American Society of Agronomy CCA International Exam (pdf) |
2026/2027 | Certification Q&A | Agronomy
1. According to the CCA Performance Objectives, which of the following
correctly describes the relationship between cation exchange capacity (CEC)
and nutrient retention in soil?
A) Soils with low CEC retain nutrients more effectively than soils with high
CEC
B) CEC is a measure of a soil's ability to hold negatively charged nutrient ions
and influences their leaching potential
C) CEC is primarily determined by soil pH and is unrelated to nutrient
availability
D) CEC only affects the retention of micronutrients, not macronutrients
Correct Answer: CEC is a measure of a soil's ability to hold negatively
charged nutrient ions and influences their leaching potential
Rationale: Cation exchange capacity is a fundamental soil property that
measures the soil's ability to hold positively charged nutrient ions (cations)
on negatively charged exchange sites. Soils with higher CEC retain cations
like potassium, calcium, and magnesium more effectively, reducing leaching
losses. Understanding CEC is essential for making nutrient management
recommendations.
2. A grower applies anhydrous ammonia to a field in the fall. Based on the
nitrogen cycle, which of the following is the most likely pathway for nitrogen
loss from the soil before spring planting?
A) Denitrification only
B) Volatilization only
C) Leaching of nitrate following nitrification
D) Immobilization into soil organic matter
,Correct Answer: Leaching of nitrate following nitrification
Rationale: Anhydrous ammonia applied in the fall undergoes nitrification
(conversion of ammonium to nitrate) as soil temperatures remain above
freezing. Nitrate is highly mobile in soil and is susceptible to leaching with
winter precipitation, particularly in coarse-textured soils or poorly drained
areas. This is a primary concern for fall-applied nitrogen in humid regions.
3. A soil test report recommends applying 200 lbs of actual nitrogen per acre
for corn. The grower plans to use urea (46-0-0) as the nitrogen source. How
many pounds of urea are needed to supply the recommended nitrogen?
A) 200 lbs urea
B) 350 lbs urea
C) 435 lbs urea
D) 500 lbs urea
Correct Answer: 435 lbs urea
Rationale: Urea is 46% nitrogen by weight. To calculate the amount of urea
needed, divide the desired nitrogen rate (200 lbs N) by the percentage of
nitrogen in the fertilizer (0.46). .46 = 434.8 lbs, rounded to 435 lbs of
urea. This calculation is a fundamental skill for fertilizer recommendation and
application.
4. Which of the following is the most accurate method for determining the
nitrogen fertilizer requirement for a corn crop?
A) Applying a standard nitrogen rate based on the previous crop
B) Using a pre-sidedress nitrate test (PSNT) or late spring nitrate test
C) Applying nitrogen based solely on the grower's past experience
D) Using the yield goal method without soil or tissue testing
,Correct Answer: Using a pre-sidedress nitrate test (PSNT) or late spring
nitrate test
Rationale: The PSNT measures soil nitrate levels in the upper foot of soil just
before rapid crop nitrogen uptake begins. This test helps account for nitrogen
mineralization from organic matter, manure, and previous legume crops,
allowing for more precise nitrogen rate adjustments and reducing
environmental losses. It is a widely recommended practice for optimizing
nitrogen management.
5. A soil test indicates a pH of 5.2 for a field intended for alfalfa production.
What is the most appropriate recommendation for this field?
A) No lime is needed
B) Apply sulfur to lower the pH further
C) Apply lime to raise the pH to the target range of 6.5-7.0
D) Apply gypsum to correct the pH
Correct Answer: Apply lime to raise the pH to the target range of 6.5-7.0
Rationale: Alfalfa is highly sensitive to soil acidity and performs best at a pH
between 6.5 and 7.0. A pH of 5.2 is strongly acidic and would significantly
reduce alfalfa yield and persistence. Lime application is the standard practice
to raise soil pH, and the amount required should be determined by the buffer
pH or SMP buffer test.
6. According to the CCA Pest Management competency, what is the
economic threshold for a pest?
A) The pest population level at which all pests are eliminated
B) The pest population level at which control measures should be initiated to
prevent economic loss
, C) The pest population level that causes complete crop failure
D) The pest population level at which pesticides are no longer effective
Correct Answer: The pest population level at which control measures should
be initiated to prevent economic loss
Rationale: The economic threshold is the pest density at which the cost of
pest damage equals the cost of control measures. When pest populations
reach this threshold, action should be taken to prevent economic injury. This
concept is central to integrated pest management (IPM) decision-making.
7. A field is being scouted for soybean aphids. The CCA observes an average
of 300 aphids per plant on 80% of the plants, and populations are increasing.
Which of the following is the most appropriate management action?
A) No action is needed because the population is below the economic
threshold
B) Apply a foliar insecticide to prevent yield loss
C) Increase the seeding rate for the next season
D) Apply a fungicide to control aphid-vectored diseases
Correct Answer: Apply a foliar insecticide to prevent yield loss
Rationale: The economic threshold for soybean aphids is approximately 250
aphids per plant with increasing populations. At 300 aphids per plant on 80%
of plants, the population has exceeded the threshold and is expected to
cause yield loss. A foliar insecticide application is the recommended control
measure.
8. Which of the following tillage systems is most effective at reducing soil
erosion on sloping land while maintaining adequate crop productivity?
