Learning to compost on South Caicos.

By Anna-Handte-Reinecker, Program Assistant, The School for Field Studies, Center for Marine Resource Studies, South Caicos

We often forget to appreciate the soil beneath our feet. Soil, which is a complex combination of organic and inorganic matter, supports life as we know it. Simply put, without soil, neither plants nor animals would be able to survive. For this reason, soil availability and quality are tightly linked to food security around the world.

Soil basics

Soil is a complex combination of organic and inorganic matter.

To understand what makes up a healthy soil we must look at its components. There are three major types of soil particles—clay, silt and sand—differing in the sizes of the individual particles. Clay contains the smallest particles, followed by silt and then sand. These size differences create soils that have varying amounts of space between each particle; these gaps are called pore spaces. Pore spaces govern the amount of water, air and nutrients each soil type can retain. This, in turn, controls the types of plants and organisms the soil can support. The ratios of these particles within a soil determine the kind of soil it is. For example, the soil type called “loam” is made up of about 80% silt, 50% sand and 15% clay.

Soil is also incredibly important for filtering and retaining water. It is estimated that 1 cubic meter of certain soils, when fully saturated, can hold up to 600 liters of water. This means that even during times of less rainfall, plants are able to get the water they need from soil. Furthermore, the water retention of soil can reduce the amount of flooding in an area.

In addition to particle size, an important element of soil is microbial presence. A generous number of bacteria is an integral part of a healthy soil fit to grow a garden. According to the United States Department of Agriculture, “A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria.”

Bacteria often get a bad reputation for being dangerous and causing infections. However, not all bacteria are detrimental. In fact, many of the antibiotics we use today are derived from bacteria found in soil. We even have bacteria that live in our gut and allow us to digest food!

Soil and climate change
Healthy soil is an integral component of regulating global climate. Global warming is driven by greenhouse gases in the atmosphere. Greenhouse gases contribute to global warming as they remain in our atmosphere and reflect light waves back onto the earth, increasing global temperatures. According to the US Environmental Protection Agency, carbon dioxide makes up a whopping 82% of all greenhouse gas emissions in the US (data from 2017). Soil is an important “carbon sink,” meaning that when carbon enters the soil through decomposition of organic material, it remains there for long periods of time. The only carbon sink that is larger than soil are our oceans. Soil as a carbon sink is essential because it keeps carbon out of the atmosphere and reduces global warming due to greenhouse gases. Today we are facing unprecedented soil erosion around the world, often due to human development. As soil erodes, so does one of our essential defenses against climate change.

How to make soil

SFS Students and community members in South Caicos construct a hot compost heap.

So now that we know how important soil is, how can we make our own, particularly in places where healthy soil is scarce?

People have invented a way of expediting the natural processes of decomposition in order to create soil for use on farms. Composting is the process of fertilizing land with decaying organic material. Incredibly, scientists have determined that humans have used “reclaimed organic matter for farming” since at least the stone age! By now, there are many different types of composting methods to accommodate different needs.

In the TCI, we see a wide variation in soil quality and quantity. From lush green Middle Caicos to arid South Caicos, no two islands are the same. This spring, we at The School for Field Studies on South Caicos were determined to cultivate and grow our own garden and compost. Led by the SFS Environmental Policy Lecturer Dr. Neil Oculi, students and staff worked to create a type of compost called a hot compost.

A hot compost is characterized by the heat it produces as a result of organisms breaking down organic matter. This type of compost relies heavily on proper carbon and nitrogen ratios which in turn speeds up the decomposition of organic materials. To start our hot compost, we began by making an enclosure that would keep out any unwanted horses and donkeys. We then began to collect the materials that would make up the base of our compost heap.

The four ingredients were nitrogen, carbon, water and air. Green materials such as grass clippings and coffee grounds are high in nitrogen, whereas brown materials such as dead leaves and newspapers are high in carbon. Our aim was to have a 30:1 carbon to nitrogen ratio in order to facilitate the fastest possible decomposition of organic materials. In general, having a 2:1 ratio of green to brown materials will allow the compost to get close to that 30:1 carbon to nitrogen ratio.

We layered brown and green materials into a heap 3 feet wide and 3 feet high. Next, toilet paper rolls were added to allow for aeration. Then, in order to maintain the compost, we mixed the heap weekly to promote aeration and watered it every few days to prevent it from drying out. Both lack of air and water can cause beneficial organisms and bacteria to die, which we don’t want! If a compost heap is constructed correctly, the heap’s core temperature increases to about 54–60ºC. After a few weeks we observed that our hot compost had reached the optimum temperature and was successfully breaking down the organic materials. The plan is to take this soil and use it in our garden to grow herbs and vegetables.
Students and staff also worked closely with the Marjorie Basden High School to begin construction on a Hügelkutur and community garden. A Hügelkutur is a different type of compost that consists of a mound with wood in the center and compostable materials on top. A benefit to the Hügelkultur is that it requires less water than the hot compost.

Another great composting option for those with less space is a vermiculture. To create a personal vermiculture, all that you need is a large bin with a lid. You will need to make multiple holes in the bottom, sides and lid of the bin to allow for drainage and aeration. The next step is to put a layer of soil or compost at the bottom of the bin about 5 cm deep. Lastly, you will need to add 500–1,000 worms, which you can either order online or collect from your yard. After your worms have settled in for a week, you can add vegetable scraps, newspapers, leaves and coffee grounds for the worms to eat.

You also want to make sure that your soil stays moist and you water it regularly. Making these compost heaps were fun and rewarding projects— be inspired to start your own!

For more information, contact SFS Center Director Heidi Hertler, PhD at hhertler@fieldstudies.org.