AGR405 Soil Fertility Management Final
Examination Questions and Answers
Verified Solutions 2026/2027
1. What measure quantifies a soil's ability to hold and exchange positively charged
nutrient ions?
A. Anion Exchange Capacity (AEC)
B. Cation Exchange Capacity (CEC)
C. Electrical Conductivity (EC)
D. Base Saturation Percentage
Rationale: Cation Exchange Capacity measures total negative charges on soil clay and
organic matter surfaces that retain nutrient cations like Ca2+, Mg2+, and K+.
2. What biological nitrogen fixation relationship occurs between legume roots and
specific soil bacteria?
A. Free-living Azotobacter fixation
B. Symbiotic Rhizobium infection forming root nodules
C. Mycorrhizal fungal endosymbiosis
D. Actinorhizal Frankia associations
Rationale: Rhizobium bacteria infect legume roots to form functional nodules, converting
atmospheric N2 gas into ammonium in exchange for plant photosynthesates.
3. Which liming material neutralizes soil acidity while providing both calcium and
magnesium?
A. Calcitic limestone (CaCO3)
B. Dolomitic limestone [CaMg(CO3)2]
C. Gypsum (CaSO4·2H2O)
D. Calcium chloride (CaCl2)
Rationale: Dolomitic limestone contains magnesium carbonate alongside calcium carbonate,
making it the preferred liming agent for acidic, low-magnesium soils.
Examination Questions and Answers
Verified Solutions 2026/2027
1. What measure quantifies a soil's ability to hold and exchange positively charged
nutrient ions?
A. Anion Exchange Capacity (AEC)
B. Cation Exchange Capacity (CEC)
C. Electrical Conductivity (EC)
D. Base Saturation Percentage
Rationale: Cation Exchange Capacity measures total negative charges on soil clay and
organic matter surfaces that retain nutrient cations like Ca2+, Mg2+, and K+.
2. What biological nitrogen fixation relationship occurs between legume roots and
specific soil bacteria?
A. Free-living Azotobacter fixation
B. Symbiotic Rhizobium infection forming root nodules
C. Mycorrhizal fungal endosymbiosis
D. Actinorhizal Frankia associations
Rationale: Rhizobium bacteria infect legume roots to form functional nodules, converting
atmospheric N2 gas into ammonium in exchange for plant photosynthesates.
3. Which liming material neutralizes soil acidity while providing both calcium and
magnesium?
A. Calcitic limestone (CaCO3)
B. Dolomitic limestone [CaMg(CO3)2]
C. Gypsum (CaSO4·2H2O)
D. Calcium chloride (CaCl2)
Rationale: Dolomitic limestone contains magnesium carbonate alongside calcium carbonate,
making it the preferred liming agent for acidic, low-magnesium soils.
