Question

Read the given statements and select the correct option. Statement 1 :Soil serves as a reservoir of essential elements. Statement \(2:\) Soil develops, over the years, through physical and chemical weathering of rocks. (a) Both statements 1 and 2 are correct and statement 2 is the correct explanation of statement 1 . (b) Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1 . (c) Statement 1 is correct and statement 2 is incorrect. (d) Both statements 1 and 2 are incorrect.

Short answer

Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1, so the correct option is (b).

Step-by-step solution

Analyze Statement 1

Evaluate the accuracy of Statement 1. Soil indeed acts as a storage place for essential nutrients needed by plants and other organisms, making it a reservoir of essential elements.

Analyze Statement 2

Assess the accuracy of Statement 2. Soil forms over time from the physical and chemical breakdown (weathering) of rocks and organic matter. This is a well-established scientific fact.

Determine the Relationship Between the Two Statements

Decide if Statement 2 explains Statement 1. The development of soil contributes to its ability to serve as a storehouse for essential elements, however, it does not directly explain why soil acts as a reservoir for essential elements, which has more to do with the ability to retain and release nutrients than with the process of soil formation.

Key concepts

Soil Formation

Understanding soil formation is crucial for comprehending its importance in sustaining life. The process occurs over countless years and is the result of both physical and chemical weathering of rocks, combined with the gradual accumulation of decayed organic material.

Physical Weathering

This refers to the breaking down of rocks through mechanical processes, such as freeze-thaw cycles, which cause rocks to crack and split.

Chemical Weathering

In contrast, chemical weathering involves the alteration of the rock's minerals when exposed to water, air, and organic matter. This can lead to the formation of new minerals and soil particles. Together, these weathering processes contribute to creating the top layer of the Earth's crust wherein plants can take root and grow. The type of soil that forms depends on the parent rock material, climate, topography, and the time available for its development. The presence of microorganisms and plants accelerates this process, further enriching the soil.

Weathering of Rocks

The breakdown of rocks, known as weathering, is fundamental to soil development.

Types of Weathering

There are two main types of weathering that contribute to this process: mechanical and chemical. Mechanical weathering includes physical changes like temperature variations causing expansion and contraction, ultimately fracturing rocks. Water can also play a role when it freezes in cracks and expands, leading to further breaking apart of rock.

Biological Weathering

Additionally, biological weathering occurs when living organisms, such as plant roots, penetrate and break rock material.

As these weathering processes continue, rocks are reduced to smaller and smaller particles, eventually becoming fine enough to mix with organic matter and form soil. The resultant soil retains the characteristics of the original parent rock, influencing its mineral content and pH balance, which are critical for plant nutrients.

Essential Nutrients in Soil

The soil is more than just dirt; it's a complex mixture teeming with life and nutrients. Essential nutrients within the soil are needed for plant growth and development.

Macro and Micronutrients

These include macronutrients like nitrogen, phosphorus, and potassium, which are required in large quantities. Micronutrients, such as iron, manganese, and zinc, are needed in smaller amounts but are just as critical for plant health.

The soil's capacity to hold onto these nutrients and release them to plants is what makes it a 'reservoir of essential elements.' Plants absorb these nutrients from the soil through their roots, making soil quality and composition pivotal to crop yield and the overall health of the ecosystem. Regular soil testing can help identify deficiencies or imbalances in soil nutrients and guide proper fertilization and management practices to maintain soil health and sustainability.