Understanding Soil Composition and Organic Matter

Soil is a complex mixture that includes mineral particles, water, air, and organic matter. The organic matter in soil comes from the remains of plants and animals. When these organisms die, they decompose over time.

Identifying the Decayed Remains

The question asks for the term that describes the decayed remains of living organisms found in soil. Let's look at the options provided:

• Minerals: Minerals are inorganic substances that come from rocks. While soil contains minerals, they are not the decayed remains of living organisms.
• Biosphere: The biosphere is the part of the Earth where life exists, including land, water, and air. It's a broad term for living organisms and their environment, not specifically decayed matter in soil.
• Saline Soil: Saline soil is soil that has a high concentration of soluble salts. This property is related to the mineral content and moisture, not directly to the decayed organic matter.
• Humus: Humus is dark-colored, stable organic matter that results from the decomposition of plant and animal remains in soil. It is highly decomposed material and is very important for soil fertility and structure.

The Role of Humus in Soil

Based on the definition, humus is precisely the decayed remains of living organisms in soil. It forms through a process called humification, where microorganisms break down organic materials like dead leaves, roots, and animal waste.

Humus is crucial for healthy soil because it:

• Improves soil structure, making it easier for water and air to penetrate.
• Increases the soil's ability to hold water.
• Provides essential nutrients for plants.
• Supports a diverse population of beneficial soil organisms.

Therefore, the decayed remains of living organisms in soil are called humus.

Conclusion on Soil Composition

The term that specifically refers to the decayed remains of living organisms within the soil is humus. This organic component is vital for the health and productivity of the soil ecosystem.

The final answer is Humus.

Revision Table: Soil Components

Additional Information: Humification and Decomposition

Humification is a slow process that occurs after initial decomposition. Decomposition involves breaking down fresh organic matter into simpler substances. Humification is the further breakdown of this organic material into stable, complex organic compounds that form humus.

Different factors affect the rate of decomposition and humification, including:

• Temperature: Warmer temperatures generally speed up decomposition.
• Moisture: Sufficient moisture is needed for microbial activity.
• Aeration: Oxygen is required by most decomposer organisms.
• Type of organic material: Materials like leaves break down faster than wood.
• Soil pH: pH levels affect the activity of decomposer organisms.

Humus persists in the soil for a long time and is an important indicator of soil health and fertility.