Cultivation of Organic Tea in Missouri, With Focus On Low-Cost Overwintering Methods

Progress report for FNC20-1250

Project Type: Farmer/Rancher
Funds awarded in 2020: $8,995.00
Projected End Date: 01/31/2022
Grant Recipient: Scott's Baked Goods
Region: North Central
State: Missouri
Project Coordinator:
Drew Scott
Scott's Baked Goods
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Project Information

Description of operation:

The project site is an urban agricultural space in a residential neighborhood, immediately outside the boundaries of the City of Columbia, Missouri. The site is adjacent to a two-story residence with an unfinished basement which is exposed only at the rear of the house. The previous site of the project organizer's bakery kitchen, the basement, includes a large, three-compartment dish sink, and is painted and coved as if for restaurant work. As such, it now makes an ideal workshop for gardening projects. It opens onto a backyard which is partially below the ground level of the hill into which the house is built, between two retaining walls, where a large container garden can be covered with a canopy for overwintering, and therefore exists all-year-round. Many of the usual US-garden suspects are grown there, including tomatoes, peppers and herbs, as well as clovers used for nitrogen capture, and milkweed, to attract butterflies. The growing medium used in the containers has been recycled continuously since 2005 by composting in large, above-ground bins, and has expanded each year to reach a current volume of 1000 gallons. The compost consumes the entire food-waste output of the house, of the organizer's current bakery kitchen, and of the coffee shop next door to the bakery, as well as seasonal input from a local garden center owned by one of the project advisors, and from a neighborhood barn where a pair of horsed is housed. The garden has been operated since the first years of its existence with sustainability in mind, and today every input and method is organic, and most are OMRI-certified.

Summary:

Tea (camellia sinensis) is a tree crop cultivated at commercial scale almost-exclusively in tropical and subtropical climates, as it is damaged by hard freezes and more-profitable when it may be harvested year-round. In cultivation, the tree is pruned to a height of four to six feet and a proportionate diameter for ease of harvesting, such that many trees can be grown in tight rows when planted in the ground. This standard size is similar to what might be achieved by growing tea plants in large containers, which could be arranged as necessary during overwintering, in order to grow tea in a temperate climate. Scott's Baked Goods, of Columbia, Missouri, proposes to demonstrate the feasibility of this by cultivating and overwintering tea plants in containers. These plants will be added to the existing year-round urban agricultural area, under the scope of the company organic certification, the cost of the experiment arising principally from the expansion of the existing overwintering space; the proving of low-cost, low-impact overwintering methods; and the demonstration, to others, of the profitability of tea cultivation as a local prospect.

Project Objectives:

- Meet the project's increasingly-critical need for an inexpensive, ecologically-sound, high-drainage potting medium by producing, crushing and sifting biochar on the scale of hundreds of gallons. Improve the efficiency of the method in use by powering the sifting process and adding a second barrel kiln.

- Fully-develop current methods of pH correction and nutrient charging of biochar for agricultural use. Prepare coarse product by treatment in a fluidized-bed bioreactor, for use in potting media; and prepare fine product by aerobic composting, for use in soil regeneration.

- Demonstrate grow-out of camellia sinensis plants through several transplantations, up to industry-standard volume.

- Continue to optimize seasonal overwintering shelter using minimal electric mains power.

- Produce a crop of tea leaves, and successfully prepare them for use.

- Instruct interested parties, especially fellow vendors from Columbia Farmers’ Market, in the methods used, with emphasis on business ventures associated with that venue, and establishment of new ventures suited to it.

Research

Materials and methods:

PROJECT PROPOSAL

Without dedicating a building to the purpose, overwintering of tea in Missouri must be achieved with a temporary shelter. The coordinator’s experience in this stems from maintenance of an urban agricultural space, which is partially below ground level and can be covered to create an overwintering area. This is accomplished with a framework of poles that support a fifty-foot double layer of plastic sheet stretching between the permanent retaining walls that define the space. A compost sheltered inside the space, and kept active, contributes substantial heat at no cost, as does solar electric power. Only a fraction of the available space has been covered for overwintering, in the past, and the project aims to enclose the entire space by adding additional structures to support a larger canopy. Mulch, and a great many donated burlap coffee bags, will be used for insulation; and many food-grade plastic buckets donated by local bakeries will be used as grow-out containers for tea plants which the added space will accommodate.

