Final report for LS18-297
Tea, Camellia sinensis, is currently under investigation as a potential new crop for growers in the southeastern United States. Tea is the second most consumed beverage globally, behind water, and the U.S. is the third largest importer of tea. Although tea can be grown in many parts of the U.S., and there are tea growers in at least 16 states, Hawaii is the only state with an established, extension-supported tea industry, and research to support mainland growers is lacking. Projects underway at the University of Florida and Mississippi State University are investigating regional suitability of currently available U.S. tea genotypes, but no work has yet been done examining sustainable production systems for the Southeast, particularly from economic and environmental standpoints. This work proposes to examine several cover and shade cropping systems for tea production in an effort to identify a growing system that favors establishment and productivity of tea while minimizing weed and disease pressure, and building a health soil microbial population capable of cycling nutrients and maximizing resource use efficiency.
- Establish cover cropping systems at three sites, and examine the impacts of each system on tea plant growth and physiology, leaf yield and quality, weed and disease incidence, nitrogen and water use efficiency, and specific aspects of the soil microbial community related to nutrient cycling.
- Incorporate a hands on educational opportunity for cohorts of graduate students who will directly assist growers with implementation and refinement of tea cropping systems that are sustainable in the Southeastern U.S.
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Site establishment. Cover-and-shade cropping systems were established at two partner grower field sites, in Reddick (USDA zone 9a) and High Springs (USDA zone 8b), using a randomized complete block in a split-split plot design with three replications. The components tested in this system were shade tree type (moringa vs. persimmon), ground cover (rhizoma peanut vs. cowpea-crimson clover rotation), and tea variety (three). A total of 216 plants were planted under cover and shade at each site. An additional 54 plants (18 each variety) were established at each site under weed cloth as a no-cover, no-shade control. Each field site was prepared with overhead irrigation in the cover crop areas, and drip irrigation lines at a 100-cm row spacing in both cover and control plot areas. Tea was planted in the center row of each block, spaced at 60 cm intervals within rows, and shade trees were planted on a 4 m within row spacing in the first row of each block, and in an additional row beyond the final block, for a 4 by 3 m starting grid. This is denser than the typical 6 to 8 m starting grid described by Hadfield (17), to allow us to establish shade more rapidly in the experimental plots. As is common practice in shade-grown tea, trees will be thinned as canopies mature to maintain even, partial shade. Perennial peanut sod was established in late summer of 2018, and the remaining treatments were installed in the fall of 2018. Three varieties of tea were selected for this study, based on our observations from an ongoing tea varietal trial conducted under North Central Florida conditions, and on plant availability; the varieties included were ‘Fairhope,’ ‘Large Leaf,’ and ‘Red Leaf.’
1. Impacts of cover-and-shade systems on tea growth, physiology, yield, and quality. Tea plant growth was tracked with stem caliper measurements and pruned biomass. PSII efficiency was measured in the second year of the study through the use of chlorophyll fluorescence. The timing of yield and quality analyses were necessarily determined by plant growth. Initial harvests were conducted during August and September of 2021, providing preliminary yield data. However, quantities harvested were insufficient for extensive quality analysis. Tea leaf quality is highly correlated with polyphenols and caffeine, and may be assessed by measuring these compounds in leaves or made tea. We have developed and tested a protocol to process harvested green tea and extract and quantify total phenolics using the limited amount of leaves harvested during the grant period. Future work will use quantification of specific polyphenols (epigallocatechin gallate, epigallocatechin, epicatechin gallate and/or epicatechin) and caffeine concentrations in leaf extracts measured with HPLC-mass spectrometry methods (28, 29) to assess impacts of ground cover and shade on tea quality. These analyses will be conducted as soon as sufficient material may be harvested from the plants.
Upon plants reaching harvestable age, nitrogen and water-use efficiency (NUE, WUE - harvestable biomass vs. nitrogen and water applied, respectively) will be calculated for each system at relevant harvest dates for each crop. Annual NUE and WUE values will be calculated for the systems. Because tea plants typically reach harvestable size in their fourth year and canopy closure between six and seven years, these analyses were not completed within the time frame of the grant period; however water and nitrogen input data collected during the study will be critical for these longer-term objectives.
2. Weed suppression. Weed cover was monitored within each growing system. Percent cover for weeds versus cover crop was assessed within quadrats of fixed areas adjacent to tea plants within rows. Quadrats were photographed from above, and images were analyzed by manually marking either cover crop or weed areas, and using image processing software (GIMP 2.10) to calculate the marked area as a percentage of the total image.
