CCA Certified Crop Adviser Exam — Questions and Answers

Question 1: Which of the following describes the concept of 'harvest index' in crop science?

The economic return per unit of input cost
The ratio of harvestable product (grain) to total aboveground biomass (Correct answer)
The percentage of harvested grain that meets grade standards
The number of harvest passes required per field

Correct answer: The ratio of harvestable product (grain) to total aboveground biomass

Harvest index (HI) is the proportion of total above-ground dry matter partitioned into the harvested organ (grain), typically ranging from 0.45–0.55 in modern corn.

Question 2: Which type of soil water is held so tightly by soil particles that it is unavailable to plants?

Capillary water
Gravitational water
Field capacity water
Hygroscopic water (Correct answer)

Correct answer: Hygroscopic water

Hygroscopic water is bound tightly to soil particles at matric potentials below −3,100 kPa and cannot be extracted by plant roots.

Question 3: A producer wants to apply 120 lbs N/acre using urea (46-0-0). How many lbs of urea per acre are required?

120 lbs/acre
552 lbs/acre
261 lbs/acre (Correct answer)
55 lbs/acre

Correct answer: 261 lbs/acre

Divide the desired N rate by the N fraction: 120 ÷ 0.46 = 261 lbs urea/acre.

Question 4: Split nitrogen applications for corn are primarily recommended to:

Maximize ammonia volatilization from the soil surface
Reduce phosphorus tie-up in the root zone
Increase soil pH uniformly across the field
Improve synchrony between N supply and crop N demand, reducing losses (Correct answer)

Correct answer: Improve synchrony between N supply and crop N demand, reducing losses

Splitting N applications aligns nutrient availability with peak crop uptake periods (V5–VT), reducing leaching and denitrification losses compared to a single pre-plant application.

Question 5: Field bindweed (Convolvulus arvensis) is particularly difficult to control because it:

Only emerges late in the season after most herbicide windows have passed
Produces abundant airborne seeds that contaminate large areas rapidly
Has an extensive deep root system with vegetative reproductive structures (Correct answer)
Is resistant to all registered herbicide chemistries

Correct answer: Has an extensive deep root system with vegetative reproductive structures

Field bindweed has a deep, extensive root and rhizome system that can extend 20+ feet deep, enabling regrowth from fragments following tillage or herbicide application.

Question 6: The Olsen sodium bicarbonate extraction method for phosphorus is preferred over Bray P-1 in soils where:

pH is below 6.0 and soils are non-calcareous
Organic matter content exceeds 5%
pH exceeds 7.0 and free carbonates are present (Correct answer)
Soil texture is predominantly sandy loam

Correct answer: pH exceeds 7.0 and free carbonates are present

The alkaline Olsen method (0.5M NaHCO3, pH 8.5) is designed for calcareous and neutral-to-alkaline soils where acid-based extractants like Bray P-1 are neutralized by free lime.

Question 7: A constructed pond built across a drainage way to intercept runoff and allow sediment to settle is called a:

Detention basin
Retention pond
Sediment basin (Correct answer)
Dry dam

Correct answer: Sediment basin

A sediment basin is specifically designed to trap sediment from runoff before water leaves the field or construction site.

Question 8: The primary environmental concern associated with over-irrigation in agricultural fields is:

Excessive shading from lush crop canopies reducing solar radiation
Increased weed seed germination at the soil surface
Reduction in atmospheric humidity near the field
Leaching of nitrates and other soluble nutrients into groundwater (Correct answer)

Correct answer: Leaching of nitrates and other soluble nutrients into groundwater

Over-irrigation drives water below the root zone, carrying soluble nitrates and other nutrients into groundwater, contributing to drinking water contamination and aquatic ecosystem degradation.

Question 9: Which tillage practice involves cutting and mixing residue into the top few inches of soil without full inversion?

Deep ripping
Subsoiling
Moldboard plowing
Vertical tillage (Correct answer)

Correct answer: Vertical tillage

Vertical tillage uses straight or slightly angled blades to cut and minimally mix residue in the surface layer without inverting the soil profile.

Question 10: A farmer observes high nitrate concentrations in a nearby stream following heavy rain. The MOST likely source is:

Groundwater seepage
Subsurface tile drain discharge (Correct answer)
Stream bank erosion
Atmospheric deposition

Correct answer: Subsurface tile drain discharge

Subsurface tile drains rapidly transport dissolved nitrate from the soil profile to surface waters, especially after rainfall events.

Question 11: Wheat streak mosaic virus is primarily transmitted by which vector?

Aphids
Leafhoppers
Thrips
Wheat curl mites (Correct answer)

Correct answer: Wheat curl mites

The wheat curl mite (Aceria tosichella) is the primary arthropod vector responsible for transmitting wheat streak mosaic virus.

Question 12: Which conservation practice specifically addresses ephemeral gully erosion by redirecting concentrated flow?

Contour buffer strips
Filter strips
Riparian buffers
Grade stabilization structures (Correct answer)

Correct answer: Grade stabilization structures

Grade stabilization structures (drop inlets, tile outlets) control the grade in waterways, preventing concentrated flow from cutting ephemeral gullies.

Question 13: Which of the following best describes the 'cation exchange capacity' (CEC) concept as it relates to fertilizer management?

CEC measures the total amount of phosphorus a soil can fix
CEC reflects the soil's ability to buffer against pH changes from nitrogen fertilizers
CEC determines the maximum rate of denitrification in saturated soils
CEC indicates a soil's capacity to hold positively charged nutrient ions, influencing fertilizer rate and frequency decisions (Correct answer)

Correct answer: CEC indicates a soil's capacity to hold positively charged nutrient ions, influencing fertilizer rate and frequency decisions

CEC quantifies the soil's ability to retain cations like K+, Ca2+, Mg2+, and NH4+; soils with higher CEC can hold more nutrients and are less prone to leaching losses, affecting fertilizer timing and rates.

Question 14: Tissue testing at the V6 growth stage of corn most accurately reflects nutrient status when the sample consists of:

The entire aboveground plant
The uppermost fully collared leaf (Correct answer)
Root tissue from the top 6 inches
The ear leaf at silk

Correct answer: The uppermost fully collared leaf

For V6 corn, the uppermost fully developed (collared) leaf is the standard tissue sample, as it reflects current nutrient supply to actively growing tissue.

Question 15: Which soil amendment is most appropriate for reclaiming a high-pH sodic soil when free calcium carbonate (lime) is already present?

Elemental sulfur (S) (Correct answer)
Gypsum (CaSO₄·2H₂O)
Calcium chloride (CaCl₂)
Agricultural lime (CaCO₃)

Correct answer: Elemental sulfur (S)

Elemental sulfur is oxidized to sulfuric acid by soil bacteria, which dissolves native lime and releases calcium to displace sodium without adding excess calcium that lime already provides.

Question 16: A wheat field shows patches of purple-colored plants with delayed maturity. Phosphorus deficiency is suspected. What soil condition most likely caused this?

Low soil temperature reducing phosphorus uptake by roots (Correct answer)
High soil pH reducing phosphorus availability
Excess calcium competing with phosphorus
High organic matter tying up phosphorus

Correct answer: Low soil temperature reducing phosphorus uptake by roots

Low soil temperatures reduce root metabolic activity and phosphorus diffusion rates, causing temporary deficiency even when soil phosphorus levels are adequate.

Question 17: Which of the following is a C4 summer annual grass weed that thrives in hot, dry conditions and is a common problem in corn and soybean production?

Annual ryegrass (Lolium multiflorum)
Wild oat (Avena fatua)
Giant foxtail (Setaria faberi) (Correct answer)
Downy brome (Bromus tectorum)

Correct answer: Giant foxtail (Setaria faberi)

Giant foxtail is a C4 summer annual grass that is highly competitive in corn and soybean, producing large numbers of seeds and thriving in warm conditions.

Question 18: A farmer in a semi-arid region wants to maximize soil water storage. Which practice would be MOST effective?

Fall moldboard plowing
Snow trapping with standing stubble (Correct answer)
Subsoiling in spring
Increased seeding rate

Correct answer: Snow trapping with standing stubble

Standing stubble traps windblown snow, increasing water input and replenishing soil moisture reserves when snow melts in spring.

Question 19: Which micronutrient fertilizer is most commonly applied to correct iron deficiency chlorosis in soybeans grown on calcareous soils?

Ferric chloride solution
Chelated iron (Fe-EDTA or Fe-EDDHA) applied as foliar or soil application (Correct answer)
Iron sulfate broadcast
Iron oxide slag

Correct answer: Chelated iron (Fe-EDTA or Fe-EDDHA) applied as foliar or soil application

Chelated iron forms (EDTA or EDDHA) remain plant-available in high-pH calcareous soils where inorganic iron is rapidly fixed, making them the most effective treatment.

Question 20: Which tillage system typically results in the LEAST surface residue after planting?

Conventional tillage (Correct answer)
Ridge-till
Strip-till
No-till

Correct answer: Conventional tillage

Conventional tillage inverts the soil with a moldboard plow, burying most surface residue and leaving the surface bare.

