Fundamentals of Plant Nutrition MCQs Quiz 20

1. Ammonia volatilization is most likely to occur when nitrogen is present as _______ under alkaline and surface-applied conditions

 Nitrate (NO₃⁻)

 Organic nitrogen in stable humus

 Ammonium (NH₄⁺) in equilibrium with NH₃ gas

 Nitrite (NO₂⁻) under anaerobic conditions

2. Soil fertility is best defined as the soil’s inherent capacity to _______, whereas productivity reflects integrated field performance

 Produce maximum economic yield under all conditions

 Supply essential nutrients in adequate amounts and balance

 Retain water irrespective of climatic variation

 Support plant growth independent of management practices

3. Adequate potassium nutrition improves plant resilience primarily by enhancing _______

 Osmotic regulation and activation of stress-responsive enzymes

 Exclusive stimulation of mitotic cell division

 Structural incorporation into chlorophyll molecules

 Direct participation in nitrogen fixation within nodules

4. The primary biochemical role of potassium in plant metabolism is to _______________________

 Directly participate in nitrogenase activity

 Serve as a structural component of nucleic acids

 Form stable complexes in cell wall polymers

 Act as a cofactor activating numerous metabolic enzymes

5. Rate of nutrient diffusion in soil primarily depends on _______

 Concentration gradient

 Soil pH

 Soil temperature

 Light duration

6. Leguminous residues typically have _______ C:N ratio

 Very high

 Low

 Moderate

 Variable but always above 50

7. The primary mechanism by which mycorrhizal fungi improve phosphorus uptake is _______

 Increasing soil pH to solubilize phosphate minerals

 Extending the effective root surface area via hyphal networks

 Enhancing phosphorus fixation in the rhizosphere

 Reducing soil moisture to concentrate available phosphorus

8. Soil texture primarily influences nutrient dynamics through _______

 Water color

 Soil pH only

 Light absorption

 Cation exchange capacity

9. Micropores (<0.08 mm diameter) predominantly contribute to _______ under field capacity conditions

 Rapid gaseous diffusion

 Soil structural instability

 Water retention against gravitational drainage

 Preferential flow of solutes

10. Nutrient fixation in soils refers to _______

 Temporary immobilization by microbes

 Transformation into unavailable mineral forms

 Conversion into gaseous forms

 Leaching beyond the root zone

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