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To Keith Addison

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Container Farming

Organic food production
in the slums of Mexico City

by Rodrigo A. Medellín Erdmann

By the middle of the 1990s, forty million Mexicans -- nearly half the total population -- fell below the poverty line. And of these at least 15 million live in extreme poverty -- above all in urban marginal areas like the slums of Mexico City. Some seven years ago ANADEGES, a group of some 20 autonomous NGOs, launched a project to help the people there to develop their own autonomous capacity to produce food organically in small backyards or patios, balconies, rooftops -- as a way to partially counteract the poverty being imposed upon them.

The technology had to address four constraints: little or no land, little or no investment in infrastructure, no purchase of chemical inputs, and be light weight for rooftop cultivation.

Three years were spent in a quasi-experimental stage. It is important to point out that these experiments were actually a trial and error process by an amateur with no agronomic training. An expert would have probably taken a much shorter time. On the other hand, an expert agronomist would probably not have dared to experiment with such lowly technology. During the last four years, the project has been introduced to several hundred families in six different slum areas of the city.

The starting point was a cultivation technology developed by Dr. Barbara Daniels in California, USA, in a nutshell: vegetables are grown in drainless containers ideally with 18 to 20 liters capacity -- stuffed with deciduous tree leaves or grass clippings up to 4/5ths of their capacity, topped by a three to five centimeter layer of good soil, where seeds are planted, or seedlings are transplanted. On the wall of the container, five to ten centimeters from the bottom, a hole is bored for drainage the container thus maintains a water reservoir at the bottom. Finally, a stick is inserted right down to the bottom, that is used to measure the containers' humidity as you would the oil in a car. A container thus prepared, weighs far less than one filled with regular soil.

The best organic fertilizer: urine

The key to this technology is fertilization. While chemical fertilizers can be used, Dr.Daniels suggests a much better alternative: an organic, domestically produced, high-power fertilizer. Regarding fertilizer, considering the expense of commercially prepared fertilizers, the amount needed for a full-size deck garden and the fact that many of them don't work well, I have found that urine is the best fertilizer for this system. The decaying leaf medium breaks it down almost instantly so that there is never any odor, and germ survival in material such as this has been shown to be practically nil. We call this liquid organic fertilizer (LOF).

The LOF, a key element in this technology, is abundant, with no cost, and easy to manufacture.

For several years the aim was to obtain empirical results in terms of low cost organic production of vegetables. During this time no thought was given to scientific experimentation. Consequently the results were gradually observed and understood in a merely empirical fashion, with little quantified data. We arrived at five main findings:

  1. Plants grew more rapidly, bigger and healthier than those grown with conventional agricultural techniques. Less water was needed.
  2. In the case of plants that produce edible leaves -- lettuce, spinach, Swiss chard, chives, parsley, quintoniles (Amaranthus hybridus), quelites (Chenoponium album), verdolagas (Portulaca oleracea) and all types of herbs -- the produce was outstanding. Leaves were big and bright dark green in color. Particularly remarkable was the nopal (Opuntia sp.), a cactus with big, green, prickly, pallet-like edible leaves, actually transformed stems, tender and fleshy (pencas in Spanish) very much appreciated in Mexico. It has excellent nutritious value: it has been called the Aztec beefsteak and serves as a natural medicine, for example, for diabetes.
  3. Some fruit-bearing plants, specially hot peppers essential in the Mexican diet, grew well and produced abundantly; but were not as hot as those conventionally grown.
  4. Other fruit-bearing plants did beautifully in their early stages, but rather poorly in terms of fruits. Such was the case of tomatoes, green tomatoes (Physalis pubescens), squash, beans, cauliflower, cucumber.
  5. Some experimentation was made with root plants, but not much, since the containers being used had a relatively small diameter, and could accommodate too few plants. There were good results with radishes. However, people would certainly be interested in onion and garlic. Carrots are usually so inexpensive in the market, it is not cost effective to cultivate them.

Other intriguing features: all plants did particularly well in their early stages; they proved remarkably resistant to insects, pests and diseases.

A warm bed for the plants

The next stage was to understand these first results, and to look for ways of improving them. In short:

LOF was an excellent source of nitrogen (N), readily absorbable by the plant. This was why the leaves did so well. In this technology there was a deficiency of phosphorus (P) and potassium (K); no idea about minor nutrients. The initial process inside the container was a very intensive anaerobic composting, which raises temperatures; this acted as a warm bed that helped plants in their early growing stages.

More puzzling was the resistance of plants to pests and diseases. In one instance, a set of tomato plants was growing near a tree heavily infested with the white fly. Many of these insects would fly around the plants ordinarily so prone to being attacked by them but not one landed on the leaves. They simply flew back to the tree. Eventually, an article in a German scientific journal gave us the clue. The composting process taking place inside the container produced substances that helped the plants become not only stronger, but also resistant to pests. An added bonus.