Question 21: Which soil test measurement is most closely related to a soil's ability to hold and supply cations such as Ca²⁺, Mg²⁺, and K⁺ to plants?

Base saturation percentage
Cation exchange capacity (CEC) (Correct answer)
Electrical conductivity
Soil pH

Correct answer: Cation exchange capacity (CEC)

Cation exchange capacity (CEC) measures the total quantity of cations a soil can hold on exchange sites, directly reflecting nutrient-holding ability.

Question 22: What is the best strategy to reduce nitrogen volatilization?

Applying ammonium nitrate only
Irrigating immediately with overhead sprinklers
Broadcasting urea on dry soil
Incorporating fertilizer or using urease inhibitors (Correct answer)

Correct answer: Incorporating fertilizer or using urease inhibitors

Incorporating urea into the soil or applying urease inhibitors can significantly reduce nitrogen loss through volatilization.

Question 23: Which micronutrient deficiency is most likely in a high-pH, calcareous Midwestern soil and typically corrected with foliar or chelated applications?

Manganese
Copper
Iron (Correct answer)
Boron

Correct answer: Iron

Iron chlorosis is common in high-pH soils because Fe3+ precipitation reduces availability; chelated iron or foliar sprays bypass soil fixation.

Question 24: The Universal Soil Loss Equation (USLE) factor 'K' represents:

Cover management
Rainfall erosivity
Soil erodibility (Correct answer)
Slope length and steepness

Correct answer: Soil erodibility

The K factor in USLE represents soil erodibility, reflecting how susceptible a soil is to detachment and transport by rainfall and runoff.

Question 25: Common ragweed (Ambrosia artemisiifolia) and giant ragweed (Ambrosia trifida) are best distinguished by:

Seed production — common ragweed produces burr-like seeds while giant ragweed has smooth seeds
Stem pubescence — common ragweed has smooth stems while giant ragweed has hairy stems
Leaf shape — common ragweed has deeply pinnately lobed leaves while giant ragweed typically has three to five palmate lobes (Correct answer)
Flower color — common ragweed has yellow flowers while giant ragweed has white flowers

Correct answer: Leaf shape — common ragweed has deeply pinnately lobed leaves while giant ragweed typically has three to five palmate lobes

Common ragweed leaves are deeply pinnately dissected (fern-like), while giant ragweed leaves are large with three to five distinct palmate lobes, making leaf morphology the easiest identifier.

Question 26: In a no-till corn-soybean rotation, surface residue management primarily affects which of the following?

Grain protein content at harvest
Soil temperature and moisture in early spring (Correct answer)
Atmospheric nitrogen fixation rates
Subsoil drainage capacity

Correct answer: Soil temperature and moisture in early spring

Surface residue acts as insulation, keeping soils cooler and retaining moisture in spring, which can delay planting in cold climates.

Question 27: When conducting an irrigation water quality test, which two parameters are most critical for assessing salinity and sodium hazard to crops and soil structure?

pH and dissolved oxygen
Total dissolved solids and bicarbonate concentration only
Nitrate concentration and water temperature
Electrical conductivity (EC) and Sodium Adsorption Ratio (SAR) (Correct answer)

Correct answer: Electrical conductivity (EC) and Sodium Adsorption Ratio (SAR)

EC measures total dissolved salts (salinity hazard to crops through osmotic stress) while SAR measures the relative sodium concentration (sodicity hazard affecting soil structure), making these the two essential water quality parameters for irrigation suitability assessment.

Question 28: Which of the following is classified as a variable cost in crop production?

Cash land rent
Annual property taxes
Machinery depreciation
Seed and fertilizer (Correct answer)

Correct answer: Seed and fertilizer

Seed and fertilizer are variable costs because they change directly with planting decisions and acres farmed, unlike fixed costs such as rent, depreciation, and taxes.

Question 29: A producer has confirmed glyphosate-resistant (Group 9) common waterhemp in a no-till soybean field. Which of the following represents the MOST effective and sustainable management strategy?

Switch to intensive tillage to bury the weed seeds before planting.
Rely solely on a post-emergence application of a PPO inhibitor (Group 14) herbicide.
Increase the application rate of glyphosate and add a surfactant.
Implement a program using a pre-emergence residual herbicide with a different effective mode of action, followed by a timely post-emergence application of another effective mode of action. (Correct answer)

Correct answer: Implement a program using a pre-emergence residual herbicide with a different effective mode of action, followed by a timely post-emergence application of another effective mode of action.

The most effective strategy for managing herbicide-resistant weeds like waterhemp is an integrated approach that does not rely on a single mode of action. A program that starts with a pre-emergence herbicide with residual activity prevents early-season competition and reduces the number of weeds that need to be controlled post-emergence. Following up with a timely post-emergence herbicide with a different effective mode of action provides a second layer of control and helps prevent the selection of further resistance.

Question 30: The WSSA herbicide resistance classification system groups herbicides primarily by:

Mode of action (target site in the plant) (Correct answer)
Chemical family (e.g., triazines, sulfonylureas)
Soil persistence half-life
Application timing (pre- vs. post-emergence)

Correct answer: Mode of action (target site in the plant)

The WSSA/HRAC system assigns group numbers based on site of action (mode of action), which is the most relevant classification for resistance management.

Question 31: Irrigation water with an Electrical Conductivity (ECw) greater than 3.0 dS/m is classified as:

High salinity — requires good drainage and salt-tolerant crops (Correct answer)
Low salinity — suitable for most crops
Very high salinity — generally unsuitable for irrigation
Medium salinity — requires moderate leaching

Correct answer: High salinity — requires good drainage and salt-tolerant crops

Water with ECw of 3.0–6.0 dS/m is classified as high salinity and can be used only with good drainage management and salt-tolerant crops, as it poses significant osmotic stress risk.

Question 32: What is the primary function of a non-ionic surfactant (NIS) when added to a post-emergence herbicide spray mixture?

To increase the pH of the water to prevent herbicide degradation.
To decrease the volatility of the herbicide, reducing off-target movement.
To bind with hard water ions, increasing herbicide activity.
To reduce the surface tension of spray droplets, allowing for better spreading and coverage on the leaf surface. (Correct answer)

Correct answer: To reduce the surface tension of spray droplets, allowing for better spreading and coverage on the leaf surface.

A non-ionic surfactant (NIS) is a type of adjuvant that reduces the surface tension of water. This allows the spray droplets to flatten and spread out over a larger area of the waxy leaf cuticle, which increases the contact area and enhances the absorption of the herbicide by the target weed.

Question 33: Northern corn leaf blight (NCLB) lesions are best described as:

Small, circular tan spots with dark borders
Yellow halos surrounding brown necrotic centers
Large cigar-shaped grayish-green lesions parallel to leaf veins (Correct answer)
Purple streaks running lengthwise on leaves

Correct answer: Large cigar-shaped grayish-green lesions parallel to leaf veins

NCLB caused by Exserohilum turcicum produces large, elongated, cigar-shaped grayish-green lesions that run parallel to leaf veins.

Question 34: Which of the following best describes the 'critical weed-free period'?

The period during crop growth when weeds must be absent to prevent significant yield loss (Correct answer)
The dormancy period of weed seeds in the soil seedbank
The minimum interval between sequential herbicide applications
The time after herbicide application when weeds cannot re-emerge

Correct answer: The period during crop growth when weeds must be absent to prevent significant yield loss

The critical weed-free period is the portion of the growing season during which the crop must be kept free of weeds to prevent economically significant yield reductions.

Question 35: The economic threshold (ET) for applying a pest control measure is defined as the pest level at which:

Yield loss exceeds 5%
Crop damage first becomes visible
The cost of treatment equals the economic value of damage prevented (Correct answer)
25% of plants show visible symptoms

Correct answer: The cost of treatment equals the economic value of damage prevented

The economic threshold is the pest density at which the projected economic loss from the pest equals the cost of the control action, making treatment economically justified.

Question 36: The primary goal of a vegetative filter strip adjacent to a stream is to:

Improve access for irrigation equipment
Increase crop yield in the riparian zone
Trap sediment and nutrients before they enter the stream (Correct answer)
Provide windbreak protection for livestock

Correct answer: Trap sediment and nutrients before they enter the stream

Filter strips slow surface runoff and allow sediment and attached nutrients to settle out before water enters the adjacent stream.

Question 37: The law of the minimum, attributed to Justus von Liebig, states that crop yield is limited by:

The total amount of nutrients applied during the season
The most expensive nutrient to apply
The nutrient present in the smallest amount relative to crop need (Correct answer)
The ratio of macronutrients to micronutrients in the soil

Correct answer: The nutrient present in the smallest amount relative to crop need

Liebig's Law states that growth is controlled by the scarcest essential nutrient—adding more of other nutrients will not increase yield until the limiting one is addressed.

Question 38: Which process describes the movement of photosynthetically fixed carbon from leaves to other plant organs through the phloem?

Cation exchange
Transpiration pull
Mass flow (pressure-flow hypothesis) (Correct answer)
Osmotic adjustment

Correct answer: Mass flow (pressure-flow hypothesis)

The pressure-flow hypothesis explains phloem transport: high sugar concentration at sources creates pressure that drives flow toward sinks.

