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!

Continue reading

Advertisements

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

Project Spectra 2 – Green Manure + Chop-and-Drop

Earlier, we posted about kickstarting the rooftop farm at Spectra Secondary School by growing green manure. You can read about that here. We are happy to report that the legumes have been growing very happily and rapidly. We have been intentionally lazy and have not watered or done anything. There is a time for us humans to work hard and there is also a time to sit back and watch nature do her magic. As expected, the monsoon rain really sped up the growth of our green manure.

Week 3

The legumes have sprouted and grown through the thin layer of mulch. You can literally see it growing by the day!


Continue reading

Project Spectra – Farming on a Rooftop

We were tasked to build a farm on the rooftop of Spectra Secondary School recently. It is a new secondary school in northern Singapore that focuses on vocational and practical skills so that students will be well-equipped to work upon graduation. The school’s philosophy behind this rooftop farm initiative is “No One Owes Us a Living – We Work Hard to Put Food on the Table”. As such, we will also be teaching the students how to farm organically. I have no doubt that it is out of this world for these city teenagers.

The barren rooftop when we first stepped onto it.

The barren rooftop when we first stepped onto it.

The good and also bad thing is that the infrastructure is already built. There are 11 big concrete planters filled with soil which means we can start growing soon. Unfortunately the soil has been left bare for a few months. In the tropics, this mistake was magnified by the baking sun and torrential rain. I learned from the school that the landscape contractor has scraped off the top layer of the soil because it was muddy. My guess is that the “mud” is actually the fertile top soil that got damaged by the elements. We are now left with the clay subsoil… Continue reading