 

TEA PLANTS, 2020

The four-hundred tea seeds purchased for the 2020 season did not sprout. Onomea Tea, a plantation in Hawaii, was to have been the principal advisor to the project, and would have guided the organizer through the germination process. Onomea closed for business permanently during the period between the submission of the project proposal and the project's approval, and staff were no longer available to advise when the seeds were planted. As such, germination was attempted by a method (seeds4_13 (hawaii.edu)) published by Hawaii University's College of Tropical Agriculture and Human Resources (CTAHR), but this was not successful.

Forty-nine tea seedlings were purchased to replace the sprouts that did not grow. They were received at 24" tall, rooted in one-quart packages, and transplanted into two-gallon buckets. A growing medium for tea plants must have low water retention and a pH between 4.5 and 5.0 - easily low enough to kill most garden plants - and composing such a medium was challenging. Samples of prospective ingredients were combined with water purified by reverse osmosis (RO water), and the pH values of the resulting solutions tested to determine the probable effect of each material on the pH of a planting medium. The solutions were mixed at 200 F in glass jars, which were sealed, agitated, and left to rest for four hours, before pH measurements were taken three times in sequential rounds, and the average values recorded. The medium finally composed for the project plants consisted of the following elements, by volume, largely because the project had them available:

25% purchased compost, sifted to remove particles smaller than peas or larger than grapes - average pH 6.99

25% mulch fines, sifted from bulk mulch to remove particles larger than peas (not expected to decompose much further) - average pH 7.05

15% coconut coir, as measured when moistened and fluffed (after purchase as a compressed block, completely dry) - known to be pH neutral

15% dry peat moss, sifted to remove fines and large chunks - average pH 5.87

10% lava rock, sifted to remove pieces smaller than grapes or larger than ping-pong balls - known to be pH-neutral

10% perlite, half-centimeter grade - known to be pH-neutral

The entire bulk of the medium produced was moistened before planting with a solution of RO water and citric acid, an organic acid used commonly as a food additive and intended to reduce the starting pH of the medium, then mixed thoroughly to ensure uniformity. The moistening solution was measured at a pH of 4.8 before application. The plants responded well to transplantation, and continue to grow.

The tea plants have demonstrated slow growth, as expected of any species of tree; profound resistance to drought, going several weeks without watering; and no ill effect from any degree or duration of sun exposure. They are also sturdier, physically, than most garden plants, and have shown no susceptibility to damage by high wind, heavy rain, or extended periods of cold and damp. They have, so far, shown no sign of disease, but do seem to be susceptible to an unidentified species of scale insect, which causes no quantifiable damage. The specimens under the care of the project have not been exposed to an air temperature below freezing, but it is not expected that they would survive. The plants have at times shown minor sensitivity to overwatering and lack of light, during overwintering, and the three plants lost during overwintering are believed to have died from some combination of these factors.

 

2020 OVERWINTERING SPACE - CONSTRUCTION

The proposed structure was built successfully at a total cost of $1205 in hardware provided by SARE and an additional $200 in wire and plastic sheet purchased separately. The outline of the space is very similar to the original design, but the arrangement of the interior was changed several times to accommodate the evolving project, most-notably to change the shape of the roof. The original design would have used twenty-one-foot stock lengths of square aluminum tube in pairs which met at the peak of the roof and sloped downward to the East and West. At the advice of project advisor Charles Bay, this design was changed so that the roof of the structure sloped downward from South to North in a single span of twenty-one feet. This design presented much less surface area to the seasonal track of the sun across the sky, but increased the slope of the roof to better shed rain, leaves, snow and meltwater. For these purposes Mr. Bay recommended that the pitch of the roof be no less than 1:2, and the north wall of the structure was moved inward by six feet to achieve this. Each of the canopy supports would have connected to one of the T-posts that define the north north wall of the enclosure, but instead the posts for the new design were added to the posts already driven for the old design to make two rows, so that each of the roof supports could be connected to two posts. This strengthened the canopy at the cost of lowering the north edge of the roof to less than five feet, leaving a six-foot void space between the inner and outer rows wherein the canopy was too low to place container platforms. Shipping pallets were secured to each of the inner posts as supports for plastic sheet which was used to encapsulate the void space fully. This was intended to prevent heat loss through the north wall due to wind, as the north wall is the only vertical surface of the enclosure above ground level.