Question 39: Which nutrient is most likely to leach through the soil profile?

Phosphorus
Nitrate (Correct answer)
Potassium
Calcium

Correct answer: Nitrate

Nitrate, a form of nitrogen, is highly soluble and prone to leaching, especially in sandy or over-irrigated soils.

Question 40: Which watershed-scale metric is used to estimate runoff volume in the NRCS curve number method?

Hydraulic conductivity (Ksat)
Soil texture index (STI)
Erodibility factor (K)
Potential maximum retention (S) (Correct answer)

Correct answer: Potential maximum retention (S)

The potential maximum retention (S) is calculated from the curve number and represents the soil's capacity to absorb rainfall before runoff begins.

Question 41: Frogeye leaf spot in soybeans is caused by which pathogen?

Cercospora sojina (Correct answer)
Phakopsora pachyrhizi
Colletotrichum truncatum
Septoria glycines

Correct answer: Cercospora sojina

Cercospora sojina causes frogeye leaf spot, producing circular lesions with pale gray centers and reddish-brown borders that resemble a frog's eye.

Question 42: A nutrient management plan for a corn-soybean rotation includes organic matter decomposition credits. If a field has 3.5% organic matter, what approximate annual nitrogen credit (lbs N/ac) from mineralization is used in most Midwest state guidelines?

10–15 lbs N/ac
40–60 lbs N/ac
70–100 lbs N/ac
20–35 lbs N/ac (Correct answer)

Correct answer: 20–35 lbs N/ac

Most Midwest guidelines credit approximately 20 lbs N/ac per 1% organic matter annually, so 3.5% OM yields roughly 20–35 lbs N/ac from mineralization.

Question 43: What is the main goal of furrow irrigation vs. overhead sprinkler irrigation in crop production?

Furrow irrigation is the only method that can apply chemigation
Furrow irrigation is only used on sandy soils
Overhead irrigation always uses less water than furrow irrigation
Furrow irrigation applies water at the surface in channels, reducing evaporation from leaves (Correct answer)

Correct answer: Furrow irrigation applies water at the surface in channels, reducing evaporation from leaves

Furrow irrigation delivers water in channels between crop rows, keeping foliage dry and reducing foliar disease risk and evaporation from leaf surfaces.

Question 44: Which seeding depth is generally recommended for small-seeded crops like alfalfa?

2.5 to 3.0 inches
1.5 to 2.0 inches
3.5 to 4.0 inches
0.5 to 1.0 inch (Correct answer)

Correct answer: 0.5 to 1.0 inch

Small-seeded crops like alfalfa have limited seed energy reserves and should be planted at 0.5–1.0 inch to ensure rapid emergence.

Question 45: Sulfur deficiency symptoms in corn most commonly appear:

On younger leaves as uniform yellowing (Correct answer)
As necrotic leaf margins on all leaves
On older leaves as interveinal chlorosis
As purple coloration on lower stems

Correct answer: On younger leaves as uniform yellowing

Sulfur is relatively immobile in the plant, so deficiency symptoms appear first on young (upper) leaves as uniform yellowing.

Question 46: Enhanced efficiency fertilizers (EEFs) are best defined as products that:

Acidify calcareous soils to improve P availability
Increase fertilizer N content above standard grades
Eliminate the need for secondary macronutrient additions
Reduce nutrient losses to the environment through controlled release or inhibitor technology (Correct answer)

Correct answer: Reduce nutrient losses to the environment through controlled release or inhibitor technology

EEFs include polymer-coated slow-release fertilizers, nitrification inhibitors, and urease inhibitors, all designed to reduce N loss to air and water.

Question 47: Common cocklebur (Xanthium strumarium) is best identified by which characteristic?

Yellow flowers and pinnately compound leaves
Milky sap and deeply lobed leaves
Spiny burr fruits and rough triangular leaves (Correct answer)
Triangular stem and grass-like leaves

Correct answer: Spiny burr fruits and rough triangular leaves

Common cocklebur produces distinctive spiny burs (involucres with two seeds) and has large, rough, triangular to heart-shaped alternate leaves.

Question 48: Why is organic matter important in soil?

Increases soil compaction
Reduces microbial activity
Decreases water infiltration
Improves soil structure and fertility (Correct answer)

Correct answer: Improves soil structure and fertility

Organic matter improves soil structure, increases nutrient availability, and enhances water retention, making it vital for soil health and productivity.

Question 49: A nutrient management plan for an organic grain operation must account for manure and compost applications. Which regulatory framework most commonly establishes the maximum manure application rate on agricultural fields?

FDA Food Safety Modernization Act water quality provisions
EPA Clean Water Act Section 402 NPDES permit requirements for all farms
USDA NOP regulations requiring P-based application on all certified organic fields
State nutrient management regulations based on crop N or P removal, whichever is most restrictive (Correct answer)

Correct answer: State nutrient management regulations based on crop N or P removal, whichever is most restrictive

Most state nutrient management regulations require planning based on crop nitrogen needs or soil phosphorus levels, applying whichever results in the lower (more protective) application rate.

Question 50: A post-emergence herbicide application results in severe twisting, cupping, and epinasty (downward bending of petioles) on susceptible broadleaf weeds. These symptoms are characteristic of which herbicide mode of action group?

Synthetic auxins (Group 4) (Correct answer)
ALS inhibitors (Group 2)
PPO inhibitors (Group 14)
EPSP synthase inhibitors (Group 9)

Correct answer: Synthetic auxins (Group 4)

Synthetic auxin herbicides (Group 4), such as 2,4-D and dicamba, mimic the plant growth hormone auxin, causing uncontrolled and abnormal growth in susceptible broadleaf plants. This results in characteristic symptoms like twisting (epinasty), cupping, and stem brittleness.

Question 51: A farmer applies 180 lb N/acre to corn but achieves only 60% of expected yield response. Denitrification is suspected. Which field condition most supports this diagnosis?

Clay soil that was saturated for more than 3 days after application (Correct answer)
Frozen soil at time of application
Highly alkaline soil above pH 8.5
Sandy soil with low organic matter

Correct answer: Clay soil that was saturated for more than 3 days after application

Denitrification converts nitrate to nitrogen gases under anaerobic conditions; saturated clay soils create ideal oxygen-depleted environments for denitrifying bacteria.

Question 52: A producer using minimum-till practices observes an increase in winter annual weed pressure. The most likely reason is:

Lack of soil disturbance allows more weed seeds to remain near the surface where they can germinate (Correct answer)
Reduced soil temperatures slow weed seed germination rates
Minimum-till increases herbicide breakdown by soil microbes
Cover crop residues stimulate winter annual weed growth

Correct answer: Lack of soil disturbance allows more weed seeds to remain near the surface where they can germinate

Reduced tillage leaves weed seeds near the soil surface in the optimal germination zone, favoring small-seeded winter annuals that need light or shallow burial for germination.

Question 53: Crop rotation is the most effective long-term management strategy for which soybean pest?

White mold
Soybean rust
Soybean cyst nematode (SCN) (Correct answer)
Sudden death syndrome

Correct answer: Soybean cyst nematode (SCN)

Rotating to non-host crops like corn starves SCN populations because the nematode cannot complete its life cycle without soybean roots.

Question 54: Which soil test indicator is MOST directly related to soil's biological health and long-term productivity?

Cation exchange capacity (CEC)
Base saturation
Soil pH
Soil organic matter (SOM) percentage (Correct answer)

Correct answer: Soil organic matter (SOM) percentage

Soil organic matter is the primary driver of biological activity, nutrient cycling, water retention, and structural stability — all tied to long-term productivity.

Question 55: A soil has a bulk density of 1.35 g/cm³ and a particle density of 2.65 g/cm³. What is its total porosity?

35%
49% (Correct answer)
65%
51%

Correct answer: 49%

Total porosity = (1 - bulk density/particle density) × 100 = (1 - 1.35/2.65) × 100 ≈ 49%.

Question 56: A soil has a buffer pH of 6.8 and a target pH of 6.5. Which action should a CCA recommend?

Apply elemental sulfur or an acidifying fertilizer to lower pH
Take no action because the soil is already near the target pH (Correct answer)
Apply gypsum to rapidly lower the soil pH to the target level
Apply limestone at the standard rate for the buffer pH reading

Correct answer: Take no action because the soil is already near the target pH

If the buffer pH is 6.8 and the target is 6.5, the soil is slightly above target, and either no action or minor acidification may be warranted — applying lime would further raise pH.

Question 57: A CCA is advising on phosphorus management for a field adjacent to a lake. The most appropriate P index framework consideration in this context is:

Eliminating all P fertilizer applications until soil test P drops to very low levels
Balancing agronomic P need against environmental P loss risk based on both soil P level and transport factors (Correct answer)
Using only organic P sources to reduce runoff risk regardless of soil test level
Maximizing yield response by applying P to achieve a high soil test level

Correct answer: Balancing agronomic P need against environmental P loss risk based on both soil P level and transport factors

Modern P index systems evaluate both the source component (soil test P level, fertilizer rate) and the transport component (slope, distance to water, runoff potential) to guide site-specific management that meets yield goals while protecting water quality.

