yield were analyzed to determine nutrient management recommendations for Utah soils. To account for environmental variability during each growing season, a weather station recorded atmospheric conditions and automated sensors measured soil moisture of the root zone. Tuberous roots of the dahlias were dug in the fall, but new stock was acquired each spring to reduce virus incidence and buildup.
Though preliminary soil fertility recommendations were expected from the 2019 growing season, virus pressure confounded nutrient rates, thus 2020 and 2021 were needed to develop recommendations, as well as partnership with USU's plant pathology program. In 2021, we also began a partnership with Syngenta, which is the only company producing certified virus-free 'Cafe au Lait' dahlia. Though virus pressure was reduced in 2020 compared to 2019, 2021 provided the most robust results for recommendations to be developed. Melanie Stock oversaw the field trials and data analysis. Dan Drost, Brent Black, and Larry Rupp consulted as needed, and introduced Dr. Stock to Dr. Nischwitz, USU's Plant Pathologist. Note: Because of strong, and unexpected virus pressure with dahlia, the timeline was modified. In the first year, we purchased cuttings from a small farm. Unbeknownst to us, they were infected with several viruses that changed plant behavior and resulted in high mortality rates. In the second year, we sourced industry-standard tubers. According to large-scale companies for ornamental stock, fields are scouted and those with visual virus symptoms are culled, but no virus testing is conducted. We discovered significant virus incidence in this stock as well. Therefore, in our third year (as a result of the no-cost extension and a new industry connection), we were able to source virus-free stock as cuttings. The third year of data was the basis for our recommendations because of strong plant production and lack of confounding behavior.
Objective 2: Determine baseline production and profitability of Dahlia through a two-year on-farm study with six participatory growers.
Each producer received 10 Dahlia ‘Café au Lait’ to grow on their farms (Figure-1-Location-Map). To minimize untargeted variables, the following directions were given: Dahlia must be spaced 61-cm apart and receive at least six hours of sunlight (USDA, 1977). Utah State University (USU) will soil and tissue sample, as in UAES trials (note: this was updated during Covid-19 such that the producers were given instructions to sample their fields and sent postage to mail samples to USU, as trips were restricted). During 2019, growers cultivated Dahlia according to their standard practices. Yield (plant emergence, date of first cuttable flower, stem length, bloom diameter, and total number of stems per plant) and management activities (fertilizer application, tillage, staking, pruning, etc) were recorded on data sheets (Figure-2-Record-Sheet-for-Growers). Prior to planting in 2020 and 2022, USU provided interpretation on their soil test results, explained soil health and sustainability needs with nutrient management, and provided nutrient management plans for 2020 and 2021. Growers were to follow USU guidelines and record the same data as in 2019. Note: We extended the study into 2021. Growers received consultation in 2020 and 2021.
Soil type, nutrient status, climate, and yield will be analyzed for Dahlia across the six farms to evaluate and refine UAES fertilizer rates. Melanie Stock will oversee the on-farm research and data analysis.
Objective 3: Raise soil health awareness through in-person outreach events and social media.
Project data was incorporated into organized outreach events. One session for cut flower production at the Utah Urban and Small Farms Conference, one USU-hosted field day, and one grower-hosted farm tour were to be organized by Melanie Stock each year. She and her graduate student presented on the research data generated by this SARE project. Melanie Stock also co-established the Utah Cut Flower Growers Association to facilitate regular meetings, networking, and communication. Dan Drost, Brent Black, and Larry Rupp presented on relevant topics to the farmers (high tunnel production, irrigation, shading, and greenhouse management) at the conferences and field days. Needs assessments were conducted after each presentation (Figure-3-Needs-Assessment).
Originally, video was to be recorded on project implementation, data collection, and general field activities to post on Facebook and then into a full-length FacebookLive presentation that would also be stored on the Production Horticulture Website as a digital resource (http://extension.usu.edu/productionhort/) with engagement data recorded, such as the number of likes, comments, views, and downloads. Melanie Stock oversaw online media activities. As technology is changing rapidly, needs assessments were conducted after this grant proposal was submitted and the following findings were most specific to Utah flower farmers:
1) Use Instagram (58% preference) instead of Facebook (33% preference), which was considered outdated, or Twitter (6%), which was considered too limiting to share useful information by growers. Therefore, a picture-based format with informative captions optimized information sharing (e.g., research events, news, and updates) for this targeted audience.
2) The USU Production Horticulture (flowers.usu.edu) website was useful for posting fact sheets and growers turned to this site for guides. However, the platform was limiting for content types, as well as limiting in search functions for finding relevant multi-disciplinary content. Therefore, Dr. Stock created a lab website tailored for cut flower growers and research (smallfarmslab.com) to post more diverse content and interface more effectively with Instagram. This also helped us incrementally update growers on our research news.
3) USU Extension's YouTube channel (https://www.youtube.com/channel/UC3UzpQYVg7K7FfLXCi19Gdw) has a strong subscriber list, thus was most effective for posting video recordings, such as those from webinars.
4) With the creation of the Utah Cut Flower Farm Association, we began monthly webinars on Zoom ("Bloomin' Zooms) for members, which was another avenue for presenting information to growers and more embraced than FaceBook Live.