 

MULCH AS INSULATORY GROUNDCOVER

The twelve cubic yards of mulch provided for in the project budget were piled manually, in 114 wheelbarrow loads, against the outer surfaces of the retaining walls that form the east and west boundaries of the overwintering shelter which accounted for about half of the total labor of building the enclosure. It was applied in piles which reach two-feet-deep at the outermost ends of the retaining walls, where the existing ground level was lowest, and extended along the walls to wrap around the foot of the house on each side. The retaining walls are contiguous extensions of the foundation walls of the house, made of a dense concrete that conducts heat effectively. The mulch was intended to cover as much of the exposed faces as possible, to prevent convective loss of heat from the atmosphere inside the shelter. Once covered, the deep-rooted walls were also expected to become conductive channels of deep-ground heat into the structure.

 

CLIMATE CONTROL IN THE 2020 OVERWINTERING SPACE

Wireless IP sensors for measuring temperature and humidity were set up in the basement before the outdoor canopy was completed, where they were used to monitor the closed bays in which seeds were germinated. They provided comprehensive data via an easy-to-use cellphone application for as long as their original batteries lasted, but later presented difficulties. The sensors were designed to be accessible from anywhere by internet, but were never reliably accessible on any device not connected to the same local Wi-Fi network as the sensors themselves, preventing remote monitoring of the shelter by anyone not at the project site. Possibly for this reason, the expected alerts were not received through the app when the batteries in the units began to die. When the sensors stopped returning data, the batteries in each were replaced, but afterward they were no longer recognized as functional in the application, which stopped returning data altogether. This seems to have been a glitch in the software, and took a great deal of time to resolve despite ready and willing assistance from the supplier. As such, comprehensive measurements of atmospheric data could not be collected during the 2020 overwintering period.

All container plants were moved into the basement of the residence adjacent to the outdoor enclosure at the end of the natural growing season, to clear the way for the building of the enclosure itself. Electric space heaters were used to hold the temperature of the basement at seventy-five degrees, about seven degrees warmer than the upper floors of the house. The power drawn by the heaters peaked at eighteen kilowatt-hours per day at a thirty-percent duty cycle, but completion of the canopy enclosed the only exterior wall of the basement entirely, and once the temperature within the outdoor space stabilized, the duty cycle of the heaters dropped to less than ten percent. The single window in the exterior wall was opened by removing the sashes completely and covering the opening with sheer fabric to allow gas exchange between the two areas while preventing ingress of insects and debris, and to allow some amount of warm air to bleed from the house into the outdoor enclosure in the event of severe heat loss, but this did not occur.

Samples of the composted growing medium produced at the project site are submitted for nutrient testing, and the results inform the use of compost tea made to feed container plants. When the project began, compost tea was still being made at the project site by combining mature compost with RO water in buckets, then pouring the contents of the buckets through a sieve. Experimentation with the use of a freshwater aquarium to increase humidity inside the enclosure led to establishment of a bioreactor which serves both purposes. Solid organic waste material, called "mulm," that accumulates in freshwater aquaria is reliably rich in nitrifying bacteria, and mulm drawn from the existing aquarium was mixed with fifty gallons of RO water in a seventy-five gallon glass tank with a substrate of fine sand and biochar, and fed with small quantities of dry alfalfa, wheat bran, and compost for several weeks to establish a robust bacterial culture. Feeding of the heated, aerated tank has continued to generate nutrient-rich water for fertilization of project plants, and leaving it open to the air has maintained humidity within the enclosure at an acceptable level.

