CCA Soil Management 3

Question 1

Which factor most directly controls the rate of organic matter decomposition in soil?

Accepted Answer

Soil temperature and moisture

Answer

Microbial activity driving decomposition is strongly regulated by temperature and moisture, with optimal rates occurring at warm, moist (but not saturated) conditions.

Question 2

A soil test reveals high phosphorus but low pH. Which condition most likely explains the reduced P availability?

Accepted Answer

P is being fixed by Al and Fe oxides at low pH

Answer

At low pH, aluminum and iron oxides become highly reactive and fix phosphorus into insoluble compounds, reducing plant availability.

Question 3

Which soil texture class has the largest total surface area per unit weight and the highest water-holding capacity?

Accepted Answer

Clay

Answer

Clay particles have the smallest size and therefore the greatest surface area per unit weight, giving clay soils high water-holding and cation exchange capacity.

Question 4

What is the term for the process where fine clay particles move downward through the soil profile and accumulate in a lower horizon?

Accepted Answer

Illuviation

Answer

Illuviation is the process of deposition or accumulation of materials transported from upper horizons into a lower horizon, such as clay forming an argillic horizon.

Question 5

Which cover crop is most effective at scavenging residual soil nitrate and preventing winter leaching losses?

Accepted Answer

Cereal rye

Answer

Cereal rye is a non-legume with extensive fibrous roots that rapidly takes up residual nitrate in fall and winter, preventing leaching losses.

(CCA) Certified Crop Advisor Practice Test

(CCA) Certified Crop Advisor Practice Test

CCA Soil Management 3