The Secret Life of Organisms in the Soil

A single teaspoon of healthy soil can contain up to a billion beneficial bacteria. Life underground is made up of a diversity of organisms working together to help grow healthy plants. Feeding these microorganisms in soil can unlock an underground workforce to help grow healthier plants.

Structure of Healthy Soil

Healthy soil smells and feels like the loose moist soil that is found underneath a layer of decaying leaves in a forest. It is rich in organic matter and contains approximately 24% air, 25% water, 45% minerals, 3-5% humus and up to 1% living organisms. It is the latter 1% that is responsible for keeping the soil well aerated, able to retain water and full of nutrients.

The Soil Food Web

The underground community of organisms was called the ‘Soil Food Web’ by Dr. Elaine Ingham, a soil specialist in Oregon, US. In an interview with the author, she said that the soil food web is responsible for developing good soil structure by sticking little pieces of soil together and breaking down large clods. This process enhances the movement of air and water in the soil, which are both essential elements for the health of plants. Good soil structure allows water to drain from too wet soil and helps soil to hold water when soils start to dry out.

How Does the Soil Food Web Work?

Soil food web organisms feed on plant residues and manure in the soil as well as on each other, breaking their food down and capturing the nutrients. They hold these nutrients (for example nitrogen, calcium, iron) in their bodies thereby preventing nutrient loss through leaching.

These organisms make the nutrients available to plants when and where the plants need them, in the form and amounts the plants need. Completing the cycle, plants excrete materials from their roots that are additional food for the soil organisms.

In the process of feeding on plant materials and each other, these organisms also produce hormones that plants need, and consume or break down pollutants, like pesticides in the soil. The soil food web also suppresses disease-causing organisms and other pests through various means like out-competing them for food or altering the soil conditions so they cannot thrive.

What are the Benefits of Having Healthy Soil Life?

Healthy soil life has many benefits for gardens, small holdings and farms. The underground life consists of organisms such as bacteria, fungi, protozoa (tiny single celled organisms), nematodes (microscopic unsegmented worms), arthropods (like mites, millipedes and dung beetles) and earthworms. Each of these organisms has a unique role in the soil food web and they work together to give the gardener or grower the following benefits:

• Reduced fertilizer use because a healthy food web efficiently stores and makes nutrients available to plants.
• Soil organisms hold nitrogen in the rooting zone, thus preventing leaching of this important nutrient into the groundwater.
• Soil structure improves, enhancing the water holding capacity of the soil making more water available to the plants.
• Soil organisms stabilize the soil structure, minimizing topsoil loss due to water and wind erosion.
• Soil organisms work together to prevent plant diseases and pests, thus leading to reduced pesticide use.

The organisms in the soil food web are like an underground workforce, toiling endlessly to provide an environment where plants can thrive. Gardeners and farmers will do well to make sure that their soil is full of these beneficial creatures.

Sources:

The Soil Food Web Laboratory Website accessed 10 December 2009