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.

Building Biomass

As Bill Mollison said in the Permaculture Designers’ Manual, in the humid tropics 80-90% of fertility is in the biomass of plants. The heat and high rainfall would leach most mobile nutrients from soils. Therefore, the concept of storing nutrients in the soil would not work. Hoarding is a concept invented by humans; nature does not hoard. Hoarding might work with money and a bank (at least occasionally) but we are dealing with something alive here. It is the constant cycle of life and decay that will keep nutrients in the system.

The first round of building biomass was from the green manure legumes. They did an excellent job. We chopped them down and left all the biomass in the soil. Imagine the fertility leaching out of the system if we threw it away! The second round of planting was for a more permanent scape for the garden. I dedicated a substantial portion to edible perennials like fruit shrubs (bananas, passion fruit, papaya, lime, mulberry, etc), sweet potatoes, gingers, lemongrass, mint, purslane, rosemary, southern wood, and many more. Unlike annuals, the perennials will gain biomass and cycle nutrients and water.

2015-04-01 10.23.20I also planted a range of leguminous trees at different spots across the garden. While they all edible, the main objectives are for them to:

  1. Accumulate biomass for chop-and-drop (for mulching or composting),
  2. Create micro-climates, and
  3. Fix nitrogen into the soil.

They are pioneer plants and tend to survive better in hot, dry, and poor soils. The are good for interplanting between other crops as the foliage does not get too dense that they shade out the shorter plants beneath or around them.

The way that the concrete planters were designed is such that the pathways between them are very wide. While that creates ease of movement when the rooftop is full of students, it also means that a big portion of the sunlight hitting the rooftop will be wasted on concrete instead of being photosynthesized by plants.

2015-04-01 10.22.28

Glare from the concrete floor

A resource (sunlight) that is not properly used can create problems. Firstly, the solar radiation will heat up the rooftop and subsequently the entire building. Secondly, the sunlight reflected from the light coloured concrete floor will reflect onto other plants. Try standing on the rooftop at mid-day without squinting. Some of these plants are already struggling under 12 hours of direct overhead sun and any more is counter-productive.

For this, we built bamboo trellis over the concrete floor. With the trellis, the space above the pathways will double up as growing space. We have been harvesting lots of long beans. There are some cucurbits starting to climb on as well. The passion fruits are taking longer to climb because they already get sufficient sunlight and there is no motivation to waste energy climbing up. These climbing plants also help to provide shade for humans when we work in the garden.


Stabilizing the Ecosystem

2015-04-01 11.22.57

Spot me!

There was no ecosystem to start with when we first arrived. The rooftop was barren and there wasn’t a single plant, even grass. As with any immature ecosystem, there will be drastic movements as the system tries to stabilize itself. We have seen a round of aphid infestation, a round of millipede infestation, a round of caterpillar infestation, and more. What did we do? Nothing. Nature will sort out the infestation eventually. Many people think of the leaves that the caterpillars have eaten but they forget about how much manure these guys produce!

Surprisingly, the casualty rate was not too bad. For the established plants, they get eaten but they simply continue growing. They just have to grow faster than the caterpillars can eat them! We must have lost many seedlings but we merely continue sowing and some do grow up eventually. We also plant varieties like mustard and radish that somehow our caterpillars shun.

Here are some photos of the damage and also the biodiversity that arrived after our planting works.


The Harvest

For all the challenges we faced, we were lucky to be given a decent harvest. Our mulberry that got stripped bare in the photo above even grew back eventually to produce very sweet mulberries! Here are some photos of our harvest.


You can read all our posts about Project Spectra here. The school also has a Facebook page and there are many photos of the students planting and harvesting in the garden.

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