Soil Organic Matter MCQs Quiz 4

1. The mechanism underlying the priming effect is primarily associated with _______

 Leaching of nutrients

 Physical breakdown of soil aggregates

 Chemical weathering only

 Enhanced microbial activity and extracellular enzyme production

2. Soil organic matter (SOM) improves soil structure by _______

 Promoting aggregate formation and stability

 Reducing water infiltration

 Increasing soil compaction

 Reducing soil porosity

3. Which of the following practices is a primary cause of soil organic matter (SOM) depletion?

 Application of organic amendments

 Cover cropping

 Crop residue retention

 Intensive tillage

4. The cation exchange capacity (CEC) of soil increases with Soil Organic Matter primarily because of _______

 Mineral particle size only

 Soil water content

 Positive surface charges

 Negative functional groups

5. ______________ is considered as the largest terrestrial carbon pool

 Soil

 Atmosphere

 Oceans

 Vegetation

6. In soils, iron (Fe) and aluminum (Al) oxides stabilize soil organic matter (SOM) primarily via _______

 Ligand exchange

 Physical trapping only within large pores

 Indirect stimulation of microbial activity

 Weak van der Waals bonding

7. In soil science, the “priming effect” refers to _______

 Stabilization of soil organic matter (SOM) against decomposition

 Complete inhibition of microbial activity due to toxic compounds

 A change in the decomposition rate of native Soil Organic Matter following the addition of fresh organic inputs

 Conversion of inorganic carbon (e.g., CO₂) into organic carbon via microbial fixation

8. Root-derived carbon in soils is generally _______

 More stable due to stronger interactions with soil minerals

 Less stable than surface litter inputs

 Inorganic in nature

 Rapidly lost through leaching

9. In soil science and biogeochemistry, the acronym DOC stands for _______

 Dry organic carbon

 Dynamic organic carbon

 Dissolved organic carbon

 Decomposed organic carbon

10. In soil biogeochemistry, the Q₁₀ coefficient represents _______

 Rate of carbon input from plant litter

 Change in soil pH per 10°C increase

 Gravimetric moisture content of soil

 Temperature sensitivity of a biological process e.g., SOM decomposition

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