CFA Soil Science & Fertilizer Chemistry 2

Question 1

Which soil textural class has the highest water-holding capacity per unit volume?

Accepted Answer

Clay

Answer

Clay soils have the greatest surface area per gram, giving them the highest water-holding capacity.

Question 2

The process by which ammonium ions are converted to nitrate in the soil is called:

Accepted Answer

Nitrification

Answer

Nitrification is the two-step microbial oxidation of NH4+ to NO2- and then to NO3- by Nitrosomonas and Nitrobacter bacteria.

Question 3

Which fertilizer material has the highest potential acidity when applied to soil?

Accepted Answer

Ammonium sulfate

Answer

Ammonium sulfate has the highest potential acidity (110 lb CaCO3 equivalent per 100 lb) because it supplies two acid-forming NH4+ ions plus the acidifying sulfate anion.

Question 4

What is the primary function of molybdenum (Mo) in plant nutrition?

Accepted Answer

Nitrate reductase activation

Answer

Molybdenum is a cofactor for nitrate reductase, the enzyme that reduces NO3- to NH4+ within plant tissue.

Question 5

A soil with a CEC of 20 meq/100g and 60% base saturation contains how many meq of base cations per 100g?

Accepted Answer

12 meq

Answer

Base saturation percentage × CEC = 0.60 × 20 meq/100g = 12 meq/100g of base cations.

CFA Practice Test

CFA Practice Test

CFA Soil Science & Fertilizer Chemistry 2