Soil Organic Matter

Definition

Soil organic matter refers to the organic component of soil, primarily composed of decomposed plant and animal materials, as well as microbial biomass. It plays a crucial role in enhancing soil fertility, structure, and water retention, while also influencing nutrient cycling and interactions between organic and inorganic substances within the soil ecosystem.

5 Must Know Facts For Your Next Test

1. Soil organic matter typically comprises about 1-6% of the total soil mass but is vital for soil health and productivity.
2. It contributes to soil structure by promoting aggregation, which helps improve aeration and water infiltration.
3. Decomposing organic materials release essential nutrients like nitrogen, phosphorus, and sulfur, making them available for plant uptake.
4. The presence of soil organic matter enhances the soil's ability to sequester carbon, playing a significant role in mitigating climate change.
5. Organic matter serves as a habitat for beneficial microorganisms, which are essential for various soil processes, including nutrient cycling and disease suppression.

Review Questions

• How does soil organic matter influence nutrient availability in soils?
  • Soil organic matter influences nutrient availability by breaking down into simpler forms through microbial decomposition, releasing essential nutrients like nitrogen, phosphorus, and sulfur. This process not only increases the nutrient pool accessible to plants but also improves the overall fertility of the soil. As organic matter decomposes, it creates compounds that enhance the retention of nutrients within the soil matrix, making them more readily available for plant uptake.
• Discuss the impact of soil organic matter on soil structure and how this affects water retention.
  • Soil organic matter significantly impacts soil structure by promoting aggregation, which leads to improved pore spaces within the soil. This enhanced structure allows for better aeration and infiltration of water, reducing runoff and erosion. Improved water retention is crucial for maintaining moisture levels during dry periods, benefiting plant growth and overall ecosystem health.
• Evaluate the role of soil organic matter in carbon sequestration and its implications for climate change mitigation.
  • Soil organic matter plays a critical role in carbon sequestration by capturing atmospheric carbon dioxide through plant photosynthesis and storing it in the soil as organic matter. This process mitigates climate change by reducing greenhouse gases in the atmosphere. Maintaining or increasing levels of soil organic matter through practices like cover cropping or reduced tillage can enhance carbon storage potential in soils, providing a natural solution to combat climate change while improving soil health and agricultural productivity.

Related terms

Humus: Humus is the stable, decomposed organic matter in soil that provides essential nutrients and improves soil structure.

Soil Microbiology: Soil microbiology studies the role of microorganisms in soil processes, including the decomposition of organic matter and nutrient cycling.

Cation Exchange Capacity (CEC): Cation exchange capacity is a measure of how well soil can retain and supply cations to plant roots, influenced by the presence of organic matter.