 

ANIMAL CONTROL IN THE 2020 OVERWINTERING SPACE

The project site is visited by deer and every kind of small mammal native to Missouri, as well as neighborhood pets. Gardening efforts beginning in 2005 have shown that deer do not enter certain areas near the house; this, as well as the poor, clay-heavy soil left behind after commercial scraping of the pre-existing topsoil by the original developers of the property, were the reasons for the original shift from in-ground gardening at the site to container gardening, which allows plants to be grown in areas not trafficked by deer, regardless of soil quality; and for even mature plants to be moved. The project has so far avoided intrusion by deer for this reason, but a number of tomato and pepper seedlings left on low shelves were destroyed by rabbits during the spring. Rabbits were observed in real time, from vantages overlooking the growing space, to be unwilling to eat from any plant on a platform at least two feet off the ground, despite having, presumably, the ability to reach them by jumping. No such plant was attacked by rabbits during 2020 - possibly due to an instinct to avoid notice by predators which makes the rabbits unwilling to leave the ground. Following this observation, all container platforms were raised to a height of three feet, and no further damage by rabbits has occurred.

The original platforms for the container plants were sturdy wooden shipping pallets, supported at each corner by stacked cinder blocks. Advisor Charles Bay has used identical platforms for many years to hold plants for retail sale at Wilson’s, his Columbia, MO garden center, and suggested the method by example. But these began to collapse under the weight of the container plants in a matter of months with repeated exposure to rain and high humidity, because the two-to-five-gallon containers in which the plants at the site were grown to full maturity were so much heavier than the starts packaged for transport at Wilson’s. When a quantity of seven-foot steel I-beams became available to the project for $10 apiece locally, second-hand, twenty of these were purchased to replace the collapsing wooden pallets, and there have been no further collapses. The heaviest of the wooden pallets with which the project began have also continued to serve as container platforms, as have several that were braced with 4x4 timbers. The I-beams continue to be checked regularly for signs of rusting, but these are minimal, so far.

 

PEST CONTROL IN THE 2020 OVERWINTERING SPACE

Aphids began to multiply in the overwintering space shortly after the container plants were moved in, presumably as a result of the lack of predatory insects or other biological counterbalances inside the enclosure. Daily manual removal was eventually necessary to prevent lethal damage to the affected plants. This could be accomplished effectively with a handheld spray bottle, but not by the organizer alone. Because the COVID-19 outbreak had begun by this time, additional hands were not invited to assist in removing aphids. Instead, three alternative methods of organic pest control were attempted. First, powdered diatomaceous earth was scattered over test plants and the soil surfaces in the containers, but did not harm the aphids. Second, a detergent solution was used to wash test plants by turning the containers on their sides and spraying the solution so that it did not drip into the soil.  The detergent was left for twenty minutes before being rinsed off thoroughly with RO water, but seemed no more harmful to the aphids than rinsing with water, and did harm the plants, which lost leaves and developed a degree of chlorotic mottling. Finally, one-hundred-fifty adult ladybugs were purchased and released into the space, but did not have an observable effect on the aphid population, and were no longer present two weeks after release. The reason for this is not clear, as the space remained closed during this time and no great number of dead insects was found despite a search, but the provider of the ladybugs suggested that they may have received too little water, which in the wild they require daily in the form of rain or dew, and which was provided by the project twice per week in the form of RO water sprayed liberally onto the plants.

 

BIOCHAR AS IDEAL POTTING MEDIUM

The planting medium produced at the project site and used for most container plants is about fifty-percent peat moss by volume - the pure material retains water more-effectively than a kitchen sponge, and must be amended for plants that require greater drainage. The transplantation of tea plants during 2020 consumed the project's entire supplies of lava rock and perlite, making clear the need for additional suitable material. Later in the season, when eight lemon trees were transplanted from five-gallon into twenty-five-gallon containers, the only amendment initially available in the needed volume was woodchips, sifted from the mulch purchased as groundcover. The same woodchips had been part of the medium in which the trees were first planted, in 2018, but by 2020 their decomposition had begun to consume the nitrogen in the soil, causing the lemon trees to show signs of deficiency. This was determined by advisor Charles Bay, who recommended that they not be used again.

