Agronomy Agronomy MCQ 5 — Questions and Answers
Question 1: What is the main purpose of applying a pre-emergent herbicide?
- Kill established weeds before crop planting
- Prevent weed seed germination after planting but before emergence (Correct answer)
- Control insect pests in the soil
- Stimulate early crop germination
Correct answer: Prevent weed seed germination after planting but before emergence
Pre-emergent herbicides form a chemical barrier in the soil that inhibits weed seed germination and early seedling growth before weeds emerge.
Question 2: In corn production, what is the 'critical period for weed control'?
- 2–4 weeks after planting when soil is warming
- V1 to V8 growth stages when weeds compete most for resources (Correct answer)
- After tasseling when grain fill begins
- At planting when seed germination occurs
Correct answer: V1 to V8 growth stages when weeds compete most for resources
Weeds emerging with corn during the V1–V8 period cause the greatest yield loss because they compete directly for light, water, and nutrients during early crop establishment.
Question 3: Which type of fertilizer application places nutrients directly in the root zone near the seed at planting?
- Broadcast application
- Topdressing
- Starter fertilizer (in-furrow or 2×2) (Correct answer)
- Foliar application
Correct answer: Starter fertilizer (in-furrow or 2×2)
Starter fertilizer placed in-furrow or 2 inches beside and 2 inches below the seed supplies readily available nutrients to seedling roots in cool, wet conditions.
Question 4: What does the term 'lodging' refer to in cereal crops?
- Storage of grain in silos after harvest
- Premature stem breakage or root failure causing plants to fall over (Correct answer)
- Formation of grain in the head
- Accumulation of water in field depressions
Correct answer: Premature stem breakage or root failure causing plants to fall over
Lodging occurs when cereal crop stems break (stem lodging) or roots give way (root lodging), reducing harvestability and grain yield.
Question 5: Which method is used to determine the lime requirement of an acidic soil?
- Electrical conductivity measurement
- Buffer pH test (e.g., Shoemaker-McLean-Pratt) (Correct answer)
- Nitrate leaching test
- Soil respiration assay
Correct answer: Buffer pH test (e.g., Shoemaker-McLean-Pratt)
A buffer pH test measures soil's resistance to pH change and is used to calculate how much agricultural lime is needed to raise pH to a target level.
Question 6: Which pest is the primary vector for Barley Yellow Dwarf Virus (BYDV) in small grains?
- Hessian fly
- Wheat stem sawfly
- Aphids (Correct answer)
- Armyworm
Correct answer: Aphids
Aphids, particularly the bird cherry-oat aphid and English grain aphid, transmit BYDV to wheat, barley, and oats during feeding.
Question 7: The concept of 'evapotranspiration' (ET) in agronomy combines which two processes?
- Photosynthesis and respiration
- Soil evaporation and plant transpiration (Correct answer)
- Infiltration and runoff
- Nutrient uptake and leaching
Correct answer: Soil evaporation and plant transpiration
Evapotranspiration is the combined water loss from soil surface evaporation and plant leaf transpiration, used to schedule irrigation.
Agronomy Agronomy MCQ 5
What is the main purpose of applying a pre-emergent herbicide?