Sunday, October 3, 2010

Projects on the rooftop

This past month has been my first full month of managing my own area here on the farm. Most of ECHO's 10 interns oversee a section of the "global farm," an intensively managed 5-acre sector of the farm used for training, demonstration and experimentation. This global farm is divided into 6 "climatic zones," each with a unique set of constraints and challenges, and each demonstrating techniques that can be employed to meet those challenges. The monsoon, tropical lowlands, semi-arid, tropical rain forest, and mountain gardens are differentiated primarily by water availability (here approximated through irrigation schedules) and topography. While none of these model gardens replicate the exact challenges found in their real-life counterparts, they suffice as environments to demonstrate appropriate cropping systems and for some rough experimentation.

Brandon, growing corn on the side of his mountain.  Which is actually a sand dune!  Photo (c) Brandon Lingbeek.

The sixth section of the global farm, and the one put under my charge, demonstrates urban gardens.   Nearly 50% of the world's population now lives in cities.  The migration to urban centers is far from over, especially in developing countries where cities offer a false promise of prosperity.  Many of Africa's large cities contain sprawling slums built by former agrarians who were unable to secure the easy life they had hoped for in the city.  Nearly 1 billion people are now thought to live in slums[1], and with little infrastructure and even less money, access to fresh vegetables, herbs or flowers is often severely limited in these populations.  Growing food in such crowded conditions is possible, but offers some significant challenges, the foremost of which is severe space constrictions. Part of my job at Echo is to maintain and develop this demonstration area, seeking ways to overcome these challenges using materials that are commonly available, even to the urban poor.

Here are a few examples of recent projects:

Rebuilding a wading pool garden

Most of what I work with on the "rooftop" portion of the urban garden is basically glorified container gardening.  The containers are all recycled from other uses (cement mixing trays, tires, etc) and other external inputs are somewhat limited.  In this case, I had an old child's wading pool that needed to be rebuilt.[2]

I recently purged hot pepper plants from this bed that were suffering not only from old age (they were into their 3rd year of production) but from a bad case of parasitic nematodes.  As a result, I decided to try to rid this bed of nematodes before planting and rebuild it from scratch.[3]  I emptied and washed the wading pool and its non-soil contents, spread the soil out on a tarp, and let everything lay around in the sun for a few days to solarize[4].

I then added, in order, old aluminum cans[5] and plastic grids[6], weeds, chicken manure[7], hay, solarized soil[8], and more hay mulch:

The aluminum cans act to provide a water reservoir without saturating the soil.   The weeds, chicken manure, and hay will hopefully decompose slowly over the coming year, acting as a slow-release fertilizer of sorts.  The actual soil layer is thin, no more than a few inches thick.

This bed was intended for Malabar spinach (Basella rubra), a vining edible green that requires a trellis.  I wanted a round trellis with a large accessible surface area that required only one pole, since long poles are not always in ready supply.    Here's the result:

The Malabar spinach are transplanted and growing - I'll try to post an update picture later in the year.

Replanting a carpet garden

Many visitors ask if we do any hydroponics, having heard of the many benefits these systems offer[9].  However, most hydroponics systems are complex, requiring many plastic parts and expensive water testing equipment, and are therefore far out of the reach of the average poor urban dweller.  Then again, hydroponics does offer to reduce the need for soil, which can be difficult to acquire in paved cityscapes.  Moreover, feedback from ECHO's network members has indicated that city residents are often concerned about the weight of soil on top of their roofs.  So while hydroponics systems are unfeasible, we've developed several soil-less systems that are decidedly more crude, but still effective.

These 2 m.+ Lagos spinach were grown without soil!

A carpet garden uses a carpet (or other wicking mat or fabric) to deliver water and liquid nutrients to the plant's roots.  The water is supplied by an inverted bucket.  A small hole in the bucket's lid allows water to seep into the carpet throughout the day.  Evaporation is reduced using a mulch (in this case we're using corn cobs, aluminum cans, and pine cones to cover the carpet, but virtually any solid material can be a mulch).

Corn cobs - or virtually any other inert substance - can serve as a mulch

The plants are rooted directly into the carpet

Previously, this bed contained yellow eggplants, habanero peppers and Lagos spinach (Celosia argentea var. argentea), a west African green leafy vegetable.  Of these, the Lagos spinach flourished most, providing lots of vegetative growth, attracting a myriad of pollinators and producing copious seeds for the seedbank.  If anyone wants any seed, send me a SASE.[10]

I tore out these plants to make room for a fall crop of lima beans (Phaseolus lunatus 'Hopi Red')[11].  My first attempt, a direct seeding of soaked beans, failed miserably as the germinating beans were eaten by tiny yellow snails.  I'm now trying again, this time using transplants.