In pursuit of a more cost-effective, ecologically-sound alternative to purchasing a great deal more lava rock or perlite, an effort was made to convert a small quantity of woodchips into biochar using equipment on-hand. This was successful, but not efficient enough to create the needed volume, and a fifty-gallon, stainless-steel shipping drum was purchased (second-hand; twenty dollars) for use as a "char barrel," a sort of low-temperature kiln for producing biochar. This came from a reseller from a nearby town, with experience selling the drums to University of Missouri agriculture students for the same purpose. At his advice the interior of the drum was lined with stacked fire bricks to provide thermal mass and protect the drum itself from a kind of corrosion which occurs eventually, even in stainless steel, with repeated exposure to wood fires. Coincidentally, the City of Columbia ordered the felling of a great many decades-old trees growing along the path of a powerline near the project site not long afterward, and allowed the project organizer to retrieve as much of the cut timber as possible before the rest was collected by a city mulching crew. Thousands of pounds of this timber were brought to the project site at no cost and prepared by the project organizer by manual splitting, as if for firewood.

A biomass becomes charcoal in a self-sustaining exothermic process called pyrolysis when heated to the temperature at which it would burn, but in the absence of oxygen, releasing steam and other gasses which tend to stall the process if they do not escape. Charcoal produced for agricultural use from materials consistent with such purposes is called biochar, typically a jet-black, brittle substance consisting almost-entirely of carbon, and smelling strongly of wood smoke. As produced in common practice, it typically occurs mixed with residues of the combustion gasses produced during pyrolysis, and some quantity of ash. Using the drum arrangement described, the project converted eight full-drum batches of the prepared wood into biochar, by building energetic wood fires in the bottom of the drum, filling as much of the empty space with wood as possible without smothering the fire, and then capping the drum once all of the fuel had ignited, leaving only a small gap through which exhaust gasses could escape. The pyrolytic reaction typically continued for three to six hours, after which it stopped producing exhaust gasses, the lid was closed completely, and the drum was left to cool overnight.

The resulting biochar remained mostly in large chunks, still in the shape of logs and branches. These were brittle-enough to be reduced, by crushing underfoot in large tubs, to a grade of particles between half-an-inch- and two-inches-wide, but resilient-enough to do so without reducing more than thirty-percent by weight of the bulk material to finer particles. This coarse fraction of the biochar was rinsed with hot tap water to remove fine particles and traces of ash, then flushed with RO water, and finally soaked in RO water to prepare it for use as a soil amendment. Sources consulted before using the biochar agreed that the material would have a basic effect on the pH of a solution to which it was added, and possibly a very-basic effect. But experimentation showed that this was only conditionally-true of the material produced by the project. Fifty-gram samples of the coarse fraction produced as a soil amendment; a fine fraction consisting of material retained on a 2mm sieve, and a dust fraction consisting of material which passed through it; were each combined with 300 grams of RO water in glass jars, and these were sealed and left to rest at room temperature without exposure to light. The resulting solutions were agitated and tested for pH at 0, 1, 2, 5, 17, 46, 68 and 96 hours. The results showed that the pH of each solution fluctuated substantially during the period of observation; that all three trended over time toward neutral pH values; and that the solution produced with the coarse fraction of the biochar in fact remained mildly-acidic at all times. Only the solution made with the dust fraction remained basic at the end of the experiment, possibly because the dust fraction contained all of the finest material sifted from the bulk product, which would have included nearly all of what ash was retained.

 

2020 SOLAR APPLICATIONS

Applications of solar hardware to the project have not yet been addressed due to lack of manpower available as a result of the 2020-21 COVID-19 pandemic. No expenses for related hardware have been incurred, however those applications have continued to be examined and reevaluated in light of new information. As such, the budget for solar hardware has been rewritten to account for a new deployment scheme, which, if approved, will begin following the second distribution of SARE funds.