Objective 4: Produce Utah-specific grower guides available by 2022.
Our objective was to publish one Extension Fact Sheet on dahlia cultivation for Utah, explaining soil health and nutrient recommendations with step-by-step calculations for sustainable fertilizer application with corresponding video footage. An Extension Bulletin was aimed to cover 1) the nitrogen rate study and 2) grower trials and perceptions. Melanie Stock oversaw these publications and Dan Drost, Brent Black, and Larry Rupp served as coauthors where appropriate. As the dahlia research initiated our outreach with growers, we realized the need for more media; one fact sheet would be too long and complex and that multiple fact sheets and videos together would help split and organize the information and share it in a more approachable way. As a result, we created:
- A peer-reviewed fact sheet dedicated to sustainable compost and manure application for small farms (published in 2019). This outlines evaluating sources and calculating amounts for small farms (complete with an Excel spreadsheet for calculations). This was a result of finding the severe overuse of these soil amendments by working with farmers through Western SARE. This PDF (https://digitalcommons.usu.edu/extension_curall/2047/) was downloaded 2,085 times, as of October 2022. USU Extension then also added this fact sheet as an HTML website page: https://extension.usu.edu/yardandgarden/research/sustainable-manure-and-compost-application for additional accessibility and searchability.
- A peer-reviewed fact sheet on how to soil sample, select tests, interpret nutrient recommendations, and calculate rates for urban microfarms and gardens (published in 2020). This was created after realizing the complexity of small farms and diverse land management within one farm and need to teach growers how to appropriately sample on small scales (other guides target large-scale farms). This PDF (https://digitalcommons.usu.edu/extension_curall/2116/) was downloaded 641 times, as of Oct 2022.
- A peer-reviewed fact sheet on dahlia mosaic virus is accepted and in press. This details visual symptoms to identify in scouting plants, and best management practices for production. A version of this fact sheet that was not peer-reviewed can be found here: https://extension.usu.edu/pests/research/dahlia-mosaic-virus-1.
- A peer-reviewed production guide for dahlia is in review. An enterprise budget on the profitability of dahlia is in preparation, to be submitted for review in Dec 2022.
- A recorded webinar on dahlia production, with a focus on nutrient management, is on YouTube, which helps explain nutrient needs and the soil sustainability challenges on cut flower farms: https://www.youtube.com/watch?v=akrSA7q5S9I
On-farm trial
The original objective of this study was to work directly with growers to assess productivity and profitability of dahlia, as well as to raise soil health awareness. The results of this study critically highlighted the importance of sustainable soil management outreach for small farms. In tracking key soil indicators for management, all farms had high to excessively high soil test phosphorus (P) (Figure 1). On average, soil test P was three to four times greater than the maximum optimal rate for general crop production. Soil test potassium (K) followed a similar trend (Figure 1), with average soil test K two times greater than the maximum optimal rate for general crop production. While soil test nitrogen (N) is not routinely tested to base nutrient application rates (i.e. management programs typically recommend blanket N application rates based on crop demand assumptions, not testing), results from this trial suggest intermittent nitrogen testing may be important for small farm systems to “check in” that soil test values are not becoming excessive (Figure 1). Moreover, regional recommendations for soil-based nitrogen lack specificity, as the general recommendation only describes maintaining 25 ppm or more when the nitrate-N soil test is conducted (Cardon et al., 2008). Therefore, no upper limit has been established. In the on-farm trial, soil nitrate-N levels were up to four times greater than this recommendation (SARE 2022 FINAL Report figures: Figure 1). Together, these results indicate small farms overapply nutrients, soil fertility management training that is specific to small farms is needed, there is value in including soil nitrate-N testing, and determining upper thresholds of soil test N is needed for additional management guidance.
The soil test results for macronutrients did not significantly decrease over the course of the study, which provided insight into strongly held values by cut flower farmers that will be important to incorporate into future Cooperative Extension programming, as well as the long term challenge of reducing levels once they become excessive. The use of compost and “natural” products were emphasized by most growers and incorporated every year. Though compost adds organic matter that is needed in Utah soils, compost also supplies high amounts of P and K, which led to excessive soil nutrient levels, as well as elevated salinity that can reduce yield. Soil salinity averaged around 2 dS m-1 for growers in this study (SARE 2022 FINAL Report figures: Figure 1), which is the threshold for soil test laboratories to flag soil as “high” for most horticultural crops. Though research is needed to establish incremental yield decline by soil salinity level with dahlia, 1.1 dS m-1 is considered to be the threshold for irrigation water for dahlia, highlighting the intolerance of dahlia to elevated salinity (Australian Water Quality Center, 2022). Nutrient loading and subsequently elevated soil salinity help explain the low and declining yields reported by growers, who averaged 1.5 marketable stems per plant in 2019 (±0.7), 1.5 marketable stems per plant in 2020 (±0.90), and 0.4 marketable stems in 2021 (±0.2).
