Which soil forming factor determines the colour, texture, chemical properties, mineral content and permeability of soil?

Introduction / Context:

This question addresses fundamental soil science, specifically the factors responsible for soil formation and properties. Soil characteristics such as colour, texture, chemical composition, mineral content and permeability are influenced by several factors. The focus here is to identify the factor that directly provides the primary material from which these properties are largely derived.

Given Data / Assumptions:

• Soil formation depends on factors such as parent rock, climate, organisms, relief and time.
• Properties mentioned include colour, texture, chemical nature, mineral content and permeability.
• The options list flora and fauna, time, climate, parent rock and relief.
• The question asks which factor determines these basic soil properties to a large extent.

Concept / Approach:

The parent rock or parent material is the original geological material from which soil develops through weathering. Its mineral composition directly influences the minerals available in the soil and thus many chemical and physical properties. For example, soils derived from basalt differ from those formed on granite in colour, texture and fertility. While climate, organisms, relief and time modify and develop the soil profile, parent rock provides the fundamental mineral framework that governs many of the characteristics listed in the question.

Step-by-Step Solution:

Verification / Alternative check:

Soil science textbooks present the classic list of soil forming factors: parent material, climate, organisms, topography and time. They explain that while all contribute, the parent material exerts strong control over the initial chemical and mineralogical composition. For instance, calcareous parent rocks produce calcareous soils, and iron rich rocks yield reddish soils. Such examples verify that parent rock is the primary determinant of the properties listed.

Why Other Options Are Wrong:

Flora and fauna, which represent living organisms, influence organic matter content and biological activity but do not directly set the original mineral composition of the soil. Time controls the extent of soil development, profile depth and horizon formation, yet the basic mineral framework comes from the parent material. Climate affects weathering rates and some characteristics like leaching, but again relies on the minerals present in the parent rock. Relief or topography influences drainage and erosion patterns, but not the fundamental mineral content. Therefore, although these factors modify soil, they are not the main determinant of all properties listed in the question.

Common Pitfalls:

Students sometimes incorrectly choose climate because rainfall and temperature greatly affect weathering processes. Others may pick flora and fauna thinking of organic matter contributions. However, the question highlights properties such as mineral content and chemical nature, which point strongly towards parent rock. Keeping in mind that parent material is the starting point for soil creation helps avoid confusion.

Final Answer:

The soil forming factor that determines colour, texture, chemical properties, mineral content and permeability is the Parent rock.