Backyard Bacteria: Breaking it Down

What Exactly Do Soil Bacteria Do?

Bacteria grow in many different microenvironments and enjoy specific niches in the soil. Bacteria populations expand rapidly and the bacteria are more competitive when easy to digest simple sugars are readily available around in the rhizosphere (“living” area of soil). Roots, dead plant debris, and simple sugars are abundant in this region. About 10 to 30 percent of the soil microorganisms in the rhizosphere are actinomycetes, depending on environmental conditions (Sylvia et al., 2005).

Many bacteria produce a layer of sugars or proteins that coats the surface of soil particles. These substances play an important role in cementing sand, silt and clay soil particles into stable microaggregates that improve soil structure. Bacteria live around the edges of soil mineral particles, especially clay and organic residues. 

Bacteria are important in producing sugars that cement sand, silt and clay particles together to form microaggregates and improve soil structure (Hoorman, 2011). Bacteria do not move very far in the soil, so most movement is associated with water, growing roots or catching  a ride with other soil members like earthworms, ants, spiders, etc. (Lavelle & Spain, 2005).  

In general, most soil bacteria do better in neutral pH soils that are well oxygenated. Bacteria provide large quantities of nitrogen to plants and nitrogen is often lacking in the soil. Many bacteria secrete enzymes in the soil to make phosphorus more soluble and plant available.

The Original Survivors

Bacteria dominate over fungi in tilled or disrupted soils because the fungi prefer more acidic environments without soil disturbance. Bacteria also dominate in flooded fields because most fungi do not survive when oxygen is scarce.

 Bacteria can survive in dry or flooded conditions due to their small size, high numbers, and their ability to live in small spaces within the soil where environmental conditions may be favorable. Once the environmental conditions around these microsites become more favorable, the survivors quickly expand their populations (Dick, W., 2009). Protozoa tend to be the biggest predators of bacteria in tilled soils (Islam, 2008).

Without bacteria, new plant populations and communities struggle to survive or even exist. Bacteria change the soil environment so that certain plant species can exist and proliferate. When new soil is forming, certain photosynthetic bacteria start to colonize the soil, recycling nitrogen, carbon, phosphorus, and other soil nutrients to produce the first organic matter.

Bacteria = Soil Health

 A soil that is dominated by bacteria usually is tilled or disrupted and has higher soil pH and nitrogen available as nitrate, which is the perfect environment for low successional plants we refer to as weeds (Ingham, 2009).

As the soil is disturbed less and plant diversity increases, the soil food web becomes more balanced and diverse, making soil nutrients more available in an environment better suited to higher plants. Diverse microbial populations with fungus, protozoa and nematodes keep nutrients recycling and keep disease-causing organisms in check.

Microbia labs can assess your soil and compost samples to identify valuable and potentially harmful strains of bacteria. Knowing means growing!

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