For consultations and outreach, growers were asked to document management. In 2019, only documentation was requested. In 2020, amidst the pandemic, email and phone conversations were conducted to recommend soil management approaches based on test results. In 2021, soil test reports were aggregated with recommendations. Creating visually appealing data tables and typing out recommendations as a one- to two-page handout that was delivered to each farm, appeared to be most successful in helping to convey needed management changes for dahlia. Having paper copies of yearly soil test results together on one page, with a simple, yet farm-specific and detailed, interpretation resonated with growers and will be incorporated into future outreach.
Research farm trial
In establishing nutrient recommendations for dahlia through a variable N-rate trial at the Utah Agricultural Experiment Station – Greenville Research Farm, data in 2021 were most promising. Virus incidence resulted in plant mortality or severe symptoms in 49% of plants in 2019 and 46% of plants in 2020, which added variability to the N-response data in these years (SARE 2022 FINAL Report figures: Figure 2). In 2021, certified virus-free stock were sourced through a new industry collaboration. Though 6% of 2021 plants tested positive for two virus strains, symptoms were not severe and no plants died. As a result, total yield and marketability was greatest in 2021 and trended with N application rates (SARE 2022 FINAL Report figures: Figure 2). Both 168 and 224 kg N per ha-1 resulted in the greatest total yield of 9.3 (±0.7 SE) and 9.7 (±0.6 SE) stems per plant, respectively (SARE 2022 FINAL Report figures: Figure 2). The marketable yields were 6.6 (±1.3 SE) and 6.6 (±0.3 SE) stems per plant for 168 and 224 kg N per ha-1 rates, respectively (SARE 2022 FINAL Report figures: Figure 2). With these yields, soil test values remained low (SARE 2022 FINAL Report figures: Figure 3). Application of P and K were determined based on spring soil test levels and USU Extension-based recommendations (Cardon et al., 2008), which resulted in a gradual increase in soil test P and K (SARE 2022 FINAL Report figures: Figure 3). While pH was similar to soils on growers’ farms, salinity at the research farm was notably lower, at less than 0.5 dS m-1 across N-rate treatments, which may help explain the greater yield at the research farm and highlights the importance of following establish P and K recommendations.
Previous research highlighted that added nitrogen did not delay the onset of flowering by more than one week when rates were up to 100 kg N ha-1 (Barik, 2017; Prasad et al., 2018), while first bud was delayed by only four days when rates increased from 100 to 300 kg N ha-1 (Gupta et al., 2016). For 'Cafe au Lait' in our study, yield timing was generally earlier with increasing N fertilizer rates, apart from the first year when virus pressure overwhelmed plant response to fertilize rates. Key harvest thresholds of initial and final harvests, and 20% (T20), 50% (T50), and 80% (T80) of the total harvest were evaluated. In 2019, harvest began on August 12, or 74 days after transplant, for all application rates. Plants in the 0-rate control then reached T20, T50, and T80 at 83, 98, and 107 days after transplant, respectively (SARE 2022 FINAL Report figures: Figure 4). Plants with any N fertilizer reached T20 at 90 to 94 days, T50 at 99 to 104 days, and T80 at 106 to 112 days, with generally greater delay with increased N (Figure 4). In 2020, harvest began on August 11, or 88 days after planting, with 168 and 224 kg N ha-1 application rates, on August 24 (101 days) with 56 and 112 kg N ha-1, and on September 8 (116 days) for plants in the control. Plants with 224 kg N ha-1 first reached T20, T50, and T80 at 112, 126, and 140 days, respectively (SARE 2022 FINAL Report figures: Figure 4). Plants with 168 kg N ha-1 reached T20 and T80 next at 117 and 147 days, while plants with 112 kg N ha-1 reached T50 at 136 days and those at 168 kg N ha-1 reached T50 one day later (SARE 2022 FINAL Report figures: Figure 4). Lower rates were delayed by an additional 10 to 11 days to reach T20, zero to four days for T50, and seven to eight days for T80 (SARE 2022 FINAL Report figures: Figure 4). In 2021, harvest began on July 27 (64 days after transplant) with 112 kg N ha-1 application rate, August 2 (70 days) for the control, August 11 (79 days) for 56 and 168 kg N ha-1, and August 18 (86 days) with 224 kg N ha-1 (SARE 2022 FINAL Report figures: Figure 4). Plants with 168 kg N ha-1 reached T20, T50, and T80 first, at 106, 115, and 122 days, respectively, followed by plants with 224 kg N ha-1 that reached these thresholds one to two days later (SARE 2022 FINAL Report figures: Figure 4). Plants with lower application rates reached these thresholds after an additional two to nine days, with plants in the control delayed the most. No differences in timing were significant any year (p>0.05). Overall, planting from cuttings (2019 and 2021) appeared to hasten bloom, while starting from tubers (2020) tended to delay bloom.
