Our objective is to make urban space more natural and have it produce food at the same time. We make green spaces more productive and natural. We acknowledge the urgency of becoming climate proof on every level: as a planet, as a city, as a neighbourhood and as a household. For this we need to learn how to grow food in the city and reconnect with nature. We teach and learn with the members of our community that want to be part of this new field of practice and knowledge. How to support what kind of ecosystems? Which biodiversity do we support? What kind of food production fits in these ecosystems?
Semi-raised Beds in Wheel shape
Our challenge in Riekerhaven was to transform a old football field with poor soil into a garden in several months. We decided to take the top layer of the soil of the paths (-10 cm) in between the beds, and put them on the beds, in order to double the future rooting zone. We made 21 beds of about two meter long and 1 meter wide. The sides of the beds we made of stone tiles (30cmx30cm), with 10cm of it sticking in the ground. The paths we filled up with carton to prevent weeds in the next months, and lots of wood chips. Each bed we covered with a few wheelbarrows of (oak)leaves and manure and plastic sheets with little aeration holes, so the old vegetation could start to decompose. In the late spring we removed the plastic and the left over organic matter, and the beds were entirely clean and warm for seeding! The next season hardly any grass came back. Only some innocent weeds. The idea is to grow some perennials in the beds, next to the annuals, like certain berries, who can profit of the growing fertility building up under the paths. Soon we will put back the leaves to protect the soil against drought and to further fertilize it. Our design mission for our “Wheel garden” was:
Maximum of self seeding and perennial plants
Easy to maintain and easy watering
Produce food that we can easily use in our daily life
High production per m2
All year round production
We choose for a wheel shape for easy reachability of all beds by walking from the kitchen, but also to make a circle for the sprinkler irrigation, and to have a clear layout for the crop rotation. This year we are mainly growing in these beds: Cabbage, Chard, Cauliflower, Spinach, Radish, Corn salad and Courgette. We decided to test out companion planting as a way to increase yield per m2. We try to mix in aliums as much as possible and also mix crops of different seasons (fe starting winter carrots during spring production of salads) Some wild plants that we allow to grow in the garden beds as "weed" and that we use and thus adds to our production: Chick weed, Rocket, Blind Nettle, Goosefoot, Clovers, Narrowleaf Plantain and Veronica.
Aquaponics is a revolutionary type of horticulture. Basically, it adds fish-breeding to hydroponics (aquaculture + hydroponics), inspired by traditional forms of agriculture such as the Sawas of Southeast Asia and the Chinampas of the Meso-Americas. It is a type of closed-loop food system. The fish excrements supply the fertility for plant growth, and the fish are fed with food scraps and insects grown in compost (soldier flies). If the fish are bred for consumption, it theoretically doubles the production of total food (calories) per m2 compared to the two growing systems operated apart. There are many types of aquaponics, such as floating raft production, or on a substrate with flood and drain irrigation. We choose for vertical gardening with buckets, in which the fish water runs through the pebbles in the buckets from the top downwards, and back into the fish basin. The solar pump works during the daytime for 15 minutes per hour, that is sufficient to keep the pebbles wet. Because the greenhouse is not systemically heated during winter, we chose for native, easy to keep fish (carp and roach). So, when plant production comes to a stand-still, the fish also go into "winter sleep" (hibernation).
10 liter Planters: recycled from shut-down marijuana plantations, left by the
Substrate: recycled rock-wool, expanded clay pebbles and lava rock (8-16 mm). Lava rock is cheaper than clay pebbles, but it can create basic water (high pH). We found that a 50/50% mix resulted in pH stable water.
Rack: untreated wooden beams, with 2 metal L's as top support for the planters
Pump: 200 Watt bilge pump
Tubes: 20 mm PE tubing, with holes and little reeds sticking out for each of the top row planters.
Aquarium and mix tank: Wooden boxes with pond liner
Maintenance The motivation to choose this system was not so much the fish production - we keep the quantity of fish to the minimum and don’t eat them - but rather an easy to maintain vertical garden. The system is fairly self regulating. If plant growth doesn’t seem right (slow growth, yellowing of leaves), some check-ups can be done regarding nutrient availability, for example with an EC meter. The EC meter measures conductivity of salts in the water and is thus a measure for salty nutrients. If the reading is lower than 1, there can be a problem, and a chemical analysis can be done to look at the levels of Potassium - which is one of the most important salts. Chemical test sets are quite cheap if not used regularly. pH is easy and cheap to measure with lakmoes/litmus papers. If the pH is higher than 7, the water is basic, and nutrients become less available for plants; therefore acidity needs to be added. One of our experiments in acidifying the water comes from our compost. We treat compost tea (drainage water from work compost, see next chapter) with EM1 (a mix of lacto-fermenting bacteria) and sugar beet juice. The compost tea with EM1 can be added in the mix tank, making the water more acidic because of the lactic-acid. In case the acidity needs to be raised, only some more sugar beet juice needs to be added to the water to activate the EM1 again. EM1 can be made DIY. The reason for this experiment is that it seems more natural than alternatives (just pouring some saltpeter acid in the mix tank). This also provides nutrition to the plants while keeping the fish population to a minimum, so you avoid not having enough fish-sourced "manure" for the plant production. Production We grow mainly kitchen herbs in this system, like Parsley, Basil, Celery and Mint. But Chard, Lettuce and Water Cress also grow very good.