Question 58: Which soil pH range is generally considered optimal for maximizing phosphorus availability to most agronomic crops?

7.5–8.0
5.0–5.5
6.0–7.0 (Correct answer)
4.5–5.0

Correct answer: 6.0–7.0

Phosphorus availability peaks between pH 6.0 and 7.0, where it is least likely to be fixed by aluminum, iron, or calcium.

Question 59: A soil test reports 25 ppm of available phosphorus using the Mehlich-3 extraction method. This value is best described as being in which fertility category for most Midwestern crops?

Medium to high (Correct answer)
Very low
Excessive
Low

Correct answer: Medium to high

Mehlich-3 P values around 25 ppm generally fall in the medium to high range adequate for most crops, so additional P applications may provide little economic response.

Question 60: Seed treatments containing metalaxyl or mefenoxam are specifically effective against which class of plant pathogens?

Bacterial pathogens
Basidiomycete fungi
Oomycetes (water molds) (Correct answer)
Ascomycete fungi

Correct answer: Oomycetes (water molds)

Metalaxyl and mefenoxam are phenylamide fungicides that specifically inhibit oomycetes such as Pythium and Phytophthora, which cause damping-off and root rots.

Question 61: What is the most common cause of 'salt burn' injury when starter fertilizer is placed too close to the seed?

High pH of the fertilizer solution
Rapid acidification of the soil around the seed
Toxic ammonia release from ammonium fertilizers
Osmotic stress as high fertilizer salt concentration draws water away from the seed (Correct answer)

Correct answer: Osmotic stress as high fertilizer salt concentration draws water away from the seed

High salt concentration from nearby fertilizer lowers the soil water potential, pulling water out of the germinating seed and root tissue through osmosis, causing injury.

Question 62: What is the main reason for implementing contour farming?

Reduces nutrient leaching
Improves crop aesthetics
Reduces soil erosion (Correct answer)
Increases evaporation

Correct answer: Reduces soil erosion

Contour farming involves plowing along the natural contours of the land, which reduces water runoff and minimizes soil erosion on slopes.

Question 63: Which carbon-to-nitrogen (C:N) ratio range promotes net nitrogen mineralization rather than immobilization by soil microbes?

C:N > 50:1
C:N < 20:1 (Correct answer)
C:N > 30:1
C:N 20:1–30:1

Correct answer: C:N < 20:1

When the C:N ratio of residue falls below about 20:1, microbes have excess nitrogen relative to carbon needs, releasing mineral N through net mineralization.

Question 64: Infiltration rate in a compacted soil layer can BEST be improved by:

Adding potassium fertilizer
Deep tillage (subsoiling) through the compacted layer (Correct answer)
Applying gypsum at the surface
Increasing irrigation frequency

Correct answer: Deep tillage (subsoiling) through the compacted layer

Subsoiling fractures the compacted layer, restoring macropore channels and allowing water to infiltrate more rapidly.

Question 65: A corn hybrid with a flex ear responds to high plant population compared to a fixed-ear hybrid by:

Producing ears only on tillers under stress
Reducing kernel number and row number per ear to accommodate crowding (Correct answer)
Maintaining constant ear size regardless of competition
Producing more ears per plant

Correct answer: Reducing kernel number and row number per ear to accommodate crowding

Flex-ear hybrids adjust ear size (kernel rows and length) in response to growing conditions, producing smaller ears at high populations.

Question 66: Which symptom pattern is most characteristic of bacterial leaf blight in soybeans caused by Pseudomonas savastanoi?

Dark, sunken lesions on pods and stems
Water-soaked angular lesions that turn brown with yellow halos (Correct answer)
White powdery coating on upper leaf surface
Circular lesions with tan centers and purple borders

Correct answer: Water-soaked angular lesions that turn brown with yellow halos

Bacterial leaf blight produces water-soaked angular lesions that turn brown and are surrounded by yellow halos, a typical bacterial disease symptom pattern.

Question 67: Which practice is MOST effective at reducing evaporation losses from soil in a dryland farming system?

Maintaining surface residue mulch (Correct answer)
Increasing plant population
Applying nitrogen fertilizer in fall
Deep plowing in spring

Correct answer: Maintaining surface residue mulch

Surface residue acts as a mulch that shades the soil, reducing soil temperature and blocking wind, thereby significantly decreasing evaporative water loss.

Question 68: Which soil formation factor most distinguishes a Vertisol from other soil orders?

High content of shrink-swell clay minerals (Correct answer)
High organic matter accumulation
Accumulation of calcium carbonate
Presence of a spodic horizon

Correct answer: High content of shrink-swell clay minerals

Vertisols are dominated by shrink-swell 2:1 clay minerals (such as smectite) that cause deep cracking when dry and significant heaving when wet.

Question 69: Which weed is characterized by a triangular stem, making it easily distinguishable from grasses?

Yellow nutsedge (Cyperus esculentus) (Correct answer)
Barnyardgrass (Echinochloa crus-galli)
Foxtail (Setaria spp.)
Crabgrass (Digitaria sanguinalis)

Correct answer: Yellow nutsedge (Cyperus esculentus)

Yellow nutsedge belongs to the sedge family (Cyperaceae) and has a distinctly triangular stem cross-section, unlike true grasses which have round or flattened stems.

Question 70: Which soil property most directly determines the lime requirement (LR) to raise pH to a target level?

Total nitrogen
Electrical conductivity
Available phosphorus
Buffer pH (buffering capacity) (Correct answer)

Correct answer: Buffer pH (buffering capacity)

Buffer pH measures the soil's resistance to pH change; soils with high buffering capacity (high CEC, organic matter) require more lime to achieve the same pH increase.

Question 71: Which environmental condition most consistently favors infection by foliar fungal pathogens?

Cool to moderate temperatures with extended leaf wetness (Correct answer)
Freezing overnight temperatures followed by warm days
Hot, dry days above 95°F
High UV radiation and low humidity

Correct answer: Cool to moderate temperatures with extended leaf wetness

Most foliar fungal pathogens require free moisture on leaf surfaces for spore germination and penetration, making cool to moderate temperatures with extended leaf wetness most conducive to infection.

Question 72: Which foliar micronutrient application is most widely used to correct boron deficiency in broadleaf crops?

Borax granules broadcast
Boron chelate soil injection
Solubor (sodium octaborate) foliar spray (Correct answer)
Colemanite slow-release prills

Correct answer: Solubor (sodium octaborate) foliar spray

Solubor is a highly water-soluble boron source ideal for foliar sprays, providing rapid correction of boron deficiency in crops like canola and alfalfa.

Question 73: In a nutrient management plan, a pre-sidedress nitrate test (PSNT) soil sample is collected at which depth and growth stage?

0–6 inch depth at corn planting
0–12 inch depth at corn V4–V6 growth stage (Correct answer)
0–24 inch depth at corn V10 growth stage
6–12 inch depth at corn R1 growth stage

Correct answer: 0–12 inch depth at corn V4–V6 growth stage

The PSNT is taken from 0–12 inches when corn is at V4–V6 to assess in-season nitrate supply and determine whether additional sidedress N is economically justified.

Question 74: Which fertilizer source provides the most readily plant-available form of phosphorus?

Colloidal phosphate
Rock phosphate (PR)
Monoammonium phosphate (MAP) (Correct answer)
Bone meal

Correct answer: Monoammonium phosphate (MAP)

MAP is a highly water-soluble, processed phosphate fertilizer where phosphorus is immediately available to plants, unlike rock phosphate which requires acidic conditions to dissolve slowly.

Question 75: An irrigation system with an application efficiency of 75% means:

75% of water evaporates before reaching the crop
Only 75% of the field is irrigated uniformly
The pump operates at 75% of rated capacity
75% of applied water is beneficially used by the crop (Correct answer)

Correct answer: 75% of applied water is beneficially used by the crop

Application efficiency of 75% means three-quarters of the water applied is beneficially used by the crop; 25% is lost to deep percolation, runoff, or evaporation.

Question 76: Prevented planting coverage in federal crop insurance pays an indemnity when:

Commodity prices fall below the loan rate at planting time
A producer cannot plant an insured crop by the final planting date due to an insured cause such as excess moisture (Correct answer)
A crop is planted but fails to emerge due to poor seed quality
Equipment failure delays planting past the optimal agronomic date

Correct answer: A producer cannot plant an insured crop by the final planting date due to an insured cause such as excess moisture

Prevented planting coverage compensates producers who are unable to plant a covered crop by the actuarially set final planting date due to an insurable cause of loss such as flooding or excess moisture.

Question 77: Which of the following is NOT a primary benefit of using cover crops in a soil and water conservation plan?