As harvest timing was generally advanced with greater N application rates, we also factored in the economic optimums with recommendations that include fertilizer pricing for small farm viability, as well as soil fertility sufficiency for environmental sustainability. Through the analysis of a partial enterprise budget, soil fertility management with 168 kg N ha-1 not only produced positive returns, but was also the most economically efficient. As 168 and 224 kg N ha-1 rates produced the similar yields, hence receipts, returns were maximized with the lower rate by reducing the fertilizer input cost. With proper nutrient management yielding net returns at $18.73 m-2, dahlia represent a premium high-value crop for small farms. In Utah, cut flowers are redefining the profit potential on limited land, as more traditional high-value crops, such as red peppers, produced returns of $3.03 m-2 (Drost and Ward, 2019). Estimated returns from dahlia are similar to other state-produced cut flowers, such as snapdragons with returns of $25.70 per m2 (Lewis et al., 2021). Moreover, the timing of dahlia harvest provides growers with later season returns, thus complementing early-season cut flower crops, such as snapdragon and peony (Lewis et al., 2021; Lewis et al., 2020). As many farms rely on saving, dividing, and replanting dahlia tubers each year, greater N rates may also help increase production in subsequent years for small farms, as greater N use increased tuber production in 2021. Though tuber data in this study were limited in 2019 and 2020 from plant loss to virus, an increase in mass of potato tubers, which have similar storage and uptake mechanisms to dahlia as tuberous crops, from greater N rates has been well established (De la Morena et al., 1994).
References
Barik, I. 2017. Effect of N, P, K and Organic Manures on Flower Yield and Flower Quality of Dahlia (Dahlia variabilis) Hybrid ‘Eternity Sports’. Environ. Ecol. 35(4E): 3664-3668.
Cardon, G.E., J. Kotuby-Amacher, P. Hole, and R. Koenig. 2008. Understanding Your Soil Test Report. All Current Publications. Paper 825. <https://digitalcommons.usu.edu/extension_curall/825>.
De la Morena, I., Guillen, A., and del Moral, L. F. 1994. Yield development in potatoes as influenced by cultivar and the timing and level of nitrogen fertilization. Am. Potato J. 71(3): 165-173.
Drost, D. and Ward, R. 2019. Enterprise budgets: Red peppers with shade. 2019 Utah Agricultural Statistics and Annual Summary Report. 70–72. 29 June 2022. <https://ag.utah.gov/wp-content/uploads/2019/09/2019-Utah-Agricultural-Statistics-and-Annual-Summary.pdf>.
Gupta, Y.C., Dinesh, R.V., Kashyap, B., Bhatia, S., and Sharma, P. 2016. Effect of N and K on growth, flowering, and multiplication of Dahlia (Dahlia variabilis) cv. ‘Giani Zail Singh’. Curr. Hortic. 4(2): 48-53.
Lewis, M., Stock, M., Ward, R., Black, B., and Drost, D. 2021. Peony Cut Flower Production Budget, One Field, Northern Utah, 2020. Utah State University Extension. Paper 2166. 29 June 2022. <https://digitalcommons.usu.edu/extension_curall/2166>.
Lewis, M., Stock, M., Ward, R., Black, B., and Drost, D. 2020. Snapdragon Cut Flower Production Budget, One High Tunnel, Northern Utah, 2020. Utah State University Extension. Paper 2140. 29 June 2022. <https://digitalcommons.usu.edu/extension_curall/2140>.
Prasad, S. H., Prasad, V., Goutham, S. K., and Bose, S. C. 2018. Effect of Integrated Nutrient Management on Flowering and Flower Yield of Dahlia (Dahlia variabilis L.) CV. Kenya Orange. Plant Arch. 18(1): 795-798.
The Australian Water Quality Center. 2022. Groundwater Salinity. Groundwater Group Fact Sheet. The Department of Water, Land, and Biodiversity Conservation. <https://underdaledrillers.com.au/wp-content/uploads/2019/09/groundwater-salinity-chart.pdf>
Attachments
SARE 2022 FINAL Report figures - this file includes figures cited in the report.
Dahlia production fact sheet_submitted - this file is currently in peer-review and is therefore a draft. However the fact sheet is attached to share the amount of information we are learning about state dahlia production, much because of support for this project, which led to additional research of dahlia.
Research Outcomes
Nitrogen fertilizer application rates of 168 and 224 kg N ha-1 resulted in the greatest marketable and total yields of dinnerplate dahlia 'Cafe au Lait' when virus incidence was managed. In 2019 and 2020, the rates from 112 to 224 kg N ha-1 applications were most productive, but overall plant mortality and symptomatic response to virus infection were high and overshadowed results in the first years compared to 2021. As virus was managed by securing certified stock in 2021, yield improved and marketability increased from 26% to 66% of harvested stems. Yield in previous research, which primarily tested cultivars within a species with smaller bloom size, reached nine to ten stems per plant with rates up to 100 kg N ha-1 (Prasad et al., 2018; Barik, 2017; Gani et al., 2007). Four to six stems per plant of ‘Café au Lait’ were reached with N applications below 100 kg N ha-1, while nine to ten stems were reached at greater rates, indicating the greater N fertility need with large cultivars, such as dinnerplate types. This highlighted the importance of testing fertilizer applications greater than 100 kg N ha-1 for dinnerplate dahlia and in regions with short frost-free growing seasons, as well as reinforced the American Dahlia Society (2001) recommendation to not exceed 195 kg N ha-1.
