Oasis Gardens (O.G) An Experimental Wetland Based Vegetable Production System
Kalu Yala Institute Agriculture + Biology Spring 2017
Created By Brooke Taylor Stephen Langford Lacey Kent-Webber
Overview The intention of this project was to take an overgrown and dilapidated pond on the Kalu Yala Farm and revitalize it by constructing a raised garden bed, inspired by a traditional Aztec agricultural technique known as Chinampas, or “floating gardens.” The idea is that, with a constant water source and a good cycle of nutrients from the plants and fish throughout both the garden bed and the pond, this wetland system will be both selfsustaining and highly productive with consistent yields. In addition, by creating an area on the farm that invites the community into the farm to relax and appreciate their surrounding environment, the Oasis Gardens acts not just as a viable model for how to actually scale out capacity for a full farm to table experience, but also as a source of cultural evolution in that it inspires community members to form an appreciation for where their food comes from. In a way, it is an art that feeds.
Chinampas Chinampas were first used throughout Mesoamerica prior to the rise of the Aztecs. Once Aztecs came to power, their population grew to great numbers, and such a large population meant that more food needed to be grown in order to sustain them. Therefore, the Aztecs began using a series of Chinampas in order to increase food production. These ‘floating gardens’ were created in shallow lakebeds and were roughly 30m x 2.5m rectangular structures. The structures were fenced in by wattle (rods interlaced with twigs/branches) and were then filled with mud and decaying vegetation to provide a healthy soil for the plants. In order to eliminate the risk of drowning the plants, the beds were raised above water level, which ensures a constant water source to the roots, creating a nutrient rich and highly productive soil and a vegetable production system that requires little to no maintenance. Crops that were traditionally grown included maize, beans, squash, amaranth, tomatoes, chili peppers, and flowers. Trees were also sometimes added in corners to help secure the structure. It is not the lack of success that destroyed the chinampas system. As raised, well-watered beds, Chinampas had very high crop yields with up to 7 harvests per year. However, when the Spanish invaded the Aztecs, many of the dams and sluice gates regulating the water flow were destroyed and the Chinampas were deconstructed, intended to never rise again. That said, this practice could theoretically be a viable model of sustainable agriculture.
Multi-Dimensional Design As in good permaculture design, the chinampa plot revolves around turning waste into a resource. It stacks functions to maximize yields and minimize work in a small-scale, intensive system. With such a design, it is not only a self watering system, which is created by wicking in from the sides as moisture is brought to the surface and then evaporated, but it is also highly productive, and mostly self-sustaining. Hypothetically, the garden bed will never have to be watered once the roots have extended down to the environment where soluble nutrients stay suspended and available. With such a complex biodiversity in both the garden plot and the pond, there is a great cycle of nutrients allowing all forms of life within the system to thrive and grow. By understanding the functions of each component, placing each plant and structure in a place that maximizes its use as a resource, the chinampa system is able to maximize productivity and minimize waste. Even the fish (Tilapia) are able to take advantage of the organisms attracted to the plants and becomes a source of food for the fish, which increases the efficiency of the self-maintaining system. Moreover, the Oasis Gardens can be said to go beyond the principles of permaculture as it also embodies the practices guided by regenerative agriculture. It appears to have both successfully revitalized the pond and created a healthy layer of topsoil. This, as part of the greater irrigation system of the Kalu Yala Farm, will now allow for a cycle of nutrients that, in time, will help further develop the Kalu Yala Farm. The garden is not only able to prolong the run-off, utilizing as much water, nutrients, and energy as possible before losing them, but it also serves as a catalyst for the expansion process of the farm by initiating a water and soil catchment system.
Cultural Evolution Homo Sapiens began our estrangement from nature around 10,000 B.C. when huntergatherer societies transitioned to one of agriculture and settlement. Since then, as populations have grown exponentially in numbers and in technologies, agricultural practices, too, have advanced. At the same time, concentrations of people in urban areas have skyrocketed, resulting in a drastic general disassociation with the food production process and even nature as a whole. Current food systems also contribute to multiple practices that are detrimental to our natural environment. However, their remains an affinity for nature built into man’s DNA, the key is just to figure out how to foster that affinity and make it meaningful. Therefore, by creating a space on the farm within eyesight of a path with heavy community foot traffic, the Oasis Gardens invites both individuals and groups, whether for relaxation or recreation, while also helping them form an attachment and appreciation for the system that feeds them. They are able to learn about the system, watching their
food grow, seeing the process, the trials and tribulations. They become more educated and informed and are able to make more conscientious decisions. Then, by also serving as the beginning of an expansion of the farm, the visitors will also get to witness the development of a full farm-to-table system whereby all food and nutrients are produced within one big closed-loop system, just as within the Oasis Gardens. This is an attempt to localize peoples food systems, which is key in a sustainable community. The connection to food must go beyond the farm to table method and create an emotional and mindful connection to the food consumed. It then goes from an experiment in a dilapidated pond to a catalyst for the sustainable development of the entire community.
