Valldaura forest is a post-agriculture, post-industrial landscape which is now returning to native forestry. Cistercian monks turned the Valldaura (valley of the laurels) area of Colserolla national park into agricultural land in the 19th century, the evidence of which still remains in the terraced beds we will grow produce on as part of our Ecological Interactions program.
Some of the biggest global challenges we face today revolve around food production and how we manage agricultural land to feed a growing population whilst causing less damage to the environment, maintaining biodiversity and restoring soil health all against the backdrop of climate change – of which agriculture is a primary cause of as well as hugely threatened by.
From degradation of top-soil, biodiversity loss and agricultural practices driving climate change, our relationship with our food systems is one of the biggest challenges we face as a society and is a vital dimension to consider when developing sustainable and livable biocities. The practice we are learning on the Ecological Interactions programme at Valldaura integrates the principles of organic agriculture which overlaps with several other key agriculture practices including; permaculture, regenerative agriculture, agroecology, agroforestry and restorative agriculture. Through these methods, our syllabus educates on the changing paradigm of agriculture from:
Our journey into stewardship of the Valldaura gardens started with learning a key principle of restorative organic agriculture – the process of restoring the soil’s capacity to heal itself. Growing organic produce is as much about cultivating soil health as it is growing plants and with the constraint of not using any chemical fertilisers, pesticides, fungicides or herbicides our first task was to prepare growing beds as part of a Nitrogen cycle crop rotation system.
Nitrogen, along with phosphorus and potassium, is an essential nutrient for healthy, productive plant growth (as well as water, sunlight, temperature and oxygen/CO2) but is depleted over time as plants metabolize it in the growth of plant cells and tissues. In synthetically fertilised crops, this nitrogen content is often added artificially from fossil-fuel based sources, the production of which is a direct and significant driver of climate change. In sustainable agriculture, nitrogen can be added into the soil organically using a crop rotation system where crops with different nitrogen needs are grown in the same field in sequential seasons.
Nitrogen-cycle crop rotation
Nitrogen cycle crop rotation involves a seasonal rotation of 5 key crops types, classified by differing levels of nitrogen needed to grow into healthy plants. Legumes, such as fava beans and peas, ‘fix’ nitrogen into the soil through the symbiotic relationship they have with bacteria at their roots.
Rhizobia bacteria convert atmospheric nitrogen into nitrates in nodules at legume roots
These bacteria, named rhizobia, form nodules at the plant root which convert atmospheric nitrogen into ammonia that is converted into plant-usable nitrogen compounds such as ammonia and nitrate. In exchange for this nitrogen, the plant provides carbohydrates to the bacteria. Our crop rotation method utilises this relationship by planting legumes into the first and last groups in our 5-part rotation – the first as ‘green manure’ where the resulting grown plants (and their nitrogen) are chopped and turned back into the soil, followed by plant types which demand sequentially less nitrogen in their growth; brassicasaea, roots, leafy and finally legumes which are grown to harvest as produce. In doing so, nitrogen is added to the soil before the most demanding plants start to deplete it in their growth, before you reach the end of the cycle and reintroduce legumes to begin the cycle again.
An aerial photo of the Valldaura garden beds mid-way through preparation for the nitrogen cycle rotation.
The story of our Autumn/Winter rotation
The work on the garden started at he beginning of October, 2023. The conditions found were dry soil covered by weeds. Because of that, the first task was weeding by hand or a tool to remove all plants by its root. After that, a hoe was used to break the soil to make it more loose, so it allows more moisture and oxygen in, whilst allowing plant roots to grow. However, it can not go too deep and causes too much disturbance, otherwise it will destroy the soil microbiology by tearing fungi networks and removing plant roots which maintain the soil health.
In order to bring more nutrients to the soil in an organic way, the next step consisted of carrying manure and mixing it to the ground. Each bed received around 3 wheelbarrow loads of manure. The last stage of preparing the soil was to cover it with straw, which has several purposes, such as: to retain moisture in the soil to reduce evaporation; to break down and add nutrients to the soil; to prevent frost heaving in winter and to prevent weeds from growing. In sequence, the beds were watered for a few minutes, making sure it reached the soil under the straw.
First day of work at the garden, that was covered by weeds
When all the beds were ready, we started planting some seedlings according to the nitrogen-cycle crop rotation. In our distribution, beds 06 to 10 were destined to leafs, so the 6th got celery, for example. At that moment, the pipes were positioned on top, but over the next weeks they were placed under the straw on top of the soil (and close to the plants).
Weedling work done using a hoe; Beds covered with manure and also with straw; Prepped beds with manure & mulch.
When all the beds were ready, we started planting some seedlings according to the nitrogen-cycle crop rotation. In our distribution, beds 06 to 10 were destined to leafs, so the 6th got celery, for example. At that moment, the pipes were positioned on top, but over the next weeks they were placed under the straw on top of the soil (and close to the plants).