The soil test results from the grower participants demonstrated the need for continued public outreach and extension for fertility management, and the consequences of both reliance on and overapplication of compost-based amendments. Most growers indicated annual use of composts or manures, which are associated with elevated soil test P and K, as well as elevated soil salinity in semi-arid and arid climates, which lack rainfall to leach away excess salts (Gondek et al., 2020; Hao and Chang, 2003; Stock et al., 2020). Excessive application of nutrients can also lead to greater input costs and heightened risk for runoff pollution (Pant et al., 2012). As soils accumulated P and K, and growers continued use of compost, an amendment that contains all primary macronutrients (Stock et al., 2019), the soil became enriched and reached high to excessively high fertility values. By 2021, the mean salinity value was above the 2 dS m-1 threshold for yield decline for most garden and ornamental crops (García-Capparós and Lao, 2018), while the maximum salinity value was above the 4 dS m-1, the threshold for soils to be classified as saline (FAO, 1988). Though the soil salinity thresholds for dahlia have not been quantified, their salinity tolerance for irrigation water is low, at 1.1 dS m-1 (AWQC, 2019). At the same time, the grower participant yields were the lowest in 2021, despite using certified stock, which further indicated that increasing soil salinity from nutrient management practices likely inhibited plant growth and bloom production.
As harvest timing was generally advanced with greater N application rates, recommendations should also factor in economic optimums that include fertilizer pricing for small farm viability, as well as soil fertility sufficiency for environmental sustainability. Through the analysis of a partial enterprise budget, soil fertility management with 168 kg N ha-1 not only produced positive returns, but was also the most economically efficient. As 168 and 224 kg N ha-1 rates produced the similar yields, hence receipts, returns were maximized with the lower rate by reducing the fertilizer input cost. With proper nutrient management yielding net returns at $18.73 m-2, dahlia represent a premium high-value crop for small farms. In Utah, cut flowers are redefining the profit potential on limited land, as more traditional high-value crops, such as red peppers, produced returns of $3.03 m-2 (Drost and Ward, 2019). Returns from dahlia are similar to other state-produced cut flowers, such as snapdragons with returns of $25.70 per m2 (Lewis et al., 2021). Moreover, the timing of dahlia harvest provides growers with later season returns, thus complementing early-season cut flower crops, such as snapdragon and peony (Lewis et al., 2021; Lewis et al., 2020). As many farms rely on saving, dividing, and replanting dahlia tubers each year, greater N rates may also help increase production in subsequent years for small farms, as greater N use increased tuber production in 2021. Though tuber data in this study were limited in 2019 and 2020 from plant loss to virus, an increase in mass of potato tubers, which have similar storage and uptake mechanisms to dahlia as tuberous crops, from greater N rates has been well established (De la Morena et al., 1994).
In conclusion, proper nutrient management is vital for optimal production of dinnerplate dahlias. This study established that nitrogen rates of 168 and 224 kg N ha-1 produced the greatest yields, while application of 168 kg N ha-1 was the most economically efficient by reducing input costs without a change in yield. Regular soil testing and following nutrient application rate recommendations are critical for sustainable soil fertility management. Using soil amendments, such as compost to reach soil test phosphorus and potassium requirements and supplementing additional nitrogen needs with N-only fertilizers helps maintain optimal macronutrient levels without excessive buildup of nutrients or salts. Virus screening is also critical for dahlia production, which severely stunts production and is widespread.
References
Australian Water Quality Centre (AWQC). 2019. Groundwater Salinity. Department of Water, Land and Biodiversity Conservation. Groundwater Group Fact Sheet. 10 August 2022. <https://underdaledrillers.com.au/wp-content/uploads/2019/09/groundwater-salinity-chart.pdf>.
Barik, I. 2017. Effect of N, P, K and Organic Manures on Flower Yield and Flower Quality of Dahlia (Dahlia variabilis) Hybrid ‘Eternity Sports’. Environ. Ecol. 35(4E): 3664-3668.
Cardon, G.E., Kotuby-Amacher, J., Hole, P., and Koenig, R. 2008. Understanding Your Soil Test Report. Utah State University Extension. Paper 825. 29 June 2022. <https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1825&context=extension_curall>.
De la Morena, I., Guillen, A., and del Moral, L. F. 1994. Yield development in potatoes as influenced by cultivar and the timing and level of nitrogen fertilization. Am. Potato J. 71(3): 165-173.
Drost, D. and Ward, R. 2019. Enterprise budgets: Red peppers with shade. 2019 Utah Agricultural Statistics and Annual Summary Report. 70–72. 29 June 2022. <https://ag.utah.gov/wp-content/uploads/2019/09/2019-Utah-Agricultural-Statistics-and-Annual-Summary.pdf>.
Food and Agriculture Organization of the United Nations (FAO). 1988. Salt-Affected Soils and their Management. Bulletin 39. FAO, Rome. 10 August 2022. <https://www.fao.org/3/x5871e/x5871e00.htm#Contents>.
Gani, G., Beigh, M. A., Lone, R. A., Nanda, A. B., and Hussein, K. 2007. Effect of different levels of nitrogen and phosphorus on growth and flowering of dahlia cv. ‘Kenya yellow’. J. Plant Sci. Res. 23(1): 59–62.
