CCA Soil Fertility and Analysis 3

Question 1

A corn crop yielding 200 bu/ac removes approximately how many pounds of nitrogen per acre in the harvested grain?

Accepted Answer

150–170 lb

Answer

Corn grain contains roughly 0.75–0.85 lb N per bushel, so 200 bu/ac removes approximately 150–170 lb N/ac in grain alone.

Question 2

Sulfur deficiency symptoms in corn most commonly appear:

Accepted Answer

On younger leaves as uniform yellowing

Answer

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

Question 3

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

Accepted Answer

Buffer pH (buffering capacity)

Answer

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 4

Denitrification occurs most rapidly under which soil conditions?

Accepted Answer

Wet, anaerobic, warm temperature

Answer

Denitrifying bacteria convert NO3- to N2 gases under anaerobic (waterlogged) conditions, and the process accelerates as soil temperature rises.

Question 5

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?

Accepted Answer

14

Answer

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

(CCA) Certified Crop Advisor Practice Test

(CCA) Certified Crop Advisor Practice Test

CCA Soil Fertility and Analysis 3