Agronomy Soil Science and Fertility 2 — Questions and Answers
Question 1: Soil organic matter improves soil structure primarily by doing what?
- Increasing bulk density
- Promoting aggregate formation (Correct answer)
- Raising soil pH
- Reducing microbial activity
Correct answer: Promoting aggregate formation
Organic matter binds soil particles into aggregates, improving aeration, water infiltration, and tilth.
Question 2: Which micronutrient deficiency commonly appears as interveinal chlorosis on young leaves?
- Iron (Correct answer)
- Manganese
- Zinc
- Boron
Correct answer: Iron
Iron deficiency causes interveinal chlorosis on young leaves because iron is immobile in plants.
Question 3: What does the term 'base saturation' refer to in soil science?
- Percentage of CEC occupied by base cations (Correct answer)
- Total amount of organic matter
- Ratio of sand to clay
- Depth of the A horizon
Correct answer: Percentage of CEC occupied by base cations
Base saturation is the percentage of a soil's CEC occupied by basic cations such as Ca²⁺, Mg²⁺, K⁺, and Na⁺.
Question 4: Which soil order is commonly found in the Corn Belt and is highly productive for agriculture?
- Oxisol
- Mollisol (Correct answer)
- Aridisol
- Spodosol
Correct answer: Mollisol
Mollisols have thick, dark, organic-rich A horizons and high natural fertility, making them ideal for corn and soybean production.
Question 5: Liming a soil primarily corrects which soil problem?
- Low phosphorus levels
- Excessive acidity (Correct answer)
- Poor drainage
- High salinity
Correct answer: Excessive acidity
Agricultural lime (calcium carbonate) neutralizes soil acidity by reacting with hydrogen ions to raise pH.
Question 6: What is the main form of nitrogen taken up by most crops from the soil?
- Urea
- Ammonium and nitrate (Correct answer)
- Organic nitrogen
- Dinitrogen gas
Correct answer: Ammonium and nitrate
Most crops absorb nitrogen primarily as ammonium (NH4+) and nitrate (NO3-) ions from the soil solution.
Agronomy Soil Science and Fertility 2
Soil organic matter improves soil structure primarily by doing what?