Seedlings of celery planted in the bed R1.06
After a bed received its seedlings, we drew a plan of them on a piece of paper along with the name of the plant and when it was planted. Later on, they were placed side by side on a wall from the Agrilab, so we could have an overview of all the beds of the garden. We also organised the beds digitally, using a shared Google Spreadsheets to gather bed information. Each bed has its code, a space to represent a plan of the seedlings, one board to write about “issues” and another to point out some observations. The main table has all the data about what was planted: the name of the plant, planting distance, quantity, the date it was planted, the expected harvested day and the harvested weight.
Example of our analog and digital coding system for bed planting
The seedlings that were planted are as follows:
- Brassicaceae (beds 01 to 05): Maravilla Lettuce, Kohlrabi Cabbage, Curly Lettuce, Broccoli, Cabbage, Romanesca, Kale
- Leafy (beds 06 to 10): Celery, Spinach, Lettuce, Chard, Rainbow chard, Coriander, Rocket, Mustard, Swiss Chard
- Roots (beds 11 to 15): Orange Carrot, Turnip, Purple Carrot, Beetroot, Long Beetroot, Leeks and Onions
- Legumes (beds 16 to 20): Fennel
- Green manure (beds 21 to 29): Fava Beans, Radish, Edamame peas, Green peas, Garlic
- Calçots
Some months later, some seeds or seedlings did not thrive and many were attacked by the wild boars. We also planted some seedlings from our greenhouse in the beds, but they were also attacked. After almost three months, we have in our garden calçots, radish, garlic, mustard, celery, fennel, coriander and leeks, but none were still harvested.
The garden, unlike conventional work schedules, doesn’t have weekends or holidays. It demands our attention every day. To manage this & in order to have better communication regarding what is going on in the garden, we managed a “Garden” channel on Slack, so everyone could report any news, update about the activities and demands, and also link with “Notion” and the tasks that were uploaded there.
“Notion” is a versatile tool that can be adapted for various purposes, from personal note-taking to collaborative project management. In our case, it was used to manage and link all of our content at one place. In that case, from the home page it is possible to access the “to-do list”, a “done and observations” list, a link that takes to the spreadsheet from Google Drive, a shopping list, a page to write some questions to take to our garden classes, a page about our compost bin (how it works, how to do the maintenance etc), a greenhouse wiki (information and tips about our greenhouse), experiments, and Plant ID.
Compost
Another important element of an organic garden is Compost. Composting involves the decomposition of organic waste materials from Valldaura such as kitchen waste, straw, weeds and Topinambur clippings into a nutrient-rich natural fertiliser that provides plants with essential nutrients, improves soil structure, and promotes healthy root growth.
We rapidly designed & built a compost bin at the garden, optimising the process of adding turning and monitoring the ~10kg of organic matter we added to the compost daily. Reaching temperatures of up to 45° our compost bin was very active. Presence of an ash-like substance points to mycelium life, which, along with bacteria, help to break down complex organic compounds into simpler forms that can be used by other microorganisms. We learnt about the complex and dynamic microbiology of compost and how to control bacterial and fungal digestion of organic matter.
In general, over the last 3 months, the MAEBB team have:
- Prepared & planted 30 beds (upper level)
- Prepared 32 beds for Spring/Summer rotation on the lower level
- Worked in the garden approximately 800 people hours (4 groups of 5 people working 1 hr/ week for 10 weeks) + (25 students x 3 hours each Monday taught lesson)
This illustrates how labour intensive organic farming can be – from managing daily tasks to responding to issues like boar attacks, irrigation leaks, water shortages and weather disturbances. Our single biggest disturbance came from Wild Boar, which would halt our progress on an almost daily basis. The Boar is the largest wild mammal in Collserola, and their population has grown dramatically in recent years. Despite many preventative measures; installing fences, the presence of a guard dog, making loud noises, the boar entered our gardens repeatedly, turning over beds and eating seedlings. Given the immature stage of our garden, these visits caused enough damage to effectively halter our progress as new seedlings did not have the chance to mature.
Despite the significant impact of the Boars on our production, some lessons have been learnt which we look to use in our Spring/Summer rotation. Boars avoided contact with certain crops; Raddish, Calcots, Garlic, Mustard leaves and Celery. Could these crops be used as companion plants to protect others?
To counter the impact of seedling attacks, we initiated the practice of transplanting seedlings germinated in our greenhouse.
The Solar Greenhouse
Exterior view of the greenhouse
The growing capacity at Valldaura Labs was increased with the introduction of the Solar Greenhouse project, built by students on the 2021/22 cycle of the programme. The Solar Greenhouse – a prototype of an urban greenhouse which uses LED grow lights and hydroponic water systems – provides optimized conditions to germinate seeds for our main beds, as well as space to experiment with growing conditions by carefully monitoring the levels of light, nutrients and temperature.
The first weeks of our term involved familiarising our team with the systems in the greenhouse – used to automatically water and provide nutrients to plants. Modifications were also made to increase the temperature of the structure in the colder winter months – in a process of constantly learning and improving the structures at Valldaura.
Germinating seeds requires a careful balance of several conditions, critically the presence of water and warmth to begin the process of germination. The Solar Greenhouse provides the perfect conditions for this and in the spirit of learning by doing, we set about experimenting with a variety of seeds, growing mediums, germination temperatures and nutrient levels in our automated water system.