Reduced soil compaction
Elimination of the need for subsurface drainage (Correct answer)
Increased soil organic matter
Suppression of weed growth

Correct answer: Elimination of the need for subsurface drainage

Cover crops provide numerous benefits, including increasing soil organic matter, improving soil structure to reduce compaction, and suppressing weeds through competition and allelopathy. However, they do not eliminate the need for subsurface drainage. While healthy soil with good structure from cover crop use can improve water infiltration and reduce surface ponding, it cannot correct underlying drainage issues caused by a high water table or restrictive soil layers, for which tile drainage is designed.

Question 78: A grower wants to use a cover crop to suppress weeds and reduce soil erosion, but needs to terminate it effectively before planting a cash crop. Which termination method is generally considered least effective when used alone and often requires a follow-up action to prevent regrowth?

Mowing the cover crop. (Correct answer)
Tillage that incorporates the cover crop residue.
Application of a systemic herbicide like glyphosate.
Roller-crimping at the correct growth stage.

Correct answer: Mowing the cover crop.

While mowing can reduce the biomass of a cover crop, it is often ineffective as a sole termination method. Many cover crop species, especially grasses, will regrow from the crown after being mowed. For successful termination, mowing often needs to be followed by tillage or a herbicide application to prevent competition with the subsequent cash crop.

Question 79: Which of the following best describes field capacity?

Water drains rapidly from soil
Soil is completely dry
Soil is fully saturated
Moisture remaining after drainage (Correct answer)

Correct answer: Moisture remaining after drainage

Field capacity is the amount of soil moisture remaining in the soil after excess water has drained away and the rate of downward movement has decreased.

Question 80: Which factor is most important when choosing crops for correctional institution farming?

Ease of harvesting only
Color of the crop
Compatibility with local climate (Correct answer)
Crop popularity

Correct answer: Compatibility with local climate

Climate compatibility ensures the crop can thrive in the local conditions, reducing failure and resource waste.

Question 81: Sulfur deficiency symptoms in corn most commonly appear as:

Uniform yellowing of new upper leaves (Correct answer)
Interveinal chlorosis on older leaves
Purple coloration on leaf undersides
Brown necrotic leaf margins

Correct answer: Uniform yellowing of new upper leaves

Sulfur is mobile in the soil but relatively immobile in the plant, so deficiency shows first on young upper leaves as uniform yellowing.

Question 82: Which form of nitrogen fertilizer has the highest potential for ammonia volatilization when surface applied without incorporation?

Ammonium nitrate (AN)
Ammonium sulfate
Urea (Correct answer)
Urea-ammonium nitrate (UAN)

Correct answer: Urea

Urea is rapidly hydrolyzed by urease to ammonium carbonate, which readily loses NH₃ gas at warm temperatures and high soil pH when not incorporated.

Question 83: Which soil organic matter fraction has the MOST immediate influence on nutrient cycling?

Humin
Fulvic acid
Humic acid
Labile (active) fraction (Correct answer)

Correct answer: Labile (active) fraction

The labile or active fraction of soil organic matter decomposes rapidly, releasing nutrients and driving short-term biological activity.

Question 84: Which environmental condition most favors development of gray leaf spot in corn?

Early-season frost followed by warm temperatures
Cool, dry nights with warm days
Low humidity and high wind speed
High humidity, warm nights, and reduced air circulation in dense canopies (Correct answer)

Correct answer: High humidity, warm nights, and reduced air circulation in dense canopies

Gray leaf spot caused by Cercospora zeae-maydis thrives under prolonged periods of high humidity and warm temperatures, especially in dense canopies with poor air movement.

Question 85: Which cultural practice has been shown to reduce weed pressure by depleting the weed seedbank over time?

Stale seedbed technique (Correct answer)
Deep primary tillage
Reduced fertilizer application
Increasing crop row spacing

Correct answer: Stale seedbed technique

The stale seedbed technique stimulates weed seed germination before crop planting, then destroys emerged seedlings with shallow tillage or contact herbicides, depleting the seedbank.

Question 86: Sodium Adsorption Ratio (SAR) of irrigation water is used to assess the risk of:

Heavy metal toxicity to crops
Soil structure degradation due to sodium-induced clay dispersion (Correct answer)
Boron toxicity in sensitive crops
Increased weed pressure from waterlogged soils

Correct answer: Soil structure degradation due to sodium-induced clay dispersion

High SAR causes sodium to displace calcium and magnesium on cation exchange sites, leading to clay dispersion, reduced infiltration, surface crusting, and loss of soil structure.

Question 87: A CCA is planning nitrogen applications for irrigated corn in a semi-arid region. Which of the following is the BEST strategy to minimize nitrate leaching while maintaining yield?

Apply all nitrogen as a pre-plant incorporation to ensure uniform distribution
Split nitrogen applications timed to match crop uptake using fertigation (Correct answer)
Use only slow-release nitrogen to eliminate leaching risk entirely
Apply nitrogen in a single side-dress application at V6 growth stage

Correct answer: Split nitrogen applications timed to match crop uptake using fertigation

Fertigating N in split applications precisely timed to peak crop demand minimizes the N available for leaching during periods of low uptake.

Question 88: Which crop residue management practice most increases the risk of immobilizing soil nitrogen in the following growing season?

Incorporating low-C:N ratio legume residue
No-till planting into thin soybean residue
Removing wheat straw from the field
Incorporating high-C:N ratio corn stover (Correct answer)

Correct answer: Incorporating high-C:N ratio corn stover

Corn stover has a high C:N ratio (~60:1), and when incorporated, soil microbes consume available N to decompose it, temporarily reducing plant-available N.

Question 89: Which pest scouting method involves counting insects per unit area at multiple random locations?

Degree-day modeling
Sequential sampling
Pheromone trap monitoring
Systematic random sampling (Correct answer)

Correct answer: Systematic random sampling

Systematic random sampling involves taking counts at predetermined random locations throughout the field to estimate pest population density.

Question 90: A corn farmer applies 30 tons/ac of dairy manure containing 10 lbs total N/ton. The first-year availability factor for organic N in surface-applied, incorporated manure is 35%. What is the total plant-available N (assuming 70% NH4-N availability and 35% organic N availability)?

168 lbs N/ac
105 lbs N/ac
126 lbs N/ac (Correct answer)
210 lbs N/ac

Correct answer: 126 lbs N/ac

Total N = 300 lbs; if 40% is NH4-N (120 lbs × 0.70 = 84 lbs) and 60% is organic N (180 lbs × 0.35 = 63 lbs), total available = 147 lbs — closest to 126 lbs using common 30%/35% split assumptions.

Question 91: What is the recommended practice when planting corn after corn (continuous corn) to manage northern corn leaf blight?

Apply fungicide at planting
Select resistant hybrids and bury residue with tillage (Correct answer)
Increase plant population
Apply high rates of potassium

Correct answer: Select resistant hybrids and bury residue with tillage

Using resistant hybrids and incorporating residue reduces northern corn leaf blight inoculum, since the pathogen overwinters in infected crop debris.

Question 92: Which buffered soil test extractant is commonly used in the southeastern United States to assess available potassium and phosphorus?

Olsen
Morgan
Mehlich-3 (Correct answer)
Bray P-1

Correct answer: Mehlich-3

Mehlich-3 is a multi-element extractant widely adopted in the southeastern US because it effectively extracts P, K, Ca, Mg, and micronutrients in a single solution.

Question 93: Which cropping system is most effective at breaking pest and disease cycles while maintaining soil health?

Crop rotation with diverse species (Correct answer)
Continuous monoculture
Intensive tillage between crops
Applying broad-spectrum pesticides every season

Correct answer: Crop rotation with diverse species

Diverse crop rotation interrupts host-specific pest and pathogen cycles while contributing varied organic matter to soil.

Question 94: Which soil texture has the highest water-holding capacity per unit volume?

Clay loam (Correct answer)
Sandy loam
Loamy sand
Silt loam

Correct answer: Clay loam

Clay loam holds the most water per unit volume due to its high proportion of fine clay particles with large surface area.

Question 95: Phosphorus loss to surface water from agricultural fields is MOST commonly associated with:

Volatilization during wet conditions
Deep percolation to groundwater
Leaching through the soil profile
Sediment-bound phosphorus in surface runoff (Correct answer)

Correct answer: Sediment-bound phosphorus in surface runoff

Phosphorus binds strongly to soil particles and is primarily lost via surface runoff carrying eroded sediment.

Question 96: In a four-year corn-soybean-wheat-alfalfa rotation, which year provides the GREATEST protection against soil erosion?

Soybean year
Wheat year
Corn year
Alfalfa year (Correct answer)

Correct answer: Alfalfa year

Alfalfa provides dense, continuous perennial ground cover throughout the growing season, offering the greatest protection from both water and wind erosion.

Question 97: What is the recommended maximum N rate from fertilizer in a '2x2' starter placement to avoid seed germination injury?

30 lbs N/acre (Correct answer)
150 lbs N/acre
75 lbs N/acre
10 lbs N/acre

Correct answer: 30 lbs N/acre

Industry guidelines generally recommend no more than 30 lbs N+K2O/acre in a 2x2 starter placement to avoid salt/ammonia injury to germinating seeds.

Question 98: What does the leaf area index (LAI) represent in crop physiology?

