CCA Crop Management 2 — Questions and Answers
Question 1: Which tillage practice leaves at least 30% crop residue on the soil surface after planting?
- Conventional tillage
- Conservation tillage (Correct answer)
- Deep tillage
- Inversion tillage
Correct answer: Conservation tillage
Conservation tillage is defined by leaving 30% or more crop residue on the surface to reduce erosion and improve soil health.
Question 2: A corn field shows interveinal chlorosis on older leaves first. Which nutrient deficiency is most likely?
- Iron
- Manganese
- Magnesium (Correct answer)
- Zinc
Correct answer: Magnesium
Magnesium is mobile in the plant, so deficiency symptoms appear on older (lower) leaves first as an interveinal chlorosis.
Question 3: What is the primary purpose of a cover crop termination window before cash crop planting?
- Maximize cover crop seed production
- Allow residue decomposition and reduce allelopathy risk (Correct answer)
- Increase soil compaction for better seed contact
- Eliminate beneficial insects before planting
Correct answer: Allow residue decomposition and reduce allelopathy risk
Terminating cover crops 2–4 weeks before planting allows residue to begin decomposing and reduces allelopathic compounds that can inhibit cash crop germination.
Question 4: Which growth stage is the most critical period for water stress in corn yield determination?
- V6 (6-leaf)
- VT/R1 (tasseling/silking) (Correct answer)
- R3 (milk)
- R5 (dent)
Correct answer: VT/R1 (tasseling/silking)
Water stress during VT/R1 (tasseling and silking) causes the greatest yield loss because pollination and kernel set are directly impaired.
Question 5: A farmer wants to reduce soybean cyst nematode (SCN) populations. Which practice is most effective long-term?
- Apply nematicide every year
- Plant SCN-resistant varieties in rotation with non-host crops (Correct answer)
- Increase seeding rate by 20%
- Apply potassium fertilizer at high rates
Correct answer: Plant SCN-resistant varieties in rotation with non-host crops
Rotating SCN-resistant varieties with non-host crops (e.g., corn) is the most sustainable and cost-effective long-term management strategy.
Question 6: What does the term 'critical period for weed control' refer to in crop production?
- The time weeds must be controlled to prevent seed bank buildup
- The crop growth window during which weed competition causes unacceptable yield loss (Correct answer)
- The period after which herbicide applications are illegal
- The time required for a herbicide to fully degrade
Correct answer: The crop growth window during which weed competition causes unacceptable yield loss
The critical period for weed control is the specific crop growth window during which weeds must be removed to prevent economically significant yield loss.
Question 7: Which factor most directly determines the economic threshold for pest management decisions?
- Pest population density relative to crop value and control cost (Correct answer)
- Number of years the pest has been present in the field
- Soil organic matter content
- Distance to the nearest water body
Correct answer: Pest population density relative to crop value and control cost
The economic threshold is the pest density at which the cost of control equals the economic damage prevented, balancing crop value against control costs.
CCA Crop Management 2
Which tillage practice leaves at least 30% crop residue on the soil surface after planting?