3. Soil Heath Parameters. Bulk and rhizosphere soil samples were collected at two years after planting for analysis of microbial components. Segments of the microbial communities were assessed in each treatment by quantification of an array of specific prokaryotic genes known to be involved in nutrient cycling via quantitative PCR (qPCR). Genes studied included nifH (involved in nitrogen fixation), amoB and amoA (Bacterial and Archaeal genes involved in nitrification), nirK/S (genes involved in denitrification), and phoD (genes encoding phosphatases). The culturable component was evaluated via dilution plating on three media types (APDA, R2A, and Nitrogen-Free, NF), providing a check on genetic information and allowing a limited estimation of microbial richness. Soil samples were also evaluated for organic matter, nitrogen (TKN, NO3-N, NH4-N), phosphorus, calcium and magnesium. Based on observed differences in genetic capacity for nitrogen cycling (quantification of genes, above) between soil under weed barrier cloth and perennial peanut cover, bench and field microplot studies were conducted to confirm differences in nitrogen mineralization between these soils. Organic fertilizer was added to soils under controlled conditions (temperature gradient, consistent moisture) in growth chambers, and also in microplots (pvc tubes) installed in the Williston field site. Nitrogen fractions (TKN, NO3, and NH4) were monitored weekly for four weeks to track rates of fertilizer mineralization.
4. Disease incidence and pathogen ecology. Disease incidence and severity were monitored in all plots throughout the study for comparison among growing systems and site locations. Based on previous studies, anthracnose (brown blight), caused by Colletotrichum camelliae, was expected to be the predominant disease problem (30), and was therefore the focus of incidence and severity assessments. Plants were also monitored for additional pathogenic species. Root samples from both declining and asymptomatic plants were collected at the end of the second growing season and examined to monitor for root knot incidence, as incidence without apparent symptoms would indicate tolerance in this crop.
In order to assess potential impacts of ground covers on tea pathogen survival, we conducted bench studies to examine survival of Colletotrichum isolates on cover crop residues from each growing system, and mesh litter bag studies to analyze viability of infected leaf litter over time at each site. For bench studies, bulked cover crop residues from each cover-shade combination were inoculated with a conidial suspension of Colletotrichum camelliae, isolated from tea, and incubated in a growth chamber under environmental conditions set to approximate outdoor conditions. Samples were removed and plated on a semi-selective medium for isolation of Colletotrichum spp. (31) at 7-day intervals from time of inoculation, until no Colletotrichum was recovered at two subsequent samplings. For mesh bag studies, infected leaves were collected from field and greenhouse-grown plants and placed in mesh bags on the soil surface, beneath cover crop standing biomass and litter. Bags were removed at weekly intervals, and the leaf tissue was plated on semi-selective media for recovery of Colletotrichum. This study was repeated four times to capture both warm and cold weather conditions.
5. Tea varietal assessment. Varieties included in the study were compared for survival, growth (as caliper size and biomass production), leaf nutrient status, and disease incidence and severity. Effects of tea varieties on soil microbial components were also analyzed.
6. Hands-on training in service of growers and students. We utilized an existing “Project Team” course at UF (ALS 4932/6932) to deliver outreach to growers and training for undergraduate and graduate students. This course brings together a group of 7-10 students with a producer mentor and faculty facilitator to address real-world issues and challenges faced by agricultural professionals. Our cooperating producers participate in mentoring these classes by providing real production challenges noted within these tea systems, including possible disease, weed, soil, water, and nutrient issues. To address these issues, each class delivers in-depth investigations utilizing on-the-ground assessments coupled with literature synthesis, consultation with disciplinary experts, and other industry stakeholders. This Project Team approach brings benefits to both the growers and the students. Students learn professional development skills delivered during the course, emphasizing the following areas: professionalism; project management; working in interdisciplinary teams; practicing oral and written communication among team members and stakeholders; considering creative and novel solutions combining multi-disciplinary approaches to tackling problems; and formulating, designing, and presenting approaches effectively. Students also gain practical, hands-on experience in addressing relevant sustainable production challenges. Our growers benefit from these Project Teams by having a “rapid response” to emerging issues, interaction and mentorship of prospective employees or new professionals, and tighter linkages with our extension and academic programs.
