Free Soil Science MCQs with Answers

• A. Air
• B. Wind
• C. Water
• D. All the above

Explanation: The sandy, dry landscapes of Thal and Cholistan are especially prone to wind erosion, which moves loose soil particles by saltation and…

• A. Hydrometer
• B. Spectrophotometer
• C. Flame photometer
• D. All the above

Explanation: A flame photometer measures sodium and potassium by detecting the characteristic light emitted by their excited atoms.

• A. Halophytes
• B. Glycophytes
• C. Xerophytes
• D. All the above

Explanation: Halophytes are plants adapted to saline soils or salty water, often through salt exclusion or storage mechanisms.

• A. 5.0 m ha
• B. 6.3 m ha
• C. 12.3 m ha
• D. 10.5 m ha

Explanation: Pakistan has commonly been reported to have about 6.3 million hectares of salt-affected soils.

• A. SO4
• B. HCO3
• C. Cl-
• D. None of the above

Explanation: Cyclic salts are carried from oceans through the atmosphere and are therefore dominated by chloride, along with sodium.

• A. None of these
• B. Mg & Ni
• C. Cu & Ni
• D. Fe & Ni

Explanation: The Earth's core is composed predominantly of iron with a significant amount of nickel, with smaller quantities of other elements.

• A. None of the above
• B. O3 + O
• C. O2 O
• D. O2 + O =O3

Explanation: An oxygen molecule combines with an oxygen atom to form ozone: O₂ + O → O₃.

• A. Negative soil water potential
• B. Hydraulic conductivity
• C. Hydraulic potential
• D. All the aboveGeology

Explanation: pF is the logarithm of soil-water suction, commonly used to express negative soil-water potential.

• A. Saline soil
• B. Sodic soil
• C. Acidic soil
• D. None of the above

Explanation: A soil with an exchangeable sodium percentage above 15 is classified as sodic because excessive exchangeable sodium damages soil structure…

• A. Normal
• B. Molal
• C. Molar
• D. None of the above

Explanation: A solution containing one gram molecular weight of a substance per litre is one molar, or 1 M.

• A. Non-expending
• B. Expending
• C. None of the above
• D. None or little expending

Explanation: The least-expanding clay minerals are described as non-expanding or only slightly expanding; kaolinite is the standard example.

• A. Between 7.5 to 8.5
• B. 8.5
• C. None of the above

Explanation: Many productive agricultural soils in Pakistan are slightly to moderately alkaline, commonly falling around pH 7.5 to 8.5.

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

Explanation: Sodium carbonate hydrolyses in water to produce hydroxyl ions, making its solution alkaline.

• A. 3-15 meq/100g CEC
• B. 40 meq/100g CEC
• C. 50 meq/100g CEC
• D. None of the above

Explanation: Kaolinite is a 1:1 clay mineral with low permanent charge and consequently a low cation-exchange capacity, commonly about 3–15 meq per 100…

• A. Capillary
• B. Hydroscopic
• C. Available
• D. Gravitational

Explanation: A hygroscopic material absorbs moisture directly from atmospheric air, as many salts and fertilizers do.

• A. RSC
• B. SAP
• C. EC
• D. pH

Explanation: A buffer contains a weak acid and its conjugate base, or the corresponding basic pair, so it resists sudden changes in hydrogen-ion…

• A. <7
• B. >7
• C. >7.0
• D. 8.5

Explanation: A soil is classified as acidic when its pH is below 7, because hydrogen-ion activity exceeds hydroxyl-ion activity.

• A. 60
• B. 80-90
• C. 50-70

Explanation: Phosphorus deficiency is widespread in Pakistan because many soils fix phosphate, especially calcareous soils, making it unavailable to…

• A. 0.4 4.0 dsm-1
• B. 0.4dsm-1
• C. >4dsm-1

Explanation: A saline soil has an electrical conductivity of the saturation extract greater than 4 dS m⁻¹ at 25°C.

• A. Less than 7
• B. Neutral
• C. Greater than 7
• D. Basis

Explanation: Coniferous forest litter decomposes to form organic acids, so these soils are generally acidic and have a pH below 7.