CCA Soil Fertility and Analysis 2

Question 1

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?

Accepted Answer

Medium to high

Answer

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 2

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

Accepted Answer

Clay and organic matter

Answer

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

Question 3

Which of the following nitrogen forms is most susceptible to leaching losses in sandy, well-drained soils?

Accepted Answer

Nitrate (NO3-)

Answer

Nitrate carries a negative charge and moves freely with soil water, making it highly susceptible to leaching in coarse-textured soils.

Question 4

A producer applies 200 lb/ac of 0-46-0 (triple superphosphate). How many pounds of P2O5 are applied per acre?

Accepted Answer

92

Answer

The second number in the fertilizer grade represents % P2O5, so 200 lb × 0.46 = 92 lb P2O5/ac.

Question 5

Soil pH of 5.5 is likely to cause reduced availability of which nutrient due to increased fixation by iron and aluminum?

Accepted Answer

Phosphorus

Answer

At pH below 6.0, iron and aluminum ions react with phosphate ions to form insoluble compounds, significantly reducing P availability.

(CCA) Certified Crop Advisor Practice Test

(CCA) Certified Crop Advisor Practice Test

CCA Soil Fertility and Analysis 2