Objective 1. Although this project has allowed us to establish experimental cover-and-shade plots for tea production, we recognized that a three year grant period would not be sufficient to establish mature shade trees, and the tea plants would only begin to be productive at the end of the project, so the full impacts of shade and yield comparisons would not be realized within the study period. However, the suitability of shade tree species for tea Florida production could be tested, and plots were designed to allow future planting of additional tea rows after tree establishment. We worked with the partner growers to select two shade trees that offered promising architectural characteristics and also provided added value for the growers. We found that moringa was not a suitable shade tree within the study region. Despite successful production of moringa on one of the cooperator farms, moringa planted within the tea plot areas had exceptionally high mortality (>80% at both sites) over the first winter. The moringa production area was located in a relatively sheltered part of the farm, near a building, which may have created a suitable microclimate, while the tea plots at both sites were in more open areas. Moringa plants that did survive the winter were not sufficiently quick to resume growth in the spring, and it was concluded that they would be unlikely to produce sufficient shade by June each year, when tea plants would be most impacted by intense sunlight and heat. The moringa plots were replanted with dwarf everbearing mulberry in July of 2019. This tree was selected for its rapid growth and potential value-added fruit crop, and so far appears to be establishing well. Our initially-proposed swamp dogwood was replaced with persimmon prior to site establishment, based on grower preference for a fruit tree. The persimmon trees have established successfully and began bearing fruit during the final year of the study, but have a smaller, denser canopy, which may not prove as beneficial for the tea plants.
We also determined that cowpea was not a suitable cover crop for our tea production systems. The cowpea provided total cover, successfully outcompeting all weeds, but was too aggressive: it also completely covered the young tea plants, and vined up the shade trees, nearly smothering them as well. In consultation with the growers, we planned to replace cowpea with alyce-clover in the rotation plots during spring of 2020; however, Covid-shutdowns resulted in inability to access the sites during the spring planting window, and a poor seed-production year resulted in inability to purchase sufficient alyce-clover seed. We attempted a late planting with a recommended heat-tolerant white clover, but establishment was poor. At this point, the annual rotation plot was transitioned to winter crimson clover / summer natural vegetation rotation for the duration of the study.
Growth of tea plants at the end of their first year was assessed with stem diameter differences (caliper measurements) and pruned biomass (fresh weights). Significant differences were evident in both survival and biomass production after one year. At the High Springs site, ‘Large Leaf’ plants had higher survival and greater pruned biomass than both ‘Fairhope’ and ’Red Leaf’ (p<0.01). No differences were detected in tea plant survival between perennial peanut and rotation cover (Fisher LSD, p=0.79), but plants in perennial peanut cover plots had significantly greater pruned biomass than those in the cowpea rotation (p<0.01). At the Williston site, there were no significant differences in survival by either variety or cover type, but both factors significantly impacted biomass production. ‘Large Leaf’ produced greater biomass than both ‘Fairhope’ and ’Red Leaf’ (P<0.01), and ‘Fairhope’ produced greater biomass than ‘Red Leaf’ (p<0.05). At this site, plants in the control plot produced greater biomass than those in either cover crop, and plants in the perennial peanut cover produced greater biomass than those in the cowpea cover (p<0.01). Initial yield data collected in 2021 indicated that both variety and cover type significantly impacted yields (p<.01). ’Red Leaf’ yields were extremely small, and were not included in the analysis for this season. ‘Fairhope’ produced higher yields than ‘Large Leaf’(p<0.001), and plants produced higher yields with weed barrier cloth than with either perennial peanut (p=0.006) or clover rotation (p=0.022) cover. The effect of cover was more pronounced with ‘Fairhope’ than with ‘Large Leaf’ (interaction p=0.06).
The High Springs site was compromised during the spring of 2020, due to a combination of an unforeseen loss of partner grower capabilities and Covid-related travel restrictions. Despite efforts throughout the summer to recover the site, it was determined that the data from this site were no longer reliable, and analyses for 2020 included only the Williston site. Through the second growing season, we saw higher tea mortality in the weed barrier cloth control plots than in the companion cover plots (81 vs. 90% survival, overall).
Objective 2. Due to the determination that the cowpea cover is unsuitable for the production system (described above), weed cover analyses were not conducted during the first growing season. Cowpea suppressed weeds exceptionally well, but also suppressed tea plant growth and inhibited plant maintenance activities. Perennial peanut cover was analyzed near the end of the second growing season. Although it persisted well and had begun spreading into adjacent rows, its average cover was only 27%. Though not sufficient to be considered weed "suppression," our soil analyses showed that this was sufficient to positively impact both chemical and biological soil properties (nitrogen content, microbial composition and activity).
