Introduction to Soil Science MCQs

1. Which of the following soil textures has the highest cation exchange capacity (CEC)?
(A) Clay
(B) Silt
(C) Sand
(D) Loam

2. Which of the following is the primary factor influencing the rate of weathering of soil minerals?
(A) Organic matter content
(B) Soil pH
(C) Climate
(D) Soil texture

3. In soils, the process of illuviation refers to the:
(A) Removal of material from the soil
(B) Accumulation of materials in the lower soil horizons
(C) Conversion of organic matter into humus
(D) Leaching of nutrients into groundwater

4. Which of the following is a characteristic of acidic soils?
(A) High base saturation
(B) High cation exchange capacity
(C) Low pH value
(D) Rich in calcium and magnesium

5. Which of the following soil properties is most directly influenced by soil organic matter content?
(A) Soil texture
(B) Bulk density
(C) Soil pH
(D) Soil permeability

6. Which clay mineral is most commonly found in temperate soils and has a high shrink-swell capacity?
(A) Kaolinite
(B) Illite
(C) Smectite
(D) Vermiculite

7. What is the primary function of soil microorganisms in the nitrogen cycle?
(A) Absorbing nitrogen from the atmosphere
(B) Converting nitrogen into nitrites and nitrates
(C) Fixing nitrogen into organic matter
(D) Converting ammonium to nitrate

8. Which of the following soil components is most responsible for soil structure development?
(A) Sand
(B) Silt
(C) Clay
(D) Organic matter

9. The process by which water moves through soil due to the force of gravity is called:
(A) Capillary movement
(B) Osmosis
(C) Infiltration
(D) Percolation

10. Which of the following is the most accurate description of the “soil water holding capacity”?
(A) The amount of water retained by the soil after drainage
(B) The volume of water that can be absorbed by the soil during heavy rain
(C) The amount of water available for plant use only
(D) The volume of water retained in the soil after the excess water has drained away, but before permanent wilting point

11. The soil pH of 7 indicates:
(A) Acidic soil
(B) Neutral soil
(C) Alkaline soil
(D) Highly basic soil

12. Which of the following is an example of an anthropogenic soil disturbance?
(A) Soil erosion
(B) Soil compaction due to foot traffic
(C) Leaching of nutrients
(D) Soil salinization due to irrigation

13. Which of the following is the main cause of soil salinization in arid regions?
(A) Excessive irrigation with salty water
(B) High rainfall and leaching
(C) High levels of organic matter
(D) Flooding from nearby rivers

14. Which of the following is the most common cation found in the exchange sites of soil?
(A) Calcium (Ca²⁺)
(B) Magnesium (Mg²⁺)
(C) Sodium (Na⁺)
(D) Potassium (K⁺)

15. Which of the following is NOT a soil-forming factor?
(A) Parent material
(B) Climate
(C) Time
(D) Land use