Lima beans in the greenhouse, ready for transplant!

Hanging gardens

Where horizontal space is limited, vertical space is often not.  If you have a sunny wall or overhang, a hanging garden can allow you to intercept underutilized sunlight and turn it into food or flowers!  One Saturday morning I decided to try to make one, so of course I headed to the nearest rubbish bin to look for supplies.

The first trash receptacle yielded two empty fertilizer bags; some rusty landscape stakes and a piece of rope soon followed. As this is a first attempt, I opted to plant cherry tomatoes, since they're known to respond well to hanging containers.  I filled the bags, secured the tops with landscape stakes, and hung them up with the rope.  I then punched four holes in each bag and gently maneuvered a bare-rooted tomato seedling into each.

My next challenge was watering them.  One of the advantages of this design is that evaporation is virtually eliminated - most of my water loss will be through transpiration from the plant's leaves.  However, this also means that the system must be hydrated by an IV line.  I ended up settling on a gravity-fed siphon system from a gallon-sized milk jug placed above the hanging bags.  I used drip irrigation tubing, but any kind of small-diameter tubing should work.  To water, I merely suck on the drip tubing to start the flow, then insert it into a hole in the sack.

Apologies for the length of this post... I'm trying to move toward shorter posts with better regularity, but this is obviously a step in the wrong direction.  If you're still reading this... well thanks. I'll stop now.


[1] According to this 2007 UN-Habitat report.
[2] "Rebuilt" because soil is a living system that doesn't usually thrive in containers.  Mixing in organic matter occasionally feeds the soil, improves its structure, and gives you a chance to combat diseases that are normally regulated by soil life.
[3] While gardening in containers restricts the amount of soil and soil life you have providing water and nutrients, buffering against fluctuations in pH and regulating disease organisms, it does give you slightly more control over your variables.  If I had the choice, I would choose the ecosystem services of a healthy natural system over the increased control of an artificial one, but I'll take what I can get. :)
[4] The sun can be a sterilizing agent in at least three ways: 1) Through heat released by absorption, 2) UV destruction on life in surface material, and 3) through dessication.  In this case, while the wading pool is probably near-sterile, I have no idea how well I sterilized my soil.  Since some nematodes can undergo cryptobiosis, I doubt simple dessication was sufficient to wipe them out.  Likewise, my soil was probably not spread out thinly enough for UV sterilization to have been complete, and I didn't have enough clear plastic to cover the soil and achieve the high temperatures necessary for heat sterilization.  But the method is simple and worth trying.  We'll see how it goes.
[5] Aluminum cans would rarely be a trash item in the developing world, considering the income-generation of their superior recycling systems.  But they are trash here, so that's what I used.
[6] I think the plastic grids originated  as the bottoms of plant trays.  Any kind of water-permeable material that supports soil would work here.
[7] From chickens raised on my rooftop.  More about nutrient cycling in a later post.
[8] The downside of sterilizing soil is that it also wipes out the beneficial soil life, without which soil becomes a dead system with no future, also known as dirt.  I added a few handfuls of healthy compost to this soil to try to reintroduce life.
[9] These being, primarily, the ability to divorce production from the climate, weather, soil, and other independent environmental factors.   Hydroponics cashes in a relationship with a vibrant soil life system for the control offered by a fully artificial system.  Why anyone would want to choose power over life is beyond me, even if it means boosting "production".
[10] SASE = Self-addressed stamped envelope.  My address is 17391 Durrance rd., North Fort Myers, FL, 33917.  While supplies last.  They won't run out.
[11] Everything at ECHO seems to be some sort of experiment, and this is certainly no exception.  I have no idea whether the nitrogen-fixing bacteria necessary for root nodulation are already present in the wet carpet, or whether they'll even survive and form symbiosis if I inoculate it with them.  I guess we'll find out!


  1. fascinating! what a great post! you really get to use your inventive mind. :-)

  2. Im interested in seeing the hyperboloidal trellis and hanging tomato bag planter with more growth on them. clever ideas, both. you write well. If martin ever wants to update his famous rooftop tech note, you should pen it.