At the end of a year, the composted leaves had turned into a beautiful, rich soil. Each container produced enough soil to supply the top five centimeter layer in ten new containers, or for any other use.

If the technology was to be really useful to people, the missing elements had to be found. What was needed was a cheap, abundant, readily available, organic source of P and K, like we already had of N. Furthermore, these two major nutrients had to be immediately absorbable by plants, since their life cycle was so short: three or four months. It was not the case of some organic matter that could be mixed with soil to be decomposed over several months or years.

As is usually the case, the solution was found by chance, to a certain extent. For other reasons Anadeges began to experiment with worm raising, the type of red worms that process organic waste (Eisenia foetida). Eventually we realized their castings were exactly what we were looking for. They contain the P and K the plants need, readily absorbable, and can be produced abundantly and at no cost by the families themselves. Between LOF, worm castings and decaying leaves, plants also have enough minor nutrients. An additional environmental bonus: kitchen refuse could be recycled, instead of thrown into the garbage.

The aim of the project was to benefit families. Consequently, it was proposed to them once results were sufficiently satisfactory, without waiting for perfection. The lack of organic P and K was temporarily supplied with chemical fertilizers. It was important to check up on their acceptance, especially of LOF. In the last four years, the project was implemented among several hundred families in six slum areas of Mexico City.

For this stage, the project received partial financial support from GATE-ISAT in Germany and the St. Nikolaus Foundation in Sweden. A Mexican chain of supermarkets agreed to give the project all their used containers (we had to collect them and clean them), which was a great boost. We tried, but could not get any support from local Mexican government agencies at that time.

The project lessons

LOF was easily accepted, even though it was a conclusion reached through a quasi-maieutic dialogue: "We can make an agreement with mother earth, to give her what we no longer need, and ask her to provide us with what we need. What is it that we no longer need? etc"; along with a medical explanation confirming that urine is a clean and pure substance, and properly fermented is harmless.

To be constant in the care of a vegetable garden specially to overcome the difficulties in the early stages -- people need to have more than one of the following motivations, amongst others:

  • availability of food to improve nutrition
  • economic savings
  • a nice hobby for the whole family
  • healthier, fresher organic food
  • recuperation of agricultural skills -- most elders come from rural communities
  • closer contact with nature
  • increased political independence from government assistance
  • ecological concerns: recycling of garbage
  • container plants as house ornaments
  • relaxation from urban stress
  • friendship and meetings with other women raising plants.

People were willing to pay a price equivalent to costs for the implementing agency. In turn, during the first year families should harvest produce at least equivalent to the price they paid. This would eventually make the project self-financing.

It was mostly women that were interested in container vegetable gardening. And it is always a community activity. Besides food plants, women from slum areas began to request ornamental flowers and trees. We readily complied.

It is important to work in an organized context, so the implementing agency does not need to bear the burden of organizing people.

There should be relative tranquillity in the community, for people to dedicate enough time to their gardens. If there is political or other kind of unrest, people tend to be distracted and disregard their plants.


Further experimentation with the more complete fertilization system is necessary. In this context, soil pH is a variable that has to be better understood. We also plan more experimentation with wormfeed to include substances that could increase the percentage of P and K in the castings.

The project will expand to many more families and slum areas. At this stage some form of government support is likely, to open new areas, and to tackle other aspects of the project such as:

  • Utilization of discarded tires turned inside out, to be used as wide-mouth containers with greater capacity, excellent for root plants. This would also address a staggering ecological problem in a city like Mexico with literally mountains of used tires.
  • A shift from an artisan to an industrial production system with several production lines: plants, containers, worms, tires.
  • A drive to reach the financial break-even point, and achieve self-financing for the whole operation.
  • Start experimenting with backyard animals.

The project has been successful in perfecting a technology to cultivate vegetables in containers organically, with no industrial external inputs - by utilizing readily available, zero-cost waste matter and discarded containers. It is a sustainable urban agriculture system easy to expand, that can help people recover their autonomous capacity to reach a certain degree of self-sufficiency in food production. But much more needs to be done.


Barbara Daniels, Growing Plants in Containers: new guidelines for a deck garden. Multicopied. Fairfax, Ca., 1981. On several occasions the project tried to get in touch with Dr. Daniels, but could never locate her.

Tränkner, Andreas, Kompostextrakte kontra Schadenpilze, in Garten Organisch, 4/1990, pp. 13-15.

Rodrigo A. Medellín Erdmann is a sociologist who has been working with campesino and Indian communities and organizations in Mexico since 1974. He is a co-worker of ANADEGES -- "Autonomy, Decentralization and Self-management" -- created in 1982. One of the institutions of the group, Cedicar, manages the project described here.

ANADEGES -- Autonomía, Descentralismo y Gestión -- Socios Técnicos

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