Construction To say that the construction of the first Kalu Yala Chinampa was labor intensive would be an understatement. Before even beginning to ideate on designs for the structure, we first needed to clear out the pond so that we could really know how much space we were dealing with. To our surprise, it was going to be a much larger project than we expected. However, after clearing out all the grass and weeds that had overtaken the area, we were then able to begin envisioning what this “floating garden� would look like. We played with ideas like dendritic patterns, narrow paths, crenelated shapes, and eventually decided on a wider bed as this design would allow for the highest number of plants able to take advantage of this great nutrient cycling system. We also decided to use bags of sand to form the walls of the chinampa, and to repurpose used airmattresses as liners for the bottom of the pond and the walls of sandbags. From there, the next steps consisted of preparation and then physical construction. We began planting seeds we knew to be water-loving plants in pods in the greenhouse, filling poly sandbags with sand from a beach on the Rio Pacora, and cutting air-mattress no longer functioning down the seam. It was then time to line the bottom of the pond with a few mattresses to ensure water remains in the pond, transport the bags of sand to the pond area, and stack the bags in the pond to ensure maximum stability and resiliency for both rainy and dry seasons. As we are unfortunately unaware of the water level variability between seasons, it was decided that it would also be best to dig a large irrigation ditch
on the other side of the pond that will allow water to flow out whenever when the levels increase to a level that would flood the garden plot. Once both walls were constructed, shade cloth was also applied on top of the liner for aesthetics purposes, as reaching plants can grow across them and give a natural appearance to the wall, as well as contributing to the biodiversity of the wetland system. In addition, branches of balo were propagated in a similar manner along the bank of the entire pond in order for the roots to grow and help serve as a retaining wall.
Soil Building: Use of Biochar With the construction of the walls completed, it was time to begin building up the layers of the garden bed. The base layer consisted of mostly large rocks and clay. Once this was brought up to about 3 inches below the surface of the water, clay and rocks were substituted for organic material in a sheet mulching technique by layering both green and brown mulch, with the goal being to build up a healthy layer of top-soil. With the primary components of the mulch being straw and water-lettuce, soil pockets were then used to transplant the seeds that had been planted several weeks prior and had been filled with a mixture of compost, leaf cutter ant litter, and biochar. Biochar is a soil additive that helps to reduce Co2 emissions into the atmosphere because it resists degradation and sequesters the carbon in soils for thousands of years. The biochar that was used in this chinampas system was created by putting organic matter inside a Top Lit Up Draft (TLUD) biochar processor. This system consists of a steel 55 gallon drum with small air holes in the bottom and a partially opened lid. The processor creates the conditions for pyrolysis of wood into biochar by smothering a short, intense, top lit fire with the cover. The biomass is slowly charred, taking roughly 2 to 6 hours to complete depending on the organic matter that was used. The charcoal produced can then be used in soils that are depleted as it improves water quality and quality of the soil by improving retention of nutrients as well as agrochemical utilization. This ensures that more nutrients will stay in the soil helping reduce risk of pollution. The leaf cutter ant litter was also used in the soil mixture as it is assumed, and can be seen, to have high soil nutrients with an active bacteria and fungi population. This adds richness to the soil and adds to the productivity of the soil and chinampa plot. Compost holds the same characteristics, which makes this soil an ideal mixture for successful vegetation within this experiment.
Vegetation All the vegetation that was planted in the garden bed is edible. All of the plants are annuals with the exception of Malabar Spinach. Malabar Spinach is a perennial green that can be found in tropical climates. It is a productive leafy green vine that can be continuously harvested and thrives in moist lowlands. The annuals that were planted are: bush beans, cucumbers, beets, eggplant, tomatoes, watercress, bibb lettuce and swiss chard. Annuals are ideal to plant in the chinampa system because they thrive in rich soil
and love constant irrigation. Companion planting technique was applied to the design of the vegetation in the garden bed, such as the row of bush beans down the center because lettuce, beets and cucumbers are known to be happy beside them. The addition of beets to the garden bed was fully experimental and was an attempt to see if a root vegetable could thrive in a chinampa system. The success of a beet grown in the garden would fuel the production of root vegetation such as carrots and onions. A salad mixture was thought into the design as well, the combination of harvesting the chard, bibb lettuce, Malabar spinach and watercress together makes for a delicious lunch or dinner. Tomatoes and eggplants are hypothesized to be the most successful in the garden bed because they both enjoy rich soil and deep, well-watered roots. They also enjoy being watered from below up as opposed to overhead watering, this actually stunts the growth of these annuals. The main goal of the vegetation in this garden bed was to create a productive food system and contribute to the fully farm to table goal of Kalu Yala. A row of large golden sunflowers was planted throughout the center of the bed to improve the aesthetic of the Oasis Gardens. In the water there are water lettuce plants and red mangroves. This vegetation is to ensure shade for the tilapia in the pond, create an ecosystem for the frogs, can be harvested for mulch and cleans the water.