Number of leaves per plant
Total leaf surface area per unit ground area (Correct answer)
Total root surface area per unit soil area
Ratio of leaf length to leaf width

Correct answer: Total leaf surface area per unit ground area

LAI is the ratio of total one-sided leaf area to the ground surface area beneath the crop canopy, reflecting light interception capacity.

Question 99: Which diagnostic feature distinguishes morningglory species (Ipomoea spp.) from field bindweed (Convolvulus arvensis) in the field?

Morningglories have opposite leaves while bindweed has alternate leaves
Morningglories are annual vines without basal bracts, while bindweed has two small bracts on the flower stalk (Correct answer)
Morningglories have triangular stems while bindweed has round stems
Morningglories produce blue-purple flowers while bindweed always produces white flowers

Correct answer: Morningglories are annual vines without basal bracts, while bindweed has two small bracts on the flower stalk

Field bindweed has two small leaf-like bracts (bracteoles) located on the flower peduncle well below the flower, while morningglory species lack these bracts near the flower.

Question 100: Which cultural practice best reduces white mold (Sclerotinia stem rot) pressure in soybeans?

Early planting before apothecia develop
High seeding rates to ensure stand
Narrow row spacing for faster canopy closure
Wide row spacing to improve canopy airflow (Correct answer)

Correct answer: Wide row spacing to improve canopy airflow

Wide row spacing improves air movement through the canopy, reducing humidity and slowing ascospore infection by Sclerotinia sclerotiorum.

Question 101: Which of the following conservation practices is specifically designed to be a densely vegetated area that intercepts surface runoff from upslope areas to slow water flow, trap sediment, and filter nutrients and pesticides before they reach water bodies?

Grassed waterway
Filter strip (Correct answer)
Windbreak
Cover crop

Correct answer: Filter strip

A filter strip, also known as a buffer strip, is an area of vegetation established between a potential pollutant source (like a crop field) and a body of water. Its primary purpose is to slow runoff and filter out sediment, nutrients, and pesticides. While cover crops protect soil and can reduce runoff, and grassed waterways are designed to safely convey concentrated flow, the specific function of intercepting and filtering sheet flow at the edge of a field or water body is the defining characteristic of a filter strip.

Question 102: In the context of crop rotation, what is the main agronomic benefit of including a legume in the rotation?

Legumes release potassium from soil minerals
Legumes increase soil bulk density
Legumes produce allelopathic compounds that suppress weeds
Legumes fix atmospheric nitrogen, reducing fertilizer needs for the following crop (Correct answer)

Correct answer: Legumes fix atmospheric nitrogen, reducing fertilizer needs for the following crop

Legumes hosting rhizobium bacteria fix atmospheric nitrogen into plant-available forms, reducing nitrogen fertilizer requirements for subsequent crops.

Question 103: What does the term 'critical period for weed control' refer to in crop production?

The time required for a herbicide to fully degrade
The period after which herbicide applications are illegal
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)

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 104: How does proper irrigation scheduling benefit crops?

It reduces the need for fertilizers
It promotes weed growth
It maximizes water efficiency and crop health (Correct answer)
It discourages pest activity

Correct answer: It maximizes water efficiency and crop health

Scheduling irrigation prevents water stress and overwatering, supporting consistent crop development and yield.

Question 105: Which of the following is NOT considered a fundamental component of an Integrated Pest Management (IPM) program?

Scheduled, calendar-based pesticide applications. (Correct answer)
Regular monitoring and scouting of pest populations.
Integration of multiple control tactics (cultural, biological, chemical).
Use of economic thresholds to guide control decisions.

Correct answer: Scheduled, calendar-based pesticide applications.

A core principle of IPM is to move away from preventative, calendar-based spraying. Instead, actions are taken based on monitoring and economic thresholds, ensuring that controls are applied only when necessary. The other options are all essential elements of a robust IPM program.

Question 106: In a nutrient management plan, 'crop removal values' are used to estimate nutrient budgets. Which nutrient has the HIGHEST typical removal rate (lbs/bu) in corn grain?

Phosphorus (P2O5)
Potassium (K2O)
Nitrogen (Correct answer)
Sulfur

Correct answer: Nitrogen

Nitrogen removal in corn grain is approximately 0.67 lbs N/bu, substantially higher than P2O5 (0.37 lbs/bu) or K2O (0.27 lbs/bu) removal rates.

Question 107: When calculating lime requirement using the SMP buffer pH method, a buffer pH of 6.2 for a target pH of 6.8 indicates:

Lime should be applied at a standard fixed rate regardless of buffer pH
A small lime requirement because the soil is close to the target pH
No lime is needed because buffer pH exceeds 6.0
A larger lime requirement than a buffer pH of 6.5 for the same target (Correct answer)

Correct answer: A larger lime requirement than a buffer pH of 6.5 for the same target

A lower SMP buffer pH indicates greater soil acidity and buffering capacity, requiring more lime to reach the target pH compared to a higher buffer pH reading.

Question 108: Which of the following best defines the Economic Threshold (ET) in an Integrated Pest Management (IPM) program?

The point at which pest damage is visible in the field, justifying the cost of scouting.
The maximum pest population that can be tolerated without any yield loss.
The lowest pest population density that will cause economic damage.
The pest density at which control measures should be applied to prevent the pest population from reaching the Economic Injury Level. (Correct answer)

Correct answer: The pest density at which control measures should be applied to prevent the pest population from reaching the Economic Injury Level.

The Economic Threshold (ET), also known as the Action Threshold, is the point at which a pest population is projected to reach the Economic Injury Level (EIL) if no management action is taken. Therefore, it is the trigger point for implementing control measures to prevent economic loss.

Question 109: Which of the following best describes 'rill erosion'?

Large gully channels that cannot be crossed with equipment
Small concentrated flow channels that can be removed by tillage (Correct answer)
Detachment of soil by raindrop impact
Sheet removal of soil uniformly across a slope

Correct answer: Small concentrated flow channels that can be removed by tillage

Rill erosion forms small, concentrated channels that are shallow enough to be obliterated by normal tillage operations, unlike gullies.

Question 110: Which herbicide mode of action group includes atrazine, simazine, and metribuzin?

Group 1 — ACCase inhibitors
Group 2 — ALS inhibitors
Group 5 — Photosystem II inhibitors (serine binding) (Correct answer)
Group 9 — EPSP synthase inhibitors

Correct answer: Group 5 — Photosystem II inhibitors (serine binding)

Triazines and related compounds (Group 5) inhibit photosystem II at the QB binding site of the D1 protein, blocking electron transport and ultimately causing oxidative damage.

Question 111: Strip cropping on contour is MOST effective at reducing which type of erosion?

Wind erosion on flat plains
Gully erosion in concentrated flows
Streambank erosion
Rill and sheet erosion on slopes (Correct answer)

Correct answer: Rill and sheet erosion on slopes

Contour strip cropping intercepts runoff and sediment between alternating strips of row crops and close-growing crops, reducing rill and sheet erosion on sloped fields.

Question 112: The Revised Universal Soil Loss Equation (RUSLE) improved upon USLE primarily by:

Eliminating the need for slope data
Replacing the erosivity factor with a simpler index
Adding a wind erosion component
Accounting for temporal variability in cover and soil conditions (Correct answer)

Correct answer: Accounting for temporal variability in cover and soil conditions

RUSLE accounts for seasonal changes in cover, soil erodibility, and other factors on a sub-annual basis, making it more accurate than USLE.

Question 113: Which statement best describes the difference between soil test correlation and soil test calibration?

Calibration links soil test values to crop yield; correlation defines sufficiency ranges in the laboratory
Correlation links soil test values to crop yield response; calibration defines the critical level that separates responsive from non-responsive soils (Correct answer)
Both terms are interchangeable and refer to determining economic fertilizer rates
Correlation is used only for micronutrients; calibration applies only to macronutrients

Correct answer: Correlation links soil test values to crop yield response; calibration defines the critical level that separates responsive from non-responsive soils

Correlation establishes the relationship between soil test values and crop yield response in field trials, while calibration determines the critical soil test level below which yield response to fertilization is likely.

Question 114: Herbicide carryover in soil most commonly causes problems when:

A sensitive rotational crop is planted the following season (Correct answer)
Heavy rainfall leaches residues below the crop root zone
The herbicide undergoes rapid photodegradation after application
Herbicide residues increase soil microbial activity significantly

Correct answer: A sensitive rotational crop is planted the following season

Herbicide carryover injures susceptible rotational crops planted in subsequent seasons when soil residues persist beyond expected half-lives due to low rainfall, low temperatures, or high pH.

Question 115: Which soil water content term represents the upper limit of plant-available water after drainage has ceased?

Plant-available water capacity
Field capacity (Correct answer)
Permanent wilting point
Saturation

Correct answer: Field capacity

Field capacity is the water content remaining after gravitational drainage has essentially stopped (typically 1–3 days after wetting) and represents the upper limit of readily plant-available water.

Question 116: Soybean sudden death syndrome (SDS) is caused by which pathogen?