Gondek, M., Weindorf, D. C., Thiel, C., and Kleinheinz, G. 2020. Soluble salts in compost and their effects on soil and plants: A review. Compost Sci. Util. 28(2): 59–75. DOI: 10.1080/1065657x.2020.1772906.
Gupta, Y.C., Dinesh, R.V., Kashyap, B., Bhatia, S., and Sharma, P. 2016. Effect of N and K on growth, flowering, and multiplication of Dahlia (Dahlia variabilis) cv. ‘Giani Zail Singh’. Curr. Hortic. 4(2): 48-53.
Hao, X. and Chang, C. 2003. Does long-term heavy cattle manure application increase salinity of a clay loam soil in semi-arid southern Alberta? Agric. Eco. Environ. 94(1): 89–103. DOI: 10.1016/s0167-8809(02)00008-7.
Lewis, M., Stock, M., Ward, R., Black, B., and Drost, D. 2021. Peony Cut Flower Production Budget, One Field, Northern Utah, 2020. Utah State University Extension. Paper 2166. 29 June 2022. <https://digitalcommons.usu.edu/extension_curall/2166>.
Lewis, M., Stock, M., Ward, R., Black, B., and Drost, D. 2020. Snapdragon Cut Flower Production Budget, One High Tunnel, Northern Utah, 2020. Utah State University Extension. Paper 2140. 29 June 2022. <https://digitalcommons.usu.edu/extension_curall/2140>.
Prasad, S. H., Prasad, V., Goutham, S. K., and Bose, S. C. 2018. Effect of Integrated Nutrient Management on Flowering and Flower Yield of Dahlia (Dahlia variabilis L.) CV. Kenya Orange. Plant Arch. 18(1): 795-798.
Stock, M., Maughan, T., and Grossl, P.R. 2020. Urban Garden Soils: Testing and Management. Utah State University Extension. Paper 2116. 29 June 2022. <https://digitalcommons.usu.edu/extension_curall/2116>.
Stock, M., Maughan, T., and Miller, R. 2019. Sustainable Manure and Compost Application: Garden and Micro Farm Guidelines. Utah State University Extension. Paper 2047. 10 August 2022. <https://digitalcommons.usu.edu/extension_curall/2047>.
Education and Outreach
Participation Summary:
- Consultations: conducted two to four times per on-farm participant in the study, as well as two additional flower farms (8 priority farms in Utah). The first consultation was on 5/24/19, during which dahlia production strategies and soil fertility/sampling were discussed with farm participants (6 farms). The second consultation was on 9/6/19 with seven farms due to a viral outbreak that occurred at the USU research farm. Dr. Stock began a new partnership with USU Plant Pathologist, Dr. Claudia Nischwitz; together they traveled to flower farms to consult on pest and viral disease presence, survey farms, and collect plant tissue for lab testing. A follow-up consultation occurred electronically on 10/13/19 to update farms on lab results and best management practices, as the viral outbreak was found across the state. A final consultation in 2019, was on 11/1 with the six farms in the study. Retrieving tubers, soil testing, and pests and disease were discussed. The following year, due to COVID-19, in-person visits were not possible and we pivoted to email, postal, phone, Instagram, and Zoom correspondence methods. Because travel was restricted, we mailed plant material, data sheets and postage for sending in soil samples to each farm, coordinating efforts over email. We did this with each farm in May 2020 and October 2020, as well as in May and Oct of 2021. During the growing season, we also provided direct consultation to growers in and outside of the study to troubleshoot production issues. In Sept 2021, we also toured six additional farms for dahlia production challenges - soil, nutrient, and irrigation management, as well as disease.
- Online training: two videos were produced regarding basic soil nutrient management and health. The first video was a step-by-step tutorial for collecting appropriate soil samples in a microfarm or garden bed. The second online training is a guide for interpreting soil test results from the lab - what the results mean and how to follow recommendations. The videos were promoted and shared to Instagram and Facebook (IGtv and FBwatch. The videos were viewed 1,331 times and 1,659 times, respectively, in 2019. At the USU Urban and Small Farms Conference in 2021, one of the on-farm participants presented on cut flowers marketing and sales, directly including 'Cafe au lait' dahlias as one of the most profitable and reliable sales for growers. In 2021, a presentation on soil health was given based on sustainable nutrient management at the Utah Urban and Small Farms Conference. In 2022, a presentation on dahlia production and trial findings was given at the Utah Urban and Small Farms Conference. This webinar was recorded and can be viewed here: https://www.youtube.com/watch?v=akrSA7q5S9I&list=PLMnDQoXFVBEbhN_ZJ5fGZts81Dd2Xftjm&index=20 (237 views of the recording as of Oct 2022).
