Free Soil Science MCQs with Answers

• A. Frankia
• B. Nitrobacter
• C. Pseudomonas
• D. None of the above

Explanation: Nitrobacter oxidizes nitrite (NO₂⁻) to nitrate (NO₃⁻), completing the second stage of nitrification.

• A. None of the above
• B. Lithoshpere
• C. Atmoshpere
• D. Rhizoshpere

Explanation: The rhizosphere is the narrow zone of soil directly influenced by and in contact with plant roots.

• A. Zero charge at surface
• B. All the covalent bonds
• C. All are ionic bond
• D. None of the above

Explanation: The point of zero charge is the pH at which a soil colloid or mineral surface has zero net electrical charge.

• A. Mo
• B. Al
• C. Fe
• D. All the above

Explanation: Aluminium is the most abundant metal in the Earth's crust and can become toxic to plants in strongly acidic soils.

• A. Solid and gases
• B. CO2 & N
• C. Solid and liquid
• D. None of the above

Explanation: Particulate matter is a mixture of suspended solid particles and liquid droplets in the air.

• A. Acid rains
• B. Hair disease
• C. Mental disease
• D. Sleepy feelings

Explanation: Nitrogen oxides released into the atmosphere react with water and oxygen to form nitric acid, contributing to acid rain.

• A. Reduction
• B. Denitrification
• C. Oxidation
• D. None of the above

Explanation: Denitrification is the microbial reduction of nitrate, commonly through nitrite, to gaseous nitrogen forms such as N₂ and N₂O under…

• A. Both a & b
• B. Water to acid
• C. Acid to water
• D. none

Explanation: Always add acid slowly to water because dilution releases heat, and water added to concentrated acid can boil suddenly and splatter…

• A. NH3OAC
• B. Both b & c
• C. NH4AOC
• D. NH4OAC

Explanation: Ammonium acetate consists of NH₄⁺ and acetate, CH₃COO⁻, giving the formula NH₄OAc, also written CH₃COONH₄.

• A. Smectite
• B. Quartz
• C. Gypsum
• D. All the above

Explanation: Quartz is the most abundant silica mineral in many soils because it is highly resistant to weathering.

• A. Solubor
• B. Boric acid
• C. All the above
• D. Borax

Explanation: Boron deficiency can be corrected with several boron fertilizers, including Solubor, boric acid and borax.

• A. Sedimentary rocks
• B. All the above
• C. Alluvial rocks
• D. Igneous rocks

Explanation: Igneous rocks form when molten magma or lava cools and solidifies. Sedimentary rocks instead develop from deposited and cemented…

• A. Eolian
• B. Colluvial
• C. Alluvium
• D. Regolith

Explanation: Material transported and deposited by wind is termed eolian, also spelled aeolian.

• A. Seepage
• B. Soil contamination
• C. Soil erosion
• D. All the above

Explanation: Soil erosion is the removal or wearing away of land-surface material by agents such as wind, water and ice.

• A. Neutral
• B. Acidic
• C. Alkaline
• D. None of the above

Explanation: Na2CO3 is sodium carbonate, a salt of a strong base and a weak acid, so its solution is alkaline.

• A. Desodication
• B. Sodication
• C. Degradation
• D. Salininzation

Explanation: Salinization is the accumulation of soluble salts in the soil root zone, often caused by inadequate drainage or evaporation in arid areas.

• A. Mho's scale
• B. pH scale
• C. Foot scale
• D. None of the above

Explanation: Mineral hardness is measured by the Mohs scale, which ranks minerals from talc at 1 to diamond at 10.

• A. Platy
• B. Massive
• C. Granular
• D. Both b & c

Explanation: A massive soil structure has no visible aggregation, so the soil appears as a single coherent mass.

• A. Lysimeter
• B. Tensiometer
• C. Barometer
• D. Piezometer

Explanation: A piezometer measures positive water pressure or pressure head, typically in saturated soil.

• A. 2650 Kg m-3
• B. 2550 Kg m-3
• C. 2750 Kg m-3
• D. None of the above

Explanation: The particle density of ordinary mineral soil is approximately 2.65 g cm−3, equivalent to 2650 kg m−3.