Costs As the majority of materials for this project consisted of natural materials such rock, dirt, sand, straw, compost, ant litter, and biochar, the cost to construct the Oasis Gardens was minimal. In actuality, the monetary cost of constructing the Chinampa plot was about $24.00, which consisted entirely of the poly sandbags that were used to form the structure of the bed walls. As the rubber air mattresses and shade cloth that were used as liners no longer held air or functioned as originally intended, by using them in the chinampa, we are able to keep them from being discarded in a landfill and are repurposing them for a more meaningful and beneficial purpose. In regards to environmental costs, if the manufacturing of synthetic rubber materials emits 1,780 tons of Carbon Dioxide (CO2) per $1 million spent, and 1 mattress costs $20, then the manufacturing of 1 synthetic rubber air mattress emits about .0356 tons of CO2 equivalent. With 17 air mattresses used in the construction of the chinampas plot, that means the estimated emissions resulting from synthetic rubber manufacturing is .6052 tons of CO2 equivalent. For poly sandbags, if 736 tons of CO2 equivalent are emitted per $1 million spent, and one sandbag costs about $0.30, the emissions of one bag is estimated to be around .0002214 tons of CO2 equivalent, which when calculated by the 80 bags used, comes out to be around .017712 tons of CO2 equivalent. *Estimates include emissions of Carbon (CO2), Methane (CH4), Nitrous Oxide (NO2), and Hydrofloric Carbons (HFC).
Key Findings
If there was anything of significance learned from this process, it would be to plan for resiliency, think creatively, and be perseverant. When building a structure in a wetland area, all factors had to be considered. How much will the water level vary? What materials do we have to work with? How well will the water drain? How stable can we make the walls? How can we ensure water flow? How can we minimize anaerobic bacterial growth? This was certainly not all discussed prior to beginning the design and construction process, but by getting in the water (literally), and getting a close-up look at the problem and understanding it, it was possible to iterate and problem solve for each situation as they arose. Sometimes ideas worked well the first try, other times, it took a couple of attempts. In the end, a system was built with as much resiliency as could be anticipated and incorporated. Another useful finding is that Tilapia are great for cleaning a pond system. After finishing the chinampa plot, bacterial ridden water began wicking through the side of the wall, creating an oil-like stream across the surface of the pond. With the addition of the large amount of mosquito larvae, concerns began to grow about the viability of this project. However, within 24 hours after adding 15 small Tilapia to the OG pond, the water was completely clear, not even murky from the clay, and the mosquito larvae were gone.
Next Steps The immediate next steps will be to see how well the plants grow. However, assuming they do grow well, there is an opportunity for an additional Chinampa plot in the OG pond, but as previously mentioned, there is also the opportunity for continuing the expansion of the irrigation system behind the Oasis Gardens. Once the system is expanded, the model of this chinampa inspired system could be applied in a significantly larger scale and even leading to the full production of all food consumed at Kalu Yala on the Kalu Yala Farm. Another opportunity for the future of this project would be to conduct a full cost-benefit analysis, in both monetary and environmental terms. In monetary terms, once the value of a single harvest can be estimated, we can easily compare this against the costs and determine the net savings. In environmental terms, if we can estimate the carbon sequestered along with all activity performed within the garden bed itself and compare this against the environmental costs of manufacturing used materials and the carbon released from disturbing the dirt, the net environmental impact can also be added to the cost-benefit analysis.
Resources Since the Spanish conquered the Aztecs, Chinamaps went largely unused. Therefore, apart from what brief history exists, there does not appear to be much information on the
actual implementation and productivity of these agricultural techniques. While there have been some other organizations who have published their ideas for Chinampas, it seems to be mostly theory. That being said, it is fortunate that the director of the Agriculture Program, Jon Trimarco, had previously experimented with a chinampa inspired system on his own and had some key insights into how to best design the system. In addition, environmental costs for manufactured components were estimated using data collected by Clare Bassi, Sustainability Coordinator, in conjunction with data available online with EIOLCA.net.
Exhibit
References
http://www.specialtyproduce.com/produce/Red_Zebra_Tomatoes_10860.ph p http://www.specialtyproduce.com/produce/Beefsteak_Tomatoes_6926.php http://www.ancient-origins.net/ancient-places-americas/chinampas-floatinggardens-mexico-001537
Plant List Red Zebra Tomato
Description: These tomatoes are very flavorful and used for fresh eating, roasting, or used to create sauces. Red tomatoes have a high antioxidant content and lycopene concentration. The lycopene concentration accounts for the red color and has been found in studies to prevent certain types of cancer. They are rich in vitamin C as well as offering a good amount of vitamins A and B, also a good source of calcium and iron.
Beefsteak Tomatoes
Description:
These tomatoes are named for their size as well as meaty texture. They are rich in vitamins A and C with high amounts of fiber. Just like all tomatoes these are too found to help prevent types of cancers.
Red Mangroves
Description: Broad leaved trees that have aboveground prop roots that help to transport air to the roots underground which are waterlogged.
Beets
Swiss Chard
Bib Lettuce
Sunflower
Thai Basil
Oregano
Bush Beans
Malibar Spinach
Watercress
Eggplant