Objective 3. Significant differences were observed among treatments in both soil nutrients and indicators of microbial nutrient cycling capacity. By the second growing season, soil organic matter and most soil nutrients measured (NO3-N, TKN, K, Ca, Mg) were significantly lower under weed barrier cloth than under one or both of the companion cover crops. Analysis of prokaryotic genes involved in nutrient cycling via quantitative PCR (qPCR) showed higher nutrient cycling potential (significantly higher presence of microbial genes, and genes specifically associated with nitrogen and phosphorus cycling) under companion cover crops than under weed barrier cloth, with 16S, AOA, nirK, nirS, nifH, and phoD quantities significantly higher in both companion covers, and AOB higher only under perennial peanut (manuscript in preparation). Culture plating results also demonstrated higher counts of bacteria capable of growing on nitrogen-free medium (NF) in soil under cover crops, confirming that higher numbers of genes present are correlating with higher numbers of organisms expressing these genes, at least among the culturable portion of the population. Bacterial and fungal counts (CFU) were both significantly higher under perennial peanut than either clover rotation or weed barrier cloth treatments.
Objective 4. Disease incidence was low at both sites during the first season, and no new pathogens were described from either site. Ground cover and variety did not have apparent impact on anthracnose through the first two growing seasons. In August of 2020, effects of variety and cover were both non-significant. However, in spring of 2021, anthracnose incidence was significantly higher in plants grown with companion ground covers than in plants on weed barrier cloth, and differences emerged among varieties as well, with lower disease in the ‘Fairhope’ plants than in ’Red Leaf’ and ‘Large Leaf.’ Unusual winter weather is a likely factor in the sharp increase of disease between fall and spring ratings, and to varietal differences, and disease subsequently returned to low levels. Root knot nematodes were not detected in either declining or asymptomatic plant root samples. A new Colletotrichum species for tea in the US was detected at one of our common garden partner sites; Koch’s Postulates have been completed for this new report; phylogenetic analyses are being conducted to properly place the isolate taxonomically prior to submitting a Disease Note for publication. Pathogen survival studies showed that survival in tea leaf litter was highly seasonal, with lower recovery under warmer temperatures, and was generally lower on weed barrier cloth than in companion cover crops.
Objective 5. Tea plants of the three varieties used in this study have been placed with a common garden partner in Bartow, FL, and additional plants have been shared with growers through Florida A&M University Extension and planted on the FAMU campus. These plantings will be monitored for survival and growth, providing preliminary data for these varieties over a wide geographical range.
Objective 6. The first project teams course to focus on tea was taught during the fall of 2019. Students in this class focused on needs analysis and study design, and crafted a research proposal for examination of nitrogen application rates in multiple tea varieties for yield and quality optimization. The follow-up course, expected to implement the trial, was postponed due to Covid-19-related logistics limitations and could not be completed within the grant period. This will likely be completed as a research internship within the academic year 2022-2023.
The use of weed barrier cloth (WBC) for weed management in Florida tea production presents several sustainability trade-offs. Though WBC was highly effective in weed management and resulted in more rapid tea plant growth, we found that nutrient cycling processes under WBC were significantly impaired within only two growing seasons. Colletotrichum camelliae, the causal agent of anthracnose at our sites, had reduced survival in infected leaf litter on WBC, relative to living “green mulch” ground cover, but the impact of this inoculum source was not clear. Differences in disease levels appear to be driven primarily by plant stresses, and competition with living cover plants may also contribute to the higher disease observed in cover treatments following extreme weather events. The three tea varieties tested varied in their survival, growth, disease severity, and early yields. Our study thus identified key variables important in managing tea under a cover crop system and indicated that legume cover crop could improve nutrient cycling in the soil by fostering microbial biodiversity.
Educational & Outreach Activities
Project participants gave 11 oral or poster presentations during the grant period, at local and national meetings and at a grower field day event. Due to the Covid-19 pandemic, the field day even was held online, which resulted in a wider geographical reach and the production of reusable educational products, including a video tour of the tea program and SARE project and recorded field day presentations. A total of 126 people registered for the event, and had access to the online recordings. Of those, 68 attended all or part of the event synchronously. One manuscript is under preparation, pending pathogen DNA sequencing and phylogenetic analysis, and one extension publication is expected within the second year. A social media site has been initiated on facebook. Two new collaboration teams have been initiated, one state-wide and one national, with a focus on tea research.
Posters & Oral Presentations:
Orrock, J, and Richter, B.S. (2019) Diversity of Colletotrichum species on tea (Camellia sinensis) from three counties in Florida. Annual meeting, American Phytopathological Society, Cleveland, OH. Poster.
Clarke, C., Spakes Richter, B., Rathinasabapathi, B (2021) Genetic characteristics and provenance of tea (Camelia sinensis) plants collected in the United States. American Society for Horticultural Science, Annual meeting, Denver, CO. Poster.
Clarke, C., Spakes Richter, B., Rathinasabapathi, B. (2021) Total phenolics as an indicator of quality in Florida-grown tea. Annual meeting, Florida State Horticultural Society, Daytona Beach, FL. Oral Presentation.
