Question

Q. Which of the following are major factors that control the formation of soils?

Select the correct answer using the codes given below:

• A. 1, 2, 4 and 5 only
• B. 2, 3 and 5 only
• C. 1, 3 and 4 only
• D. 1, 2, 3, 4 and 5

Answer 1

The correct option is D 1, 2, 3, 4 and 5

Explanation:

The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time.

Relief:

• The relief is the most important factor for soil formation in places with steep slopes like the hilly regions, edges of plateaus, etc. Soil erosion on barren slopes is rampant and hinders soil formation.
• Example: Chambal ravines and higher reaches of the Himalayas where there is minimal or no forest cover.

Parent material:

• The rocks from which soils are formed are called parent materials. In most cases, the parent material determines the colouration, mineral composition and texture of the soil.
• Example: Volcanic outburst over a vast area of Peninsular India many hundred million years ago gave rise to Deccan Traps. Consequently, the weathering of these rocks has given rise to ‘regur’ or black cotton soil.

Climate:

• Temperature and rainfall are the most important factors in soil formation.
• Hot summer and low rainfall develop black soil as is found in some parts of Tamil Nadu irrespective of the parent rock.
• The laterite soils develop in areas with high temperatures and high rainfall.

Natural Vegetation:

• Natural vegetation reflects the combined effects of relief and climate.
• The formation and development of soil are very much influenced by the growth of vegetation.
• The decayed leaf material adds much-needed humus to soil thereby increasing its fertility.

Time:

• Time is the fifth factor in soil formation. Over time, vegetation and climate act on parent material and topography. Older soils differ from younger soils because they have had longer to develop