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 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…

When we first stepped onto the rooftop, the white planters and concrete floor were so glaring that we could hardly open our eyes. The soil was very dry and hard. The funny thing is that it also floods after a heavy rain. Nothing was growing on it except a few small patches of grass. Apparently the landscape contractor has been painstakingly weeding the grass. Before we even started any planting, the first thing I told the school was to stop weeding. Leave the grass to grow! To understand why, read these posts.

On a hot day.

On a rainy day.

The school has been seeking advice from many sources including conventional farmers, ornamental landscapers, and government authorities. The advice has been very varied. Some proposed to dig up and throw away the existing soil to replace it with new soil. Imagine the manpower and fossil fuel needed to accomplish that. What is worse is that the new soil will very soon also be stripped of its fertility if they continue such bare soil cultivation. Some proposed a more scientific approach of testing the soil and adding the lacking nutrients. Our solution – adding organic material – was the easiest and consequently the cheapest. It took a leap of faith from the school to trust a bunch of young people with a stupidly simple solution. We thank them for that.

First Things First – Green Manuring

We decided to start the restoration by growing a round of green manure. Green manure sounds like fresh and wet animal manure but it is actually very different and less smelly. It is a technique of growing plants primarily to add nutrients and organic matter into the soil. You can read more here.

Before that, we had to move many tons of compost up to the rooftop to add fertility to the barren soil. A typical contractor would probably use a crane but we chose to use human power. We had a fun and dirty time while getting a tough workout of shoveling, carrying, and dragging!

We laid a pathway using bricks since the planters are too wide. The point is to prevent people from stepping into the growing beds.

We made some compost art along the way.

We spread a thick layer of compost into the beds and sawdust on to the pathways.

Lots of fun doing it with a good bunch of friends.

After spreading the compost, it is time to sow some seeds! We chose a variety of legumes like cow pea, black eye pea, mung bean, red bean, and soy bean. Legumes help to fix nitrogen which is usually lacking in tropical soil. We also thought that they would be suitable for the hot and sunny rooftop. They grow vigorously and would be able to generate a lot of organic material in a short time. Finally, the heavy rainfall from the upcoming Northeast monsoon would only aid us in our quest.

An assortment of nitrogen-fixing legumes waiting to do their job!

Densely sowed onto the compost.

Colorful magic beans.

Finally, before we leave the beans to do their magic, we did not forget to mulch. Mulching is essential to protect the soil from the harsh elements on the rooftop. Over here, we used the fiber from coconut husks. We like using waste materials.

Just a thin layero f mulch to allow the legumes to grow through.

It looks very brown, at least for now…

How are the legumes going to fare? More to come so keep posted…

Read other posts about Project Spectra here.