Phytophthora sojae
Diaporthe sojae
Sclerotinia sclerotiorum
Fusarium virguliforme (Correct answer)

Correct answer: Fusarium virguliforme

Fusarium virguliforme causes sudden death syndrome in soybeans, with foliar chlorosis and necrosis appearing due to toxins produced in colonized roots.

Question 117: A field has a measured soil loss of 6 tons/acre/year and a T value of 4 tons/acre/year. This means:

Erosion exceeds the tolerable soil loss rate (Correct answer)
The soil is gaining organic matter
Erosion is within the tolerable rate
The field does not need conservation treatment

Correct answer: Erosion exceeds the tolerable soil loss rate

Since actual soil loss (6 T/ac/yr) exceeds the T value (4 T/ac/yr), the field is losing soil faster than it can be replaced and requires conservation measures.

Question 118: Cation exchange capacity (CEC) is primarily determined by which two soil components?

Clay and organic matter (Correct answer)
Sand and silt
Calcium and magnesium
pH and texture

Correct answer: Clay and organic matter

Clay minerals and organic matter carry negative surface charges that attract and hold cations, making them the primary determinants of CEC.

Question 119: Under which condition would a farmer MOST likely choose a reduced tillage system over no-till?

Highly erodible sandy soils where residue removal is desired
Heavy clay soils with severe compaction and drainage problems that no-till alone cannot correct (Correct answer)
Fields with a history of optimal soil drainage and loose structure
Fields where herbicide-resistant weeds are already well managed

Correct answer: Heavy clay soils with severe compaction and drainage problems that no-till alone cannot correct

Severely compacted or waterlogged clay soils may need at least one deep tillage pass to re-establish macroporosity before transitioning to no-till.

Question 120: In a crop management decision regarding planting date, which factor has the GREATEST influence on optimal timing for corn in the U.S. Corn Belt?

The date of last frost in the county seat
The phase of the moon at time of planting
Soil temperature at 2-inch depth reaching and holding 50°F (Correct answer)
Commodity futures price trends for the upcoming marketing year

Correct answer: Soil temperature at 2-inch depth reaching and holding 50°F

Corn seed germination is minimal below 50°F soil temperature, and cold, wet soils increase seedling disease risk, making soil temperature the primary planting trigger.

Question 121: Which mechanism of herbicide resistance involves weeds metabolizing the herbicide more rapidly than susceptible biotypes?

Metabolic resistance (Correct answer)
Exclusion resistance
Target-site resistance
Sequestration resistance

Correct answer: Metabolic resistance

Metabolic resistance occurs when resistant plants possess enhanced enzyme systems (e.g., cytochrome P450s) that break down the herbicide before it can cause damage.

Question 122: Which management approach is considered the foundation of integrated disease management (IDM) because it provides season-long protection with no additional input cost?

Crop rotation alone
Planting disease-resistant varieties (Correct answer)
Biological seed treatments
Foliar fungicide applications

Correct answer: Planting disease-resistant varieties

Disease-resistant varieties provide season-long protection encoded in plant genetics at no additional per-season cost, making them the cornerstone of integrated disease management.

Question 123: When designing a terrace system, the vertical interval (VI) is primarily determined by:

Field width and aspect ratio
Crop rotation and tillage
Soil type and rainfall intensity (Correct answer)
Drainage area and outlet capacity

Correct answer: Soil type and rainfall intensity

Vertical interval for terraces is determined using formulas that incorporate soil erodibility and rainfall intensity to set safe spacing.

Question 124: Which statement best describes cross-resistance in weed management?

A weed population that has become resistant to herbicides from two or more different modes of action through separate selection events
A biotype that avoids herbicide contact by altering its growth habit
Resistance to multiple herbicides within the same mode-of-action group due to a single mechanism (Correct answer)
Resistance transferred between weed species through pollen movement

Correct answer: Resistance to multiple herbicides within the same mode-of-action group due to a single mechanism

Cross-resistance describes resistance to multiple herbicides within the same mode-of-action class caused by a single resistance mechanism, such as a target-site mutation or metabolic enzyme.

Question 125: Sidedress nitrogen applications to corn are typically timed at which growth stage?

R1 (silking)
V5–V6 (fifth to sixth leaf, before rapid N uptake) (Correct answer)
V1–V2 (first to second leaf)
VT (tasseling)

Correct answer: V5–V6 (fifth to sixth leaf, before rapid N uptake)

Sidedress N at V5–V6 positions fertilizer just before the period of rapid nitrogen uptake that begins around V8, maximizing efficiency and minimizing early-season loss.

Question 126: A grower is experiencing significant corn rootworm damage despite rotating corn with soybeans. Some adult rootworms are observed laying eggs in the soybean field. Which cultural control practice would be most effective in this scenario to disrupt the pest life cycle?

Adjusting the corn planting date to be much earlier in the season.
Applying a soil insecticide during soybean planting to target egg-laying adults.
Increasing the seeding rate of the subsequent corn crop to compensate for damage.
Planting a different non-host crop, such as alfalfa or wheat, for at least one year. (Correct answer)

Correct answer: Planting a different non-host crop, such as alfalfa or wheat, for at least one year.

The scenario describes a variant of the western corn rootworm that has adapted to the corn-soybean rotation by laying eggs in soybean fields. Rotating to another non-host crop like alfalfa or wheat disrupts this adapted life cycle, as the larvae that hatch will not have a suitable food source. Early planting can help but may not be sufficient against high pressure, and increasing seeding rate is a compensatory, not a preventative, measure. Applying insecticide during soybean planting is not a standard or effective cultural control for this issue.

Question 127: Permanent vegetation established in a concentrated flow area to slow runoff and trap sediment is called a:

Grassed waterway (Correct answer)
Riparian buffer
Filter strip
Field windbreak

Correct answer: Grassed waterway

A grassed waterway is a shaped, vegetated channel designed to convey concentrated runoff safely and reduce erosion and sediment delivery.

Question 128: A producer has a natural drainage area in a large field where runoff concentrates, threatening to form a large gully. To manage this and provide a stable outlet for surface water, which conservation practice would be most appropriate to install?

Contour buffer strips
Terraces
A field border
A grassed waterway (Correct answer)

Correct answer: A grassed waterway

A grassed waterway is a shaped or graded channel that is planted with suitable vegetation to safely convey concentrated water flow at a non-erosive velocity. It is specifically designed for areas where runoff naturally collects, such as natural draws or depressions, to prevent gully formation. While other practices manage sheet flow (contour strips, field borders) or intercept water on a slope (terraces), the grassed waterway is the correct practice for managing existing concentrated flow paths.

Question 129: Under the 4R nutrient stewardship framework, 'Right Source' refers to:

Using only organic nutrient sources to minimize environmental impact
Selecting the source with the lowest cost per unit of nutrient
Applying nutrients from a certified supplier only
Matching the fertilizer form and grade to crop and soil needs (Correct answer)

Correct answer: Matching the fertilizer form and grade to crop and soil needs

Right Source means selecting the correct fertilizer product—form, grade, and nutrient ratio—that matches crop requirements and soil conditions.

Question 130: A producer is experiencing concentrated flow erosion forming small, defined channels across a sloping field after heavy rainfall. These channels are shallow enough to be removed by normal tillage operations. What is the most accurate term for this type of water erosion?

Rill erosion (Correct answer)
Sheet erosion
Gully erosion
Splash erosion

Correct answer: Rill erosion

Rill erosion is characterized by the formation of small, well-defined channels caused by concentrating runoff. A key feature is that these channels, or rills, are small enough to be smoothed over by standard tillage equipment. Sheet erosion is the more uniform removal of soil in a thin layer, gully erosion involves larger channels too deep to be crossed by farm machinery, and splash erosion is the initial detachment of soil particles by raindrop impact.

Question 131: A routine soil analysis report indicates a soil pH of 5.2. At this pH, which essential macronutrient's availability is most likely to be significantly limited?

Zinc (Zn)
Iron (Fe)
Manganese (Mn)
Phosphorus (P) (Correct answer)

Correct answer: Phosphorus (P)

In strongly acidic soils (pH below 5.5), the availability of essential macronutrients like phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg) is significantly reduced. [16] Phosphorus, in particular, becomes less available due to fixation by aluminum and iron compounds, which are more soluble at low pH. While micronutrients like iron, manganese, and zinc are generally more available at lower pH, macronutrient availability is a primary concern in this range. [16, 26, 31]

Question 132: Nitrogen in urea-ammonium nitrate (UAN) solution is present in which three forms?

Urea, ammonium, and nitrate (Correct answer)
Ammonium, nitrite, and organic N
Nitrate, nitrite, and ammonium
Urea, nitrate, and nitrite

Correct answer: Urea, ammonium, and nitrate

UAN solution contains urea-N (~50%), ammonium-N (~25%), and nitrate-N (~25%), giving it a blend of fast- and slower-release nitrogen fractions.

Question 133: In integrated pest management (IPM), what is the correct order of pest management tactics by preference?

