How Compost Works

To understand how compost works, we must first understand what compost is…

Compost – noun

1. The product resulting from the controlled biological decomposition of organic material that has been sanitized through the generation of heat and stabilized to the point that it is beneficial to plant growth.

And how is compost produced?

(From the US Composting Council) Compost is produced through the activity of aerobic (oxygen requiring) microorganisms. These microbes require oxygen, moisture, and food in order to grow and multiply. When these factors are maintained at optimal levels, the natural decomposition process is greatly accelerated. The microbes generate heat, water vapor, and carbon dioxide as they transform raw materials into a stable soil conditioner. Active composting is typically characterized by a high-temperature phase that sanitizes the product and allows a high rate of decomposition, followed by a lower-temperature phase that allows the product to stabilize while still decomposing at a lower rate. Compost can be produced from many “feedstocks” (the raw organic materials, such as leaves, manures or food scraps).

So, compost is what’s left over after organic material has been broken down through microbial decomposition.  The process requires a balanced ratio of C:N, moisture, and aeration (oxygen). Done right, temperatures should reach between 130 and 150 degrees Fahrenheit which is sufficient to sanitize the finished product.

Now that we know what compost is and how it’s produced…

How does compost work in the garden?

First and foremost, compost is an indispensable soil amendment. The organic material in compost makes it valuable as a soil structure conditioner, loosening compacted soils and binding loamy soils. Good soil structure is important for drainage, water retention, aeration, root growth and microbial activity. It also introduces natural micro and macro-nutrients to the soil that plants need to grow and be healthy. Active compost introduces a host of beneficial microbes to your garden soil as well improving the soil-food-web environment.

Finished compost often has very balanced nutrient content making it an ideal fertilizer for our garden plants. Because of the inherent moisture content, good structure and microbial life, those nutrients are extremely bioavailable. The nutrient impact can be made even more powerful by making a compost tea from the finished compost.

As a side effect of using compost to create a well-balanced, healthy soil and nutrient-dense plant fertilizer we are fighting off pests as well. Good bacteria proliferating in well-aerated soil crowds out bad bacteria that could damage our plants. Healthy plants have the strength to defend against bad bacteria, molds, fungi and some small invasive pests that prey on unhealthy plants.

In short, good active compost is key in creating a strong, healthy environment for our garden plants to thrive.