- Published press articles, newsletters: In 2019, Dr. Stock co-established and became a board member of the Utah Cut Flower Farm Association with top growers in Utah (website: https://www.utahflowerfarms.com/). The Association now has 140 members, monthly zoom webinars, and quarterly gatherings (e.g. farm tours and events). As part of the Association’s quarterly newsletter, Dr. Stock authored one newsletter article in August 2019 to provide an overview of USU cut flower research to growers, and a second in October 2019 to detail dahlia management and lessons learned from the 2019 USU trials. In Dec 2021, a mini-grants program was established with the UCFFA that I chair to encourage farmers to explore innovative ideas that improve regional production, learn to discriminate sources of background information, and build confidence to then apply for larger national grants. To date, this has inspired one farm to apply for a grant through the national Association of Specialty Cut Flower Growers (ASCFG) and be selected for funding - her research is on dahlia production and investigating deficit irrigation. With Western SARE's outreach efforts, two cut flower farmers will likely apply for a Farmer/Rancher grant in 2022. In 2021, Dr. Stock co-authored an ASCFG article in the Cut Flower Quarterly (Fall Edition): "Tackling the three challenges of dahlia production: bloom timing, nutrient management, and disease." 2021-Fall-Stock-and-Nischwitz-Tackling-the-three-challenges-of-dahlia-production. In 2022, we finalized a dahlia production fact sheet for USU Extension (in review). A draft is included here: Dahlia production fact sheet formatted in progress.
- Webinars/talks/presentations: We produced one presentation on dahlia production at the 2020 Utah Urban and Small Farms Conference (04 Mar. 2020). There were approximately 60 attendees. In 2022, we presented on dahlia production and trial findings at the Utah Urban and Small Farms Conference (2/23/22). There were 122 attendees. This webinar was recorded and can be watched here: https://www.youtube.com/watch?v=akrSA7q5S9I&list=PLMnDQoXFVBEbhN_ZJ5fGZts81Dd2Xftjm&index=20. There have been 236 views as of Oct. 2022.
- Workshop/field days: We hosted a high tunnel workshop on general horticulture production practices that was followed by a hands-on farm tour on May 22, 2019. There were 60 attendees from Utah and Idaho. At this event, Dr. Stock gave two workshop presentations (one on soil management in horticultural systems and one on general cut flower production practices) and a farm tour of the cut flower trials, including the dahlia study. Dr. Drost and Black (co-PIs) discussed other production factors, such as temperature management, farm site selection, and other horticultural crops. On March 24, 2022, we hosted a farm tour for season extension techniques that highlighted fruits, vegetables, and cut flowers (Dr. Stock led the cut flower session). 52 growers attended.
- Other Educational activities: A survey at the 2019 Utah Urban & Small Farms Conference indicated 58% of cut flower growers preferred Instagram to any other social media platform (Facebook was second-most popular at 33%). In response to this demand, we created the @usu_smallfarms account on Instagram and Facebook (with primary focus on Instagram). This account has been popular in connecting with growers and successful in sharing real-time information, as well as engaging educational content. We developed and shared 11 posts regarding the SARE dahlia study (see @usu_small farms on IG for posts). These posts ranged from soil nutrient management, to harvest practices, to pest and disease identification and management as outbreaks occurred, and tuber storage. Social media content related to dahlia production from this grant averaged a 21% engagement rate among followers (>6% is considered high). As of October 2022, the account has over 2,500 followers that include state, regional, and national cut flower growers (see map of followers).
This project initiated a cut flower research and extension program at Utah State University and much was learned to effectively communicate with this demographic of growers. Utah cut flower farms increased from less than 40 farms in late 2018 to 135 farms in 2022 (see map below for number of known cut flower farms by county), a Utah Cut Flower Farm Association was established in 2019 to serve Utah and surrounding communities, and Utah's Urban and Small Farms Conference has now hosted a half-day cut flower session each year since 2019. Most cut flower farmers are women in their 20s to 40s with fewer than 10 years of experience in farming, and savvy with technology. We found using Instagram was the most effective means for continuous communication , and was supplemented with USU Extension fact sheet publications, grower conferences, and farm tours.
Instagram facilitated incremental knowledge building through multiple posts per week, which ranged from research updates that helped followers engage with the trial remotely to timely alerts and management recommendations, as well as recruiting for additional trials and conducting informal surveys on crops. We also used Instagram to follow cut flower farms - this allowed us to remotely scout farms for production trends and challenges, thus keep up-to-date on farmers' needs in between more formal communication periods (farm visits, phone calls, etc). We established @usu_smallfarms in early 2019, and the account has over 2,500 followers, 415 posts, and over a 5% engagement rate (a total reach of 352,133 accounts and 397,055 impressions), as of October 2022. Each post features a descriptive picture with an informative, often action-oriented caption. Melanie Stock authored a peer-reviewed journal article in HortTechnology detailing best practices for Instagram use in Extension as a result (Stock, 2020).
In addition to social media, more traditional forms of outreach were also used. As cut flower production in the US Mountain West faces unique environmental challenges (high elevation solar radiation, extreme temperature fluctuations, limited soil and water quality, and uncertain water quantity), developing regional production guides has been important. This has also helped us combat misinformation online. We published peer-refereed guides on production (7), economic budgets for cut flowers (6), and resource management (4). A fact sheet on: dahlia viruses is accepted and in press, on production is in review, and a budget for producing dahlias is in preparation. Dahlias have been our most complex cut flower crop to grow and funded research that built upon Western SARE initiatives were needed to complete these dahlia fact sheets as we discovered more challenges with production beyond soil nutrient management. Our fact sheets for soil nutrient management and use of compost and manure for small farms have been some of the most popular USU Extension downloads, with over 5,000 recorded.
