Soil organic matter

Definition

Soil organic matter refers to the organic components of soil, primarily made up of decomposed plant and animal material, as well as microbial biomass. This component plays a crucial role in enhancing soil fertility, improving water retention, and serving as a reservoir for essential nutrients like phosphorus. Understanding soil organic matter is key to recognizing its influence on nutrient cycling and the overall health of soil ecosystems.

5 Must Know Facts For Your Next Test

1. Soil organic matter typically comprises about 3-5% of the total weight of soil but plays a critical role in soil health and fertility.
2. The decomposition of organic matter leads to the formation of humus, which improves soil structure and increases its ability to retain moisture.
3. Soil organic matter acts as a buffer for pH changes and helps in preventing soil erosion by binding soil particles together.
4. It is essential for the storage and availability of nutrients, especially phosphorus, making it a vital component in agricultural productivity.
5. Soil organic matter contributes to carbon sequestration, helping mitigate climate change by storing carbon that would otherwise be released into the atmosphere.

Review Questions

• How does soil organic matter influence nutrient availability in soils?
  • Soil organic matter plays a vital role in nutrient availability by acting as a reservoir for essential nutrients like nitrogen and phosphorus. As it decomposes, it releases these nutrients into the soil in forms that plants can readily absorb. Furthermore, it enhances the cation exchange capacity of the soil, allowing for better retention and exchange of nutrients, thus directly supporting plant growth and ecosystem health.
• Discuss the relationship between soil organic matter and water retention capabilities in soils.
  • Soil organic matter significantly enhances water retention capabilities due to its ability to hold moisture like a sponge. The porous nature of decomposed organic materials allows for improved infiltration and reduces surface runoff. This increased water-holding capacity is crucial for sustaining plant growth during dry periods and contributes to overall soil structure, promoting healthy root development.
• Evaluate the implications of declining soil organic matter levels on agricultural productivity and environmental health.
  • Declining levels of soil organic matter can lead to reduced agricultural productivity due to diminished nutrient availability and poor water retention. This decline often results in increased reliance on chemical fertilizers, which can further degrade soil health over time. Environmentally, lower organic matter levels can lead to increased erosion, loss of biodiversity, and higher carbon emissions, ultimately impacting ecosystem resilience and sustainability.

Related terms

humus: Humus is the dark, organic material in soil that forms from the decomposition of plant and animal matter, contributing to soil fertility and structure.

microbial biomass: Microbial biomass refers to the living organisms within the soil, including bacteria and fungi, which contribute to the breakdown of organic matter and nutrient cycling.

nutrient cycling: Nutrient cycling is the process through which nutrients are transferred between the biotic and abiotic components of the ecosystem, particularly within soil.