Companion Planting in the Tropics – Vertical Stacking

Sweet potato and katuk (sweet leaf/sayur manis)

We have been playing around with companion planting at Project Canossian. Actually it’s more of stacking plants on top of one another rather than just adjacent. Lots of failures with some successes. It is something we have been experimenting with since our days at Project Green Valley. There are many good reasons why you would want to companion plant by vertical stacking:

  • Better use of sunshine: Here in Singapore 1 degree north of the equator, the sun is overhead throughout the year. As Bill Mollison says, a resource that isn’t properly utilized can become a pollution. Sunshine is photosynthesized by leaves and is turned into a yield (for us or other living things). However, when this strong sunshine falls on the soil many things happen. Soil water evaporates, soil organisms (e.g. earthworms) die from the heat, ambient temperature increases due to radiation. A single layer planting of small vegetables or herbs does not use the sunshine efficiently. Lets talk about planting lettuce as an example: for most of the growing duration, most of the sunshine will fall between the tiny seedlings onto the soil. Even when the lettuces are fully grown and touching one another, the leaves are not able to utilize all that good sunshine. One layer of leaf can only photosynthesize so much sunlight, after which the remaining passes through the leaf. Which is why the best use of sunshine here in our climate is still a forest. Almost all of the solar energy would be extracted as the sunshine passes through the many layers. Nothing much is left by the time it reaches the forest floor.
  • Better use of rainfall: Likewise, we are blessed (or, to poly-tunnel farmers, cursed) with heavy rains throughout the year. The kinetic energy of falling raindrops causes soil compaction and sheet erosion when not absorbed by foliage or mulch. Having more leaves to intercept and direct the water flow down the stems allows the soil to drink more gently. If there are not enough roots in the soil to absorb the rain it flows away, causing leaching of nutrients.
  • Shading out weeds: Nature doesn’t waste. Solar energy that falls on soil will be taken up by weeds. Mulching helps but we have seen weeds here that can penetrate mulch (cardboard or leaves) just to reach for sunlight.

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Project Lombong – Ten acres of bare soil…

We are starting on a 10-acre piece of land in Johor, Malaysia. It is situated close to Kota Tinggi, a place north-east of Singapore known for fireflies and waterfalls. Kevin approached us recently about this land owned by his family. He wants to do organic farming on it and provide good livelihoods to people working there. The majority of the area will be a mixed fruit orchard but there will be aquaculture and vegetables too. He does not have any farming experience, but we felt that he has good intentions and is someone we can work with.

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View from the highest point

The land was previously a 3 year old rubber monoculture plantation. When we met him, the land had already been cleared of vegetation by a tractor. He said that the contractor was going to dig up all the tree roots and dispose of them. We recommended against that for many reasons:

  • The roots, despite being dead, still holds the soil together against erosion on his sloping land. Over time, they will rot and act as a slow-release fertilizer.
  • Digging mixes up the naturally-formed soil horizons and disrupts all the organisms in the soil.
  • Aerating soil in this manner introduces a rush of oxygen into the soil. That’s a short-term benefit with long-term losses. With the high temperature and moisture here, this means that organic matter and humus decompose rapidly and become lost as carbon dioxide to the atmosphere.
  • Without any big trees or plants to absorb the suddenly available nutrients, they will be lost to the atmosphere (oxidized) or washed away by the rain (leached).

After the first meeting, we scheduled a date to visit the land. Continue reading

Project Canossian – Chop-and-Drop (Part 2)

Sounding as bad-ass and violent as natural farming (not industrial farming) can ever get, chop-and-drop is actually a really effective gardening technique. Simply put, one chops the existing plant down and drops them right away on the spot where the next plant is to grow. Combined with green manuring, it is an excellent way to kickstart your garden

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Green manure growing out of the beds

Our previous post on Project Canossian ended with a round of green manure. Over the next month or two, the green manure helped to:

  • Fix nitrogen: roots of legumes (beans and peas) act symbiotically with certain fungi to convert nitrogen in the air to the soil for plants to absorb
  • Create biomass: the vigorous growth means that you get a mass of organic matter for mulching when you chop-and-drop
  • Settle the soil: gives time for the newly poured soil and compost to stabilize

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Project Canossian – Building A Garden With Waste (Part 1)

A few months back, we built a food garden for the Canossian School in Singapore. They work with kids with hearing impairment and the school principal Terry wanted a sensory garden for the kids to develop all their senses. She lamented a few times about how children nowadays do not get to pull things out of the soil.

