Question

What is organic matter in soil? A) leaching C) horizon B) humus D) profile

Short answer

B) Humus

Step-by-step solution

Understand the Term

The question asks about 'organic matter in soil.' Organic matter in soil primarily consists of decomposed plant and animal residues, living organisms, and carbon-rich substances.

Analyze the Options

The options given are A) leaching, B) humus, C) horizon, and D) profile. We need to identify which of these terms best fits the description of organic matter in soil.

Evaluate Each Option

Let's break down each option: - A) 'Leaching' refers to the process of washing nutrients out of the soil, which doesn't describe organic matter itself. - B) 'Humus' is the organic component of soil, composed of decomposed plant and animal material and rich in the nutrients necessary for plant growth. - C) 'Horizon' refers to a layer of soil, not the organic material in it. - D) 'Profile' describes the vertical section of soil layers but does not specifically refer to organic material.

Identify the Correct Option

Based on the analysis, 'humus' is defined as the organic matter in the soil composed of decayed plant and animal matter. Therefore, B) humus clearly fits the description of organic matter in soil.

Key concepts

Humus

Humus is a crucial component of soil and is essentially decomposed organic material. When plants and animals die, they decompose and transform into a rich, dark substance known as humus.
This process increases the nutrient content of the soil. Humus is rich in nutrients like nitrogen, phosphorus, and potassium, essential for plant growth. It is also important because:

• It improves soil structure by binding smaller particles into aggregates. This allows for better water retention and aeration.
• It provides a habitat for microorganisms that contribute to soil fertility.
• It acts as a buffer for pH changes in the soil.

Integrating humus into soil management practices can dramatically boost soil health and plant productivity.

Soil Horizons

Soil horizons are distinct layers found in a soil profile, each with unique characteristics and properties. The formation of soil horizons is influenced by several factors such as climate, organisms, and topography.
Typically, a full soil profile comprises several horizons. These main horizons are:

• O Horizon: This is the organic layer made up of decomposed leaves, plants, and other organic materials.
• A Horizon: Also known as topsoil, it's rich in organic material and where most plant roots grow.
• B Horizon: A subsoil that accumulates minerals leached from the topsoil.
• C Horizon: Consists of weathered parent material from which soil develops.
• R Horizon: The underlying bedrock.

Understanding these horizons is critical for effective farming and gardening, as it helps determine soil quality and suitability for different plants.

Leaching

Leaching is a natural process in which water-soluble nutrients are washed out from the soil, often moving downwards through the soil profile. It occurs primarily due to rainfall or irrigation, and its intensity depends on several factors like soil texture and rainfall intensity.
While leaching can lead to nutrient depletion in the soil, making it a challenge for agriculture, it also helps in:

• Removing harmful substances like excess salts from the soil.
• Helping redistribute nutrients within a soil profile.

Avoiding excessive leaching preserves soil fertility. Practices such as applying fertilizers at the right time and using organic compost can minimize the loss of nutrients due to leaching.

Soil Profile

A soil profile is a vertical section that displays the different layers, or horizons, in soil from top to bottom. Each soil profile is unique depending on the type of soil, climate, and organic activity in the area.
Studying soil profiles allows researchers and farmers to:

• Assess the soil's development, quality, and fertility.
• Make informed decisions about crop selection and soil management.

By understanding a soil profile, one can appreciate its complex structure and its impact on plant growth and land use decisions. Each layer in the profile tells a story about the soil's history and its current capabilities.