Research results and discussion:

RESULTS - TEA PLANTS, 2020

The complete failure of the original tea seeds to germinate was a profound blow to project morale, and the reason for the failure of the documented method has not been determined. But the purchase of tea plants to replace the anticipated sprouts required a significant course change, one that incurred the need for a massive volume of potting medium far ahead of the original schedule, which motivated the investigation into sustainable materials that led ultimately to the production of biochar which the project has undertaken. The occasions on which the project has succeeded in using what would have been waste materials - thousands of pounds of wood used to make biochar, hundreds of buckets used as planters, hundreds of burlap coffee bags used as insulation, and hundreds of pounds of coffee grounds added to the compost - are the occasions on which the project has the greatest success as a SARE initiative, and the aspects of the project of which the organizers are the most proud. Production and successful application of biochar seem likely to be of critical importance to the ultimate success of the project in cultivating tea, as well, as the budget could not have been amended to cover the direct purchase of an alternative material, and no more-sustainable alternative is known by the organizers to exist. Budget changes have been proposed, at the time of this report, to cover the purchase of small numbers of fresh seeds from each of three new sources, intended for further attempts at germination. If successful, these will leave the project with far more plants to care for, and in even-greater need of media, a problem the organizers are eager to have.

Environments in which tea plants occur naturally are tropical or subtropical, with routine rainfall, and soils that show substantial drainage and little pH buffering capacity. These soils trend toward extreme acidity over time, as the slight natural acidity of each rainfall neutralizes and washes away a little more of what alkaline constituents the soils do contain. Because this geologic process takes years, the project tea-potting medium was treated with citric acid when first blended to bring the pH into the 4.5 - 5.0 range. Following potting, the first several waterings were with solutions of citric acid, and later apple-cider vinegar, mixed to pH values in the same range with the expectation that this would maintain stable soil acidity. It was quickly realized that watering with only enough of these solutions to wet the soil, and not enough to flush it - such that at least some water flowed out of the container - would have the effect of adding acidifying solute to the soil with every application, and that this would likely cause the pH to drop over time. Afterward the plants were watered with RO water only, for several weeks, which has a precisely-neutral pH of 7.0. This avoids the alkaline effect that the hard local tap water would have on the soil, but does not effectively simulate natural rainfall, which attains its acidic character through aeration with atmospheric CO2.

The plants have continued to be watered with solutions of RO water, mixed with citric acid or vinegar to a pH of 5.8, consistent with ordinary rainwater, but a fully-satisfactory method of maintaining the acidity of the growing medium has not been found. The coarseness and low water retention of the medium in which the tea plants grow makes in situ pH testing of the medium unreliable as performed with the digital probe used for all other project applications. The probe measures acidity by applying an infinitesimal electrical current to a material, and the results returned may vary widely when the coarseness of a tested material is too great to reliably establish a current path between the two electrical contacts on the surface of the probe shell, or when the medium contains very little moisture. The pH of any growing medium is more-accurately described as the pH at which the water that it retains (the soil solution) stabilizes when the medium is wet, and it can be assessed by measuring the pH of effluent water, but taking measurements in this way would require a degree of waterlogging that tea plants are not expected to tolerate, and also have the effect of washing away soil nutrients.

Addressing this problem is currently a primary goal of the project. The next experiment will use the biochar produced at the project site in the application of a hydroponic principle to which the tea plants are expected to be suited, counterintuitively, as a result of their drought tolerance. Pretreated, coarse biochar will be used to compose a growing medium with even greater drainage than the medium in use, because it does not need to maintain high fertility and can therefore have lower biomass content. The settled, wetted medium will still contain enough air space that waterlogging is impossible. Test plants grown in it will be flushed fully several times per day to maintain moisture, and the runoff collected in a container, to be used again with each watering and topped-off with RO water as needed, essentially extending the soil solution out of the soil mass and into an accessible reservoir. The runoff from each planter will therefore remain strongly-representative of the actual soil-solution pH, allowing accurate measurement moment by moment, as well as adjustment and fertilization by amending the solution in the reservoir. If successful, the arrangement will also facilitate automated watering, which the project plans to attempt, to address the risk of full dehydration of the growing media following missed waterings. However, the plants' documented tolerance of dry conditions is reason to expect resilience even in the event of such a failure.