Canossian School is very fortunate because they actually have unused space for a garden. We have spoken to many schools that want a food garden but do not have any space left. We would walk the school grounds to find that everywhere has been concreted or planted with trees. Canossian School has a sizeable and flat grass patch and we were allocated about 35m x 11m for the garden.

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The possibilities are endless, like a blank canvas.

Analyzing the Site

Before even thinking about garden design, we needed to understand the site. From a distance, we noticed many bare patches that grass did not grow on. That’s not a good sign. The type of vegetation growing on it was odd as well. Walking the ground, we immediately noticed that the soil was soft. It was not the spongy softness of a soil with good structure and many pores. It was a muddy kind of softness like wet pottery clay. As expected, there had been major soil works about a year ago. We learned that there is construction waste like concrete rubble beneath the soil. There is no top soil but just a layer of yellow clay. It’s not a great start but we are used to all these in urban environments. Continue reading

Made in Singapore – The Story of Three Veggies

Over the weekend, I gave a talk at a conference in downtown Singapore. The conference is called FutureME and showcases emerging ideas, innovation and trends shaping our future. There were a few speakers addressing urban farming and local food. I guess that people in Singapore are becoming more concerned about food issues.

My talk was probably the shortest. It is a story of three locally grown vegetables. It is a response to the many high-tech growing systems that I am starting to see more of only recently. Hydroponics, aeroponics, aquaponics, indoor growing, soil-less growing, etc. Continue reading

Creating Terra Preta and Using Urine to Fertilize

We have been farming at Project Spectra for close to a year. The rooftop conditions are especially challenging with the heat and wind. Only certain plants that can adapt to these conditions do better at our garden, like beans and legumes.

2015-09-08 13.46.26 During the school holidays, we decided to do some soil amendment by adding biochar. Terra preta is man-made soil created by an ancient farming method in the Amazon Basin between 450 BC to AD 950. It literally means “black earth” because of the high charcoal and humus content in the soil. The ancient farmers have digging charcoal into the soil sometimes up to a depth of 2 meters. There are a few reasons for doing so:

  1. Biochar reduces nutrient leaching which is a major problem in places with very high rainfall, like the Amazon Rainforest and Singapore. Much of the plant nutrients are water-soluble and they get washed away during a heavy rain into the rivers (or in the case of SIngapore, the drains). Charcoal is extremely porous so they have a very high surface area to volume ratio and these pores hold on to the nutrients.
  2. The high porosity characteristic of charcoal also encourages microbial activities in the soil. They provide spaces for bacterial and fungi that help with the ecosystem of the soil.
  3. Biochar is slightly alkaline and helps to balance the pH of tropical soil, which is typically acidic.
  4. Biochar helps to moderate the wet and dry cycles in the soil. The numerous pores absorb moisture when the soil is wet and release them when the soil is dry. The roots of most plants enjoy a condition where it is moist enough but not too wet that they suffocate without air.
  5. Lastly, biochar will last a very long time in the soil. Unlike compost or ash, it doesn’t break down. This is why we still find Terra Preta in the Amazon after thousands of years. Talk about permanent agriculture!

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Project Spectra 3 – Building Biomass and Stablizing the Ecosystem

It has been over 3 months since we last updated about Project Spectra. Back then, we chopped and dropped the green manure to prepare for a round of planting. After leaving the green manure to break down in the soil for a week, we started planting works. Here is our progress so far.


While the garden today is very much different from what it was before, we are still dealing with many problems that come with starting a garden from scratch. There was zero life on this rooftop just a few months ago and you are creating a universe! The ecosystem is still unstable and the rooftop conditions are too hot and windy. We have started the process of restoring soil fertility through adding compost and green manure. However, there is still lots to be done by nature herself, and nature does not rush. Continue reading