Progress 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 consumer 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.
- - Producer
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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. Shade tree type (moringa vs. persimmon) was the whole plot factor, ground cover (rhizoma peanut vs. cowpea-crimson clover rotation) was the subplot factor, and tea variety (three) was the sub-sub plot factor in three replications. Each plot consists of six plants of each variety, for a total of 216 plants 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. Cover crop subplots consist of alternating 3-row strips. 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. 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. The Fairhope plants were field-grown from seed and provided by Donnie Barrett at Fairhope Tea Plantation. The Large Leaf and Red Leaf plants were purchased from Cam-Too in Greensboro, NC.
1. Impacts of cover-and-shade systems on tea growth, physiology, yield, and quality. Tea plant growth will be tracked with stem caliper measurements and pruned biomass. Physiological functions will be assessed once every three months, beginning in the second year of the study. PSII efficiency will be measured through the use of OJIP analysis of chlorophyll fluorescence, and chlorophyll content will be measured using spectrophotometry. Tea leaf quality is highly correlated with polyphenols, and will be assessed by measuring polyphenol and caffeine concentrations in made tea (28, 29). We will quantify key antioxidant polyphenolics (epigallocatechin gallate, epigallocatechin, epicatechin gallate and/or epicatechin) in tea prepared from processed green tea leaves using HPLC-mass spectrometry methods. The timing of quality analyses will be determined by plant growth; these analyses will be conducted as soon as sufficient material may be harvested from the plants, likely during the second or third growing season.
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, these analyses may not be 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 will be assessed within each growing system. Percent cover for weeds versus cover crop will be assessed within quadrats (30 cm x 30 cm square) placed adjacent to tea plants within rows. Quadrats will be photographed from above, and images will be 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 will be collected at one and two years after planting. Segments of the microbial communities will be assessed in each treatment by enumeration of an array of specific prokaryotic genes involved in nutrient cycling via quantitative PCR (qPCR). Examples of genes to be studied include genes involved in the nitrogen cycle, such as nifH (involved in nitrogen fixation), amoA (Bacterial and Archaeal genes involved in nitrification), nirK/S (genes involved in denitrification), and genes encoding phosphatases, such as phoA, phoX, and phoD. Selected samples will also be evaluated for microbial biomass carbon, nitrogen, and phosphorus, and will be screened for the presence of additional genes related to aromatic metabolism, such as those encoding aromatic mono- and dioxygeneases and catechol dioxygenases.
4. Disease incidence and pathogen ecology. Disease incidence and severity will be monitored in all plots throughout the study for comparison among growing systems and site locations. Based on preliminary studies, anthracnose (brown blight), caused by Colletotrichum camelliae, is expected to be the predominant disease problem (30). Isolates of Colletotrichum from symptomatic tissues will be identified based on morphology and DNA sequencing (database comparisons using the ITS, ACT, TUB2, and ApMat gene regions) to monitor for additional pathogenic species. If previously undocumented pathogens are found, including additional Colletotrichum species not yet documented on tea, isolates will be tested to confirm pathogenicity on tea, and first reports will be published. In order to predict potential impacts of pathogen movement within the growing system (farm-level, among crops and between crops and landscape plants), pathogenic isolates will undergo phylogenetic analysis to determine likely host overlaps, and will be tested on related potential hosts; these may include ornamental camellia (C. japonica) and blueberry (Vaccinium corymbosum), and the common native plant sparkleberry (V. arboreum). Additionally, root samples from asymptomatic plants will be 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 will conduct bench studies to examine survival of Colletotrichum isolates on cover crop residues from each growing system, and mesh 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 will be 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 will be removed and plated on a semi-selective medium for isolation of Colletotrichum spp. (31) at 0, 7, and 14 days, and then at 30 day intervals from time of inoculation, until no Colletotrichum is recovered at two subsequent samplings. This experiment will be repeated in March, July, and November, to capture changing litter composition and environmental conditions. For mesh bag studies, infected leaves will be collected from field plants and placed in mesh bags on the soil surface, beneath cover crop standing biomass and litter. Bags will be removed at 30 day intervals, and the leaf tissue will be plated on semi-selective media for recovery of Colletotrichum. Initiation of this study will be timed to coincide with high levels of disease incidence observed in the field, expected to occur in late summer.
5. Tea varietal assessment. Varieties included in the study will be compared for survival, growth (as caliper size and biomass production), and disease incidence and severity. In order to examine suitability of available tea varieties across a range of Florida growing regions, tea plants placed in common garden plots will be assessed annually for survival, growth, and any disease or pest issues noted by the partner grower.
6. Hands-on training in service of growers and students. We will utilize the 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 will 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 will deliver 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-discipline 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 will 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 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 also established successfully, 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 also completely covered the young tea plants, and vined up the shade trees, nearly smothering them as well. Cowpea will be replaced in the spring 2020 rotation plots, tentatively with alyce-clover.
Tea plants at the end of their first growing season are still too small to harvest, and stem diameter differences (caliper measurements) this early may still be biased by differences in initial planting material. However, significant differences were evident in both survival and biomass production. At the High Springs site, Large Leaf plants had higher survival and greater pruned biomass than both Fairhope and Redleaf (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 Redleaf (P<0.01), and Fairhope produced greater biomass than Redleaf (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). Based on results from an earlier study (manuscript in preparation), pruned biomass may be a useful early predictor of yield.
Objective 2. Due to the determination that the cowpea cover is unsuitable for the production system (described above), weed cover analyses were not conducted for the first growing season. Cowpea suppressed weeds exceptionally well, but also suppressed tea plant growth and inhibited plant monitoring activities.
Objective 3. Soil samples have been collected and frozen for analysis. These analyses will be conducted after two complete growing seasons.
Objective 4. Disease incidence was low at both sites during the first season, and no new pathogens were described from either site. 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 analysis will be conducted to properly place the isolate taxonomically prior to submitting a Disease Note for publication. Pathogen survival and host range studies will commence during the second year.
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 designed a research proposal for examination of nitrogen application rates in multiple tea varieties for yield and quality optimization. A future project course is expected to implement the trial.
Educational & Outreach Activities
Field days will be planned beginning in the second year of the project. 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.