 

RESULTS - 2020 OVERWINTERING SPACE

The effectiveness of the double wall at preventing heat loss due to wind could not be characterized once it was realized that the structure also had the effect of channeling ground heat into the enclosure. The width and volume of the wall cause it to insulate the earth beneath it in a broad arc, proportional to the wall itself, effectively recruiting the material of the ground as insulation between the soil under the canopy, which is kept warmer by the enclosure, and the colder soil outside it. The same effect can be accomplished by digging a trench deeper than the local frost line around a greenhouse and filling it with insulatory material, which isolates the surface soil inside the trench from the surface soil outside it, preventing the loss of ground heat to the surrounding soil and effectively heating the greenhouse geothermally. This method was decided against because of the labor and soil disturbance it would have incurred, but it was not anticipated by the project that the void wall would also have the effect of including the earth beneath the canopy in the thermal mass of the enclosure in the manner of a geothermal trench. No one involved with the project was previously familiar with this method of accomplishing the effect. If it was the first time that such a void wall has been made for this purpose, then the project has coined the term “void wall.” Future enclosures will experiment with wider versions and make direct measurements of ground temperature.

Energetic gusts of wind have loosened parts of the canopy on several occasions since its completion, and these were pulled tight and weighed-down at the edges with additional masses, mostly square blocks of concrete averaging 150 lbs. These blocks were sections cut from the floor of a Columbia business as part of a plumbing project, and saved at no cost by the project organizer for this purpose. Additional securement weights included large trunk sections from trees cut down by city maintenance crews and collected by the project organizer, also at no cost, for conversion to biochar; wood collected in this way was cut into sections by chainsaw for charring, but specimens proving to be maple were so hard that they were prohibitively difficult to section, and were kept for securement of the canopy instead.

 

RESULTS - CLIMATE CONTROL IN THE 2020 OVERWINTERING SPACE

Without the use of the needed sensors, atmospheric data could not be collected as-planned, but the environment of the enclosure has remained consistently above 70 F, and no plants have been lost to freezing.

The bioreactor tank seemed to have the intended effect, but no humidity data are available. The tank has been consistently maintained at 76 F and aerated constantly with an aquarium pump, and loses about one gallon of water per day to evaporation, which is replaced weekly with RO water. Small quantities of alfalfa, bran and mature compost are added twice per week, and the tank water is stirred and skimmed with a 1mm sieve to remove coarse material. This material, once drained, is light, and has little nutrient content, therefore it is saved for use as a germination medium, for which purpose it is sometimes sterilized by baking. The water in the tank is essentially a compost tea, rich in nitrate and minerals, and watering plants with it has been a reliable way to nourish potted specimens that would otherwise exhaust the nutrients in their containers. 

 

RESULTS - MULCH AS INSULATORY GROUNDCOVER

In addition to the greatest single labor which the project has so far involved, this measure was likely the greatest contribution to the overwintering capacity of the agricultural space, and one which will continue to benefit for years to come. Additionally, fractions of different coarseness sifted from the mulch proved to have various uses not previously considered: the coarsest material can be converted easily into biochar; the finest material decomposes quickly in compost, contributing substantial bulk (and, in fact, makes excellent cat litter); particles on the small end of intermediate size can be combined with large quantities of too-wet material such as fresh coffee grounds to produce a mixture suited to composting; and larger intermediate particles can be used to mulch in areas where a heavy runoff of rainwater hits the ground, which require protection from erosion but also quick drainage. Separation of grades of mulch by manual sifting requires too much time and effort to be practical for most applications, but project operators hope to develop a quicker and less-laborious method of sifting both soil and mulch, which may allow such fractions to be produced for these and other uses.

