The Action of Bacteria on the Soil

Decomposition

• Plants use sunlight to create food but rely on their root systems to provide them with essential minerals and nutrients. Plant roots take in nutrients from soil but not all nutrients are available for plant uptake. Compost and other organic matter found in soil must undergo decomposition in order to unlock essential nutrients that plants need for survival. Bacteria works with other microbes to perform decomposition. In some circumstances bacteria digest organic matter decomposing it into both organic and inorganic compounds. Organic compounds are stored in soil for use by other microbes as well as by earthworms or other soil inhabitants.

Immobilization and Mineral Transformation

• Protozoa and other microbes create sulfur, ammonium and nitrites from organic matter. These inorganic compounds are found in soil. Soil bacteria, called chemotrophs, either store inorganic materials within their cells or break down inorganic compounds into essential minerals ready for plant uptake. When bacteria stores inorganic materials within its cells, they are performing an action known as immobilization. When bacteria processes inorganic compounds into inorganic minerals available for plant uptake, they are performing an action known as mineral transformation.

Nitrogen Cycle

• Nitrogen is found in the air, in raindrops, in compost and worm castings. Fertilizers contain high amounts of nitrogen because the nutrient is essential to plant growth. Plants rely on the nitrogen cycle to process nitrogen into usable nitrates. Bacteria are an essential part of the cycle. Bacteria convert organic nitrogen compounds into plant-usable ammonium and nitrate.

Considerations

• Bacterial activity increases when temperatures are consistently warm and when moisture is present. Decomposition occurs rapidly in the the Southeastern United States and other high humidity, high heat areas. Rapid decomposition limits the amount of organic matter in soil -- making nutrient storage difficult.

  Bacteria are an important food source for both microbial life, such as protozoa, as well as large earthworms and other soil-dwelling creatures. Earthworms eat bacteria and through the digestive process excrete organic material that increases a soil's tilth.