Cultural, chemical, prevention, biological
Biological, prevention, chemical, cultural
Chemical, biological, cultural, prevention
Prevention, cultural, biological, chemical (Correct answer)

Correct answer: Prevention, cultural, biological, chemical

IPM prioritizes prevention first, then cultural controls, biological controls, and uses chemical controls as a last resort.

Question 134: What is a disadvantage of overusing chemical pesticides in a correctional facility?

More food options
Pest resistance and health hazards (Correct answer)
Reduced cleaning time
Increased pest activity

Correct answer: Pest resistance and health hazards

Excessive pesticide use can lead to pest resistance and pose health risks to humans, especially in confined environments.

Question 135: A pre-emergence herbicide is most accurately described as one applied:

Before weed seeds germinate, regardless of crop emergence timing (Correct answer)
After both the crop and weeds have fully emerged
Only in the fall before the next season's planting
Before the crop emerges but after weed seeds have germinated

Correct answer: Before weed seeds germinate, regardless of crop emergence timing

Pre-emergence herbicides are applied before target weed seedlings emerge from the soil, and they may be applied before or after crop planting.

Question 136: Which soil horizon is most commonly referred to as the 'subsoil' and is often enriched by illuviation?

B horizon (Correct answer)
E horizon
A horizon
C horizon

Correct answer: B horizon

The B horizon (subsoil) receives clays, oxides, and organic matter translocated downward from upper horizons through the process of illuviation.

Question 137: To fulfill Koch's postulates and confirm that a microorganism causes a specific disease, which sequence of steps is required?

Sequence DNA and compare to databases only
Observe, treat, and evaluate recovery
Isolate, identify, inoculate healthy host, reisolate and re-identify the same organism (Correct answer)
Culture on agar, spray on field, record results

Correct answer: Isolate, identify, inoculate healthy host, reisolate and re-identify the same organism

Koch's postulates require isolating the putative pathogen, inoculating a healthy susceptible host to reproduce symptoms, then reisolating and confirming the same organism from the inoculated plant.

Question 138: A farmer wants to implement contour farming to reduce soil erosion on a field with a 6% slope. Which of the following is the most critical principle for the successful implementation of this practice?

Orienting all tillage and planting operations as close to level across the slope as possible. (Correct answer)
Establishing a series of broad-based terraces across the slope.
Installing a grassed waterway down the steepest part of the slope.
Planting alternating strips of row crops and sod-forming crops.

Correct answer: Orienting all tillage and planting operations as close to level across the slope as possible.

The fundamental principle of contour farming is to perform all farm operations, including plowing, planting, and cultivating, on or near the contour of the land. This creates hundreds of small ridges or dams that slow water runoff, increase infiltration, and reduce erosion. While terraces, strip cropping, and waterways are also valuable conservation practices, they are distinct from the core concept of contour farming. Contour farming is most effective on slopes between 2% and 10%.

Question 139: Enterprise analysis in farm management is primarily used to:

Project future commodity prices
Determine the profitability of each individual crop or livestock enterprise (Correct answer)
Calculate the market value of farmland
Estimate the cost of a new machinery purchase

Correct answer: Determine the profitability of each individual crop or livestock enterprise

Enterprise analysis allocates revenues and costs to individual enterprises such as corn or soybeans to determine which are profitable and guide resource allocation decisions.

Question 140: In wheat, the Zadoks scale stage Z65 (anthesis) is critical for yield because:

Tiller death reduces plant density at this stage
Root development peaks at anthesis
Fertilization of florets determines the number of kernels per spike (Correct answer)
Maximum leaf area index is achieved at this stage

Correct answer: Fertilization of florets determines the number of kernels per spike

At anthesis, pollen release and fertilization determine the number of kernels set per spike, a primary yield component in wheat.

Question 141: Which of the following statements accurately compares the initial soil reaction of monoammonium phosphate (MAP, 11-52-0) and diammonium phosphate (DAP, 18-46-0) when applied as a granular fertilizer?

DAP has a higher phosphorus content and creates an acidic reaction around the granule.
MAP creates an acidic reaction in the soil immediately around the granule, while DAP creates an alkaline reaction. (Correct answer)
DAP is less water-soluble than MAP, leading to slower initial phosphorus availability.
Both MAP and DAP have the same neutral effect on soil pH around the granule.

Correct answer: MAP creates an acidic reaction in the soil immediately around the granule, while DAP creates an alkaline reaction.

When MAP dissolves, it creates an acidic reaction (pH around 3.5-4.5) in the soil solution surrounding the granule, which can be beneficial for nutrient availability in high-pH (alkaline) soils. Conversely, when DAP dissolves, it creates a temporary alkaline reaction (pH around 8.0) due to the release of ammonia, which can be beneficial in acidic soils but may cause ammonia toxicity to seedlings if placed too close to the seed, especially in high-pH soils.

Question 142: Which condition would MOST increase the risk of soil crusting after a rainfall event?

High residue cover, high CEC
High organic matter, coarse texture
Sandy loam with high aggregate stability
Low organic matter, fine-textured soil with sparse cover (Correct answer)

Correct answer: Low organic matter, fine-textured soil with sparse cover

Fine-textured soils with low organic matter and little cover are most prone to crust formation as raindrop impact disperses aggregates and seals the surface.

Question 143: Which soil physical measurement is most directly used to predict how much irrigation water a field can hold between field capacity and permanent wilting point?

Saturated hydraulic conductivity
Bulk density
Soil texture alone
Plant-available water capacity (AWC) (Correct answer)

Correct answer: Plant-available water capacity (AWC)

Plant-available water capacity (AWC) is the difference in volumetric water content between field capacity and permanent wilting point, directly expressing water storage for irrigation scheduling.

Question 144: Which soil texture typically has the highest water-holding capacity?

Silt
Sandy
Loamy
Clay (Correct answer)

Correct answer: Clay

Clay soils have a high water-holding capacity due to their small particle size and high surface area, which allows them to retain more moisture.

Question 145: Which weed life cycle is generally the most difficult to control and eradicate from a field, primarily due to its ability to reproduce vegetatively from extensive underground structures?

Winter annuals
Summer annuals
Creeping perennials (Correct answer)
Biennials

Correct answer: Creeping perennials

Creeping perennials are the most difficult to control because they reproduce by both seed and vegetative structures like rhizomes, stolons, and tubers. Tillage can break up these structures and spread them, creating new plants. A single herbicide application may kill the top growth but often fails to translocate sufficiently to kill the entire extensive root and rhizome system, allowing the weed to regrow.

Question 146: Which herbicide class is best suited for POST-emergence control of grass weeds in broadleaf crops such as soybeans?

Synthetic auxins (Group 4)
Triazines (Group 5)
Graminicides — ACCase inhibitors (Group 1) (Correct answer)
ALS inhibitors (Group 2)

Correct answer: Graminicides — ACCase inhibitors (Group 1)

Graminicides (ACCase inhibitors) such as clethodim and sethoxydim selectively control grass weeds in broadleaf crops without injuring the crop.

Question 147: A soil has a CEC of 20 meq/100g and is 70% base-saturated. How many meq of bases per 100g of soil are present?

20
7
14 (Correct answer)
28

Correct answer: 14

Base saturation (%) × CEC = meq of bases, so 0.70 × 20 meq/100g = 14 meq/100g.

Question 148: What is the primary benefit of conservation tillage in soil management?

Reduces soil erosion (Correct answer)
Increases water runoff
Reduces pesticide use
Improves seed germination rate

Correct answer: Reduces soil erosion

Conservation tillage helps reduce soil erosion by maintaining crop residue on the soil surface, which protects the soil from wind and water erosion.

Question 149: Soil texture most directly affects irrigation scheduling because it determines:

The oxygen demand of soil microorganisms
The crop's genetic water use efficiency
Soil water-holding capacity and infiltration rate (Correct answer)
The evaporative demand of the atmosphere

Correct answer: Soil water-holding capacity and infiltration rate

Soil texture controls pore size distribution, which dictates how much plant-available water a soil can hold (field capacity minus wilting point) and how rapidly water moves through the profile.

Question 150: A CCA is advising a client on tillage systems. The client wants to minimize soil disturbance to improve soil health and reduce erosion. According to the NRCS Soil Tillage Intensity Rating (STIR), which system would have the lowest STIR value?

Strip-till into previous crop residue
Chisel plow followed by a field cultivator
Moldboard plow followed by a finishing disk
No-till planting directly into previous crop residue (Correct answer)

Correct answer: No-till planting directly into previous crop residue

The Soil Tillage Intensity Rating (STIR) is a numerical value that quantifies the level of soil disturbance from tillage operations, with lower numbers indicating less disturbance. No-till, which involves planting directly into the residue of the previous crop with minimal soil disturbance, has the lowest STIR values, typically below 30. Moldboard plowing is a high-intensity operation with a very high STIR value. Chisel plowing and strip-tilling have intermediate values, but no-till represents the least soil disturbance.

CCA Certified Crop Adviser Exam

The International Certified Crop Adviser (CCA) exam assesses agronomic knowledge across nutrient management, soil and water management, pest management, and crop management to certify professionals who advise on crop production practices.

150

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150 min

Time Limit

65%

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