 

RESULTS - ANIMAL CONTROL IN THE OVERWINTERING SPACE

For the sake of experiment, two-dozen tea plants were moved to an area frequented by deer and rabbits and left on the ground for a period of one month during the natural growing season, to see if they would be attacked. None of these plants suffered observable damage from any creature during that period, which the project presents as evidence that tea plants are not recognized as food items by rabbits, deer, or any other herbivorous animal present in the woods of Columbia, Missouri as of summer 2020.

The project has identified but not observed a need to harden the overwintering enclosure against determined intrusion by animals. This is limited by the hermetic nature of the canopy, but scavengers with keen-enough olfactory senses to detect food wastes in the active composting bins, even when the canopy is closed fully, include raccoons, possums, mice and neighborhood dogs, and any of these could damage the enclosure such that it would no longer hold its temperature. No animal damage was observed during 2020, but the frequency with which the compost bins are visited by these creatures during warm weather suggests the possibility. As of 2020, meat and bones are no longer added directly to the compost at the project site, because only these food items have been observed to be removed from the bins by animals, most probably possums. While additional fencing could prevent intrusion by dogs, the project has not yet established a practical method of protecting the canopy against determined entry by all scavengers.

 

RESULTS - PEST CONTROL IN THE 2020 OVERWINTERING SPACE

The cumulative damage of predation by aphids ultimately killed all of the softer plants - every specimen of tomato, all but one species of pepper, and every herb other than rosemary. But lemon trees, coffee plants, rosemary shrubs, and tea plants suffered no damage. Following the deaths of the last susceptible plants, the aphid population in the overwintering space died out, presumably due to starvation, and did not reestablish itself even after all efforts to remove the aphids ended. Thus, the months-long period during which the aphids were present, in close proximity to the tea plants and others, demonstrated that the surviving plants were not susceptible to aphid attack, even when exposed to a large population in a closed environment with nowhere to go. Thus, the project seems to have demonstrated the invulnerability of tea plants to aphids - likely the most destructive pest in American agriculture.

The tea plants have been observed to be susceptible to a species of scale insect present in the growing space which also attacks the lemon trees. But these multiply so slowly that they can be controlled easily by manual removal. It is not clear that this particular scale insect causes substantial damage to any of the plants on which it feeds.

 

RESULTS - BIOCHAR AS LOW-COST POTTING MEDIUM

Sixty gallons of the coarse material were ultimately produced for use in the lemon tree medium, and combined as-planned with compost in a dry volumetric ratio of 2:3. pH tests of the mix have shown no trend toward basicity as of March 2021, and the project operators therefore consider biochar a prime candidate as a planting medium for tea.

As the plants already cultivated at the project site continue to grow, and new plants are added during the natural 2021 growing season, the project anticipates a great and increasing need for a suitable growing medium. Because tea requires an extremely-low pH, the project intends to experiment further with pre-treatment of biochar to determine any effect it might have on the pH value of solutions which begin not as neutral but as highly-acidic; and any initial sequestration of nutrients that it may cause as a result of the high cation-exchange capacity that results from the material’s extreme ratio of surface area to volume. Production of a biochar-based planting medium made for tea plants - a lightweight, high-drainage, inexpensive medium which can be produced easily on-site, and from waste inputs - may become an ideal method of cultivation, one which also sequesters huge masses of carbon permanently, and incurs little direct fiscal cost or ecological impact. As of Q1 2021, the project is preparing to expand the application of the principal at play in the aquarium tank already in-use as a humidifier and fertilizer vat - effectively a fluidized bed bioreactor - to pretreatment of coarse biochar for use as a potting-medium amendment. A tertiary goal is the incorporation of the wood ash and fine particles of biochar which occur as by-products of the pyrolytic process into a nutrient-rich composted medium made with bakery and restaurant waste, which may be broadcast throughout the neighborhood of the project site to begin regenerating topsoil harvested long ago, when the properties were initially developed.

Participation Summary
1 Farmer participating in research

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Planned outreach exercises were postponed during the COVID19 pandemic as a precautionary measure. The project organizer has already received the first dose of a two-dose vaccine at the time of this report, and will conduct outreach events at a date to-be-determined.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.