Agronomy Basic 3 — Questions and Answers
Question 1: What is the pH range generally considered optimal for most field crops?
- 4.0–5.0
- 5.5–7.0 (Correct answer)
- 7.5–8.5
- 8.5–9.5
Correct answer: 5.5–7.0
Most field crops grow best in slightly acidic to neutral soil with a pH between 5.5 and 7.0, where nutrient availability is highest.
Question 2: Which tillage practice involves turning over the top layer of soil to bury crop residues and expose fresh soil?
- Strip tillage
- Moldboard plowing (Correct answer)
- Chisel plowing
- Ridge tillage
Correct answer: Moldboard plowing
Moldboard plowing inverts the soil, burying surface residues and weeds while bringing subsoil minerals to the surface.
Question 3: What is 'cation exchange capacity' (CEC) a measure of in soil science?
- The soil's ability to hold water
- The soil's ability to retain positively charged nutrient ions (Correct answer)
- The rate of organic matter decomposition
- The depth of the topsoil layer
Correct answer: The soil's ability to retain positively charged nutrient ions
CEC measures the soil's capacity to hold and exchange positively charged ions (cations) such as calcium, magnesium, and potassium.
Question 4: Which of the following best describes 'vernalization' in crop plants?
- The application of green manure to the soil
- Exposure to cold temperatures required to trigger flowering (Correct answer)
- A method of weed control using cover crops
- The process of seed coat scarification
Correct answer: Exposure to cold temperatures required to trigger flowering
Vernalization is the induction of flowering by exposure to prolonged cold, a requirement for many winter cereals like winter wheat.
Question 5: What is the primary role of nitrogen in plant growth?
- Strengthening cell walls
- Building proteins and chlorophyll (Correct answer)
- Regulating water uptake
- Facilitating seed germination
Correct answer: Building proteins and chlorophyll
Nitrogen is a key component of amino acids, proteins, and chlorophyll, making it essential for vegetative growth and photosynthesis.
Question 6: A field with hardpan soil would most likely suffer from which problem?
- Excess nitrogen leaching
- Poor drainage and restricted root growth (Correct answer)
- High cation exchange capacity
- Rapid organic matter buildup
Correct answer: Poor drainage and restricted root growth
Hardpan is a dense, compacted soil layer that restricts water drainage and prevents roots from penetrating deeper soil layers.
Question 7: Which cover crop is most commonly used to add nitrogen back to the soil?
- Winter rye
- Oats
- Hairy vetch (Correct answer)
- Buckwheat
Correct answer: Hairy vetch
Hairy vetch is a legume that fixes atmospheric nitrogen through root nodule bacteria, making it a popular nitrogen-building cover crop.
Agronomy Basic 3
What is the pH range generally considered optimal for most field crops?