Creating a hub with relevant fact sheets has been important for integrating traditional and new forms of outreach. We have two websites as a result, one managed by USU Extension (flowers.usu.edu) and smallfarmslab.com, which allows for greater flexibility in content delivery. We also have had success in recording webinars and posting to USU Extension's YouTube channel for additional views.
In-person connections continue to be important. Farm tours allowed growers to open up on additional challenges and successes, but providing written feedback helped growers implement changes. We created tables of yearly soil test values for each farm in 2021, then a nutrient management recommendation. Seeing the annual information in one place was most meaningful. Hosting grower conferences, such as the Utah Urban and Small Farms Conference, worked well both in-person and online. More participants were able to attend the online format (participation doubled from 60 attendees at a given in-person talk to 122), which also allowed for recordings to be posted for additional views. We found presenting basic concepts through presentations was effective in-person or online. In 2022, we supplemented the online conference with an in-person field day one month later. This allowed us to invite growers (60 attended) to our research farm and demonstrate concepts from the conference. Covid-19 created a new normal for online education that was best supplemented with targeted in-person events.
Education and Outreach Outcomes
The timing of this project spanned both an unprecedented surge in cut flower farming - a dynamic new crop for small farms that are predominantly run by an under-represented demographic in agriculture - and a global pandemic. From this, we learned the importance of diverse programming that creates flexibility and the ability to pivot during unanticipated events, such as COVID-19. Because cut flower farmers were a new demographic for extension, we surveyed the farmers early on to determine which educational platforms they preferred. This allowed us to streamline and diversify our tools for meaningful outreach, while not overextending our capacity. In-person workshops and farm tours, webinars, fact sheets, and social media (Instagram) were the key traditional and new tools for us to integrate. Instagram allowed us to share incremental information, such as timely farm operations and reasoning, crop alerts, and demonstrations of activities at our research farm. Posts with a representative picture and detailed action-oriented caption resulted in greatest engagement, and added transparency and inclusion with our research. It also allowed us to promote published fact sheets and educational websites to offer additional information and for authors to have greater engagement with their content. Social media is known for showcasing content in the best light; we opted to show the raw - sometimes unfortunate - aspects of crop production on our research farm, which included productive harvests to devastating disease outbreaks. This helped us increase our relatability with our audience, as well as create teachable moments. As a result, we have built strong engagement (over 2,500 followers) and trust, and farmers have increased their knowledge. This also helped supplement less frequent in-person events and webinars, where much information is shared in a limited time and can be overwhelming. Revisiting key topics, but in smaller "chunks" on social media helped us increase our impact. We found that presenting basic information in webinars, and recording the webinars to post on YouTube was also highly effective, as it increased flexibility for participants. Using in-person events for very targeted outreach, such as demonstrations at our research farm, made the most out of our programming. We also found the Cooperative Extension Fact Sheets are still highly relevant. Farmers want to refer to printed information from a source they trust (often it can be difficult to distinguish reputable sources on the internet). Therefore, the extension brand is important to grow online. My fact sheets have been downloaded over 11,000 times since 2019. Several fact sheets have been converted to HTML websites by USU Extension; the number of clicks with this content is unknown.
We were fortunate to receive Western SARE funding in 2019 to study cut flowers, which were just taking off as a new crop for small farms in Utah. This helped us established early programming and grow with the farmers, providing extension resources along the way. One of our most important findings from this has been the need for additional outreach regarding soil fertility and the challenge in combatting misinformation online regarding nutrient management and soil health. The use of compost (and manure) and a "more is better" approach has become strongly engrained with small-scale producers, while messaging regarding soil testing, sustainable nutrient application rates, and environmental pollution from excessive loading is missing. Providing soil testing and one-on-one consultations has been key for helping growers reframe their soil management and avoid overapplication. Our hands-on approach with farmers has increased adoption of recommendations and information sharing between farms, which is often more meaningful that information from university to farm, as farmers can uniquely relate and have inherent trust. During the project, we published three peer-reviewed fact sheets dedicated to soil testing and nutrient management on small farms, as previously existing materials were directed at larger, agronomic farms or home gardeners, and thus our small farm demographic lacked appropriate extension materials. However, once soil fertility has reached excessive values, several years are needed to reach optimum levels once again under best management practices. In this study, there was overall a slow decline in soil test levels that were still greater than desired. Ongoing outreach will be important, especially as new farms rapidly establish each year.
Soil nutrient management in Utah - the importance of soil testing to understand existing nutrient levels, particularly phosphorus, potassium, and soil salinity levels before applying fertilizer.
Soil nutrient management in Utah - understanding fertilizers and soil amendment guaranteed analyses, and selecting sources that are low in phosphorus and potassium when soil tests indicate high levels.
Soil nutrient management in Utah - compost production and use with saline soils, excessive phosphorus and potassium soil test levels.
Soil Health - tillage ("to till or not to till")
Pest and disease management - identifying problems, subscribing to USU IPM updates, and control methods.