Exploring the effect of different substrates during the germination phase and investigating how heat and the addition of a coconut fiber layer under the sawdust growing medium impact plant maturation
Germination process from prepping beds, selecting seeds, planting, monitoring, transplanting into larger containers, transplanting into open beds or upper greenhouse beds and harvesting micro-greens
An important part of our relationship with the Valldaura garden is data-collection. A digital seeding log has been a useful tool to retain information and effectively understand and manage the conditions in the greenhouse. From this log, we can trace transplanted produce back to its seedling stage to understand what impact the grow conditions have through the plant’s life
The following list details the variety of seeds successfully germinated in the Solar Greenhouse this term;
Fava beans, Edamame beans, Radish, Basil, Spinach, padron peppers, cayenne peppers, montserrat & muchamel tomato, cebolja morada, gem lettuce, chard, ticket, chives and black beans.
The first few months in the greenhouse has given us a solid foundation to germinate seeds ready for the Spring/Summer rotation and to provide produce for the Macquina Climatica exhibition occurring in Spring as part of our collaborative design studio project.
Plant Taxonomy and biology workshops
To gain a deeper understanding of the plants we will be growing in our gardens, we learnt about plant biology, genetic reproduction and taxonomy. We explored how plants reproduce (sexually, or asexually) and were taught the structures which contain genetic information (chromosones) which can vary in number across different species of plant. Haploids (1 set of chromosomes) diploid (2 sets) triploids (3 sets) and so on. We summarised this data into botanic classification drawings which contain our knowledge of plant biology, uses, growing seasons, companion species and more.
Soil health, microbiology and threats from intensive agriculture
As mentioned earlier, restorative agriculture is as much about restoring soil health as it is growing produce. Soil health is crucial for food productivity and other important ecological factors including providing habitats, capturing carbon and helping to mitigate damage from water.
Soil should be thought of as more than simply dirt – instead it is a complex mixture vegetative matter, eroded rock and minerals, decaying plants and animals, air, water and a hugely complex interconnected web of microorganisms including bacteria, fungi, algae, protozoa and nematodes. This complex ecosystem supports an estimated more than half of Earth’s species 1 and is crucial in maintaining soil health, fertility and productivity.
This soil ecosystem can be understood in trophic levels which captures how energy is transferred between species in an ecosystem. In a soil food web, these levels flow from producers (plants), which use the sun’s energy to produce organic matter in a process called photosynthesis, to the second trophic level consisting of consumers such as bacteria and fungi through 3rd, 4th and 5th trophic levels of varying higher-level predators.
Soils can be classified by their texture or composition – varying percentages of clay, sand or silt of which influences the soil’s ability to retain water and nutrients and to support different types of plant species. Simplified flow diagrams are helpful in understanding soil texture and help to gain a more intuitive connection to our land.
Soils can be further characterised by their horizons, or the varying layers of depth that have different physical, chemical and biological characteristics. From the uppermost organic (O) horizon, we work down through A, B C horizons before arriving at bedrock (R ) composed of solid rock.
Horizon C, or the topsoil, is the layer which is important for plant growth and nutrient cycling – hosting most of the biological activity and which is being lost through soil erosion on unprecedented levels. According to a report by the Food and Agriculture Organization (FAO), 33% of the Earth’s soils are already degraded and over 90% could become degraded by 2050 5. Part of what sustainable agriculture teaches is to retain and replenish the health of soils through organic methods, which recover soil health and resilience by supporting the complex web of microorganisms which keeps the soil from eroding.
Onto the Spring/Summer rotation
The Autumn and Winter rotation of our garden has not yielded the produce we expected when setting out on our journey with the land here at Valldaura labs. To have so little to show for our efforts in making our beds productive is disappointing but a very pressing lesson in the challenges that face organic producers all over the world.
Growing produce in a way that doesn’t damage our local ecosystem is a difficult task, where threats from disease, drought and especially in our case; pests in the form of wild boar, become constant barriers to produce abundance. Our garden is one tiny part of a much bigger ecosystem, and learning ways to fit into that without making the same mistakes as some of our post-industrial societies have done in pursuit of food abundance is a rewarding and necessary challenge.
That being said, the lessons learnt along the way, both in the scientific composition of an organic garden as well as the organisation and regular labour involved in maintaining one are vital to understand the challenges facing cities in moving towards food self-sufficiency. Most importantly, we have developed a mindset of iterative and responsive design in response to the ever-changing variables of a natural environment. Learning to observe and understand what our land needs gives us a solid foundation to build on for the Spring Summer rotation, with a renewed determination to beat the boars!
References
- World Soil Day: Why is healthy soil so important? (2023, December 5). BBC Newsround. ↩︎
- Benefits of a healthy soil food web. (n.d.). ↩︎
- Babür, E., & Dindaroğlu, T. (2020). Seasonal changes of soil organic carbon and microbial biomass carbon in different forest ecosystems. In IntechOpen eBooks. https://doi.org/10.5772/intechopen.90656 ↩︎
- Soil Texture Map. (n.d.). ↩︎
- Key messages | Global Symposium on Soil Erosion | Food and Agriculture Organization of the United Nations (fao.org) ↩︎