A) Moldboard plow with fall chisel plow
2026/2027 | Certification Q&A | Agronomy
1. According to the CCA Performance Objectives, which of the following
correctly describes the relationship between cation exchange capacity (CEC)
and nutrient retention in soil?
A) Soils with low CEC retain nutrients more effectively than soils with high
CEC
B) CEC is a measure of a soil's ability to hold negatively charged nutrient ions
and influences their leaching potential
C) CEC is primarily determined by soil pH and is unrelated to nutrient
availability
D) CEC only affects the retention of micronutrients, not macronutrients
Correct Answer: CEC is a measure of a soil's ability to hold negatively
charged nutrient ions and influences their leaching potential
Rationale: Cation exchange capacity is a fundamental soil property that
measures the soil's ability to hold positively charged nutrient ions (cations)
on negatively charged exchange sites. Soils with higher CEC retain cations
like potassium, calcium, and magnesium more effectively, reducing leaching
losses. Understanding CEC is essential for making nutrient management
recommendations.
2. A grower applies anhydrous ammonia to a field in the fall. Based on the
nitrogen cycle, which of the following is the most likely pathway for nitrogen
loss from the soil before spring planting?
A) Denitrification only
B) Volatilization only
C) Leaching of nitrate following nitrification
D) Immobilization into soil organic matter
,Correct Answer: Leaching of nitrate following nitrification
Rationale: Anhydrous ammonia applied in the fall undergoes nitrification
(conversion of ammonium to nitrate) as soil temperatures remain above
freezing. Nitrate is highly mobile in soil and is susceptible to leaching with
winter precipitation, particularly in coarse-textured soils or poorly drained
areas. This is a primary concern for fall-applied nitrogen in humid regions.
3. A soil test report recommends applying 200 lbs of actual nitrogen per acre
for corn. The grower plans to use urea (46-0-0) as the nitrogen source. How
many pounds of urea are needed to supply the recommended nitrogen?
A) 200 lbs urea
B) 350 lbs urea
C) 435 lbs urea
D) 500 lbs urea
Correct Answer: 435 lbs urea
Rationale: Urea is 46% nitrogen by weight. To calculate the amount of urea
needed, divide the desired nitrogen rate (200 lbs N) by the percentage of
nitrogen in the fertilizer (0.46). .46 = 434.8 lbs, rounded to 435 lbs of
urea. This calculation is a fundamental skill for fertilizer recommendation and
application.
4. Which of the following is the most accurate method for determining the
nitrogen fertilizer requirement for a corn crop?
A) Applying a standard nitrogen rate based on the previous crop
B) Using a pre-sidedress nitrate test (PSNT) or late spring nitrate test
C) Applying nitrogen based solely on the grower's past experience
D) Using the yield goal method without soil or tissue testing
,Correct Answer: Using a pre-sidedress nitrate test (PSNT) or late spring
nitrate test
Rationale: The PSNT measures soil nitrate levels in the upper foot of soil just
before rapid crop nitrogen uptake begins. This test helps account for nitrogen
mineralization from organic matter, manure, and previous legume crops,
allowing for more precise nitrogen rate adjustments and reducing
environmental losses. It is a widely recommended practice for optimizing
nitrogen management.
5. A soil test indicates a pH of 5.2 for a field intended for alfalfa production.
What is the most appropriate recommendation for this field?
A) No lime is needed
B) Apply sulfur to lower the pH further
C) Apply lime to raise the pH to the target range of 6.5-7.0
D) Apply gypsum to correct the pH
Correct Answer: Apply lime to raise the pH to the target range of 6.5-7.0
Rationale: Alfalfa is highly sensitive to soil acidity and performs best at a pH
between 6.5 and 7.0. A pH of 5.2 is strongly acidic and would significantly
reduce alfalfa yield and persistence. Lime application is the standard practice
to raise soil pH, and the amount required should be determined by the buffer
pH or SMP buffer test.
6. According to the CCA Pest Management competency, what is the
economic threshold for a pest?
A) The pest population level at which all pests are eliminated
B) The pest population level at which control measures should be initiated to
prevent economic loss
, C) The pest population level that causes complete crop failure
D) The pest population level at which pesticides are no longer effective
Correct Answer: The pest population level at which control measures should
be initiated to prevent economic loss
Rationale: The economic threshold is the pest density at which the cost of
pest damage equals the cost of control measures. When pest populations
reach this threshold, action should be taken to prevent economic injury. This
concept is central to integrated pest management (IPM) decision-making.
7. A field is being scouted for soybean aphids. The CCA observes an average
of 300 aphids per plant on 80% of the plants, and populations are increasing.
Which of the following is the most appropriate management action?
A) No action is needed because the population is below the economic
threshold
B) Apply a foliar insecticide to prevent yield loss
C) Increase the seeding rate for the next season
D) Apply a fungicide to control aphid-vectored diseases
Correct Answer: Apply a foliar insecticide to prevent yield loss
Rationale: The economic threshold for soybean aphids is approximately 250
aphids per plant with increasing populations. At 300 aphids per plant on 80%
of plants, the population has exceeded the threshold and is expected to
cause yield loss. A foliar insecticide application is the recommended control
measure.
8. Which of the following tillage systems is most effective at reducing soil
erosion on sloping land while maintaining adequate crop productivity?
A) Moldboard plow with fall chisel plow