McAmis, S., Rathinasabapathi, B., and Spakes-Richter, B. (2021) Ground Cover Growing Systems for Tea Production in Florida. Annual meeting, Florida State Horticultural Society, Daytona Beach, FL. Oral presentation.
Richter, B.S., Soltez, K. and McAmis, S. (2021) Impacts of ground cover and plant variety on anthracnose in tea (Camellia sinensis). Annual meeting, American Phytopathological Society, online. Interactive poster.
Rathinasabapathi, B. (2021) Tea variety trails for production in Florida. Tea Virtual Field Day, May 21, 2021. Oral presentation.
McAmis, S. (2021) Shade and ground cover growing systems for tea production in Florida. Tea Virtual Field Day, May 21, 2021. Oral presentation.
Soltez, K. (2021) Tea disease update and pathogen survival. Tea Virtual Field Day, May 21, 2021. Oral presentation.
Clarke, C. (2021) Tea germplasm and breeding efforts. Tea Virtual Field Day, May 21, 2021. Oral presentation.
Clarke, C. (2021) Tea processing demonstration. Tea Virtual Field Day, May 21, 2021. Oral presentation.
Fisher, P. (2021) Camellia and other superfoods for tea production. Tea Virtual Field Day, May 21, 2021. Oral presentation.
Sapp, L. Tea as an alternative crop for north Florida. Florida A&M University Extension newsletter, Spring, 2022.
Manuscripts in preparation:
McAmis, S. Rathinasabapathi, B., Ogram, A., Bae, H., and Richter, B.S. Impacts of ground cover on soil nitrogen cycling and plant health in a tea production system.
Orrock, J, and Richter, B.S. First Report of Colletotrichum **** as a pathogen of tea (Camellia sinensis) in Florida.
This project focuses on an emerging perennial crop, which requires approximately 6-7 years to reach maturity (profitable harvest), but which is then expected to remain productive for 40-100 years, depending on plant health. The project generated ready-to-implement knowledge about the trade-offs in growing system components, as they impact plant establishment and early growth, disease incidence, soil nutrient status, and soil nutrient cycling capacity. The project also established a long-term grower-cooperator research site, where research on ground cover, shade effects, and pests and diseases of tea is ongoing.
Given the crop’s emerging status, the number of current tea growers is still small, and the field day outcomes assessment focused on grower interest and intention. The field day respondents had overall higher attitude levels as compared to knowledge levels. The high levels are encouraging for the future development of a tea crop in Florida. The lower levels of knowledge represent an opportunity for the research team to provide educational activities about tea production. The respondents indicated they had the greatest intentions to learn more about tea production, marketing venues for tea, and tea agritourism opportunities. Thus, these are potential topics on which the research team may focus future educational activities. The Tea Crop Field Day survey respondents retrospectively reported an increase in knowledge from before to after the field day for all five of the given knowledge statements, with a statistically significant increase in the before and after mean scores for the following four statements: (a) I know what kind of pest and disease problems I could expect to see if I grow tea plants, (b) I know several possible approaches for weed management in a tea planting, (c) I can describe potential trade-offs between living and non-living mulches for tea plants, and (d) I know what attributes to look for in shade trees for tea production. There was a small effect size present for the statement I understand the basic requirements of tea plants, which corresponded with the knowledge area respondents were most confident about before the event. Overall, the respondents reported an increase in knowledge from before (M = 2.57; SD = 1.18) to after (M = 3.28; SD = 1.20) participating in the field day. The knowledge increase is considered statistically significant (p = .033, t(30) = -2.24) with a medium effect size (Cohen’s d = 0.63). The respondents also retrospectively reported a positive attitude increase from before to after the Tea Crop Field Day for each of six given attitude statements. There was a statistically significant positive increase in the respondents’ attitudes for the following five statements: (a) I can see myself growing/teaching about tea, (b) I believe tea could be a viable landscape plant for my state, (c) I believe tea could be a viable specialty crop for my state, (d) I feel confident that I could grow/teach tea, and (e) It is worth my time to explore tea as a viable specialty crop. The statement I feel confident that I could grow/teach tea had a large effect size, whereas the remaining five statements had a medium effect size. The survey respondents agree with all four of the intention statements: (a) I am interested in learning more about tea production, (b) I am interested in learning about marketing venues for tea, (c) I am interested in learning about agritourism opportunities with tea cultivation, and (d) I intend to grow/teach tea. These findings support the previous recommendation to increase the number of educational activities for current and potential tea growers focused specifically in tea production, marketing venues for tea, and tea agritourism opportunities.
- Tea Research Project (Webinar)