Plan the perfect garden with our interactive tool →

What Is Humus Fertilizer?

Comstock/Comstock/Getty Images

Humus is a substance that most people don't give a second thought. Not exactly a fertilizer and not exactly soil, humus is the product of the decomposition of organic materials like leaves and animal waste. Like a fertilizer, humus holds nutrients that plants can use, but releases them slowly over time as it breaks down. It enhances soil quality in a variety of ways.

Creation of Humus

Humus is created when bacteria and other microbial agents in the soil process and break down organic materials. Over successive generations, all the accessible nutrients are utilized by these tiny decomposers and turned into compounds that plants can take in. Humus is a complex material that can take a decade to break down in the soil once it is fully formed.

Several Compounds

The three main components of humus are fulvic acid, humic acid and humin. These substances are complex polymers formed from the modification of decay-resistant materials such as lignin, cellulose and hemicellulose. Humic acid and humin are more resistant to decay than fulvic acid.

Properties of Humus

Humus has specific properties that make it invaluable to the health of plants. The spongy nature of humus helps it to trap and hold water, this particular property also helps to aerate the soil as humus expands and contracts with available water. Humus provides long term storage of essential plant nutrients and leaches them slowly back into the soil.

Soil Additive

Humus is an effective soil additive because of its unique properties. It is especially beneficial in clay soils, where it can serve to break up compaction and create a looser and better draining soil. Humus must be worked into clay soils because it tends to accumulate above the clay level, unlike with other soils.

Garden Guides