CFA Soil Properties and Testing Questions and Answers

Question 1

A soil test report for a sandy loam field indicates a low Cation Exchange Capacity (CEC). Which of the following fertilizer application strategies is most appropriate for this field?

Accepted Answer

Split applications of fertilizer in smaller, more frequent doses throughout the growing season.

Answer

Soils with a low Cation Exchange Capacity (CEC), such as sandy soils, have a reduced ability to hold onto positively charged nutrients (cations) like potassium and ammonium. This makes them prone to nutrient loss through leaching. Split applications of fertilizer in smaller, more frequent doses ensure that nutrients are available to the crop when needed and minimize the risk of them washing away.

Question 2

Which of the following soil properties has the most significant influence on the availability of nutrients to plants, often referred to as the 'master variable' in soil fertility?

Accepted Answer

Soil pH

Answer

Soil pH is often called the 'master variable' because it directly controls the chemical reactions that determine whether nutrients are in a form that plant roots can absorb. For example, in highly acidic soils, phosphorus can become 'locked up' with iron and aluminum, making it unavailable. Conversely, in highly alkaline soils, micronutrients like iron and manganese become less available.

Question 3

A farmer receives a soil test result showing an optimal pH and adequate potassium levels, but a very low level of organic matter. Which of the following issues is most likely to be a concern for fertilizer management on this field?

Accepted Answer

Poor water infiltration and increased runoff potential.

Answer

Soil organic matter is crucial for creating good soil structure by binding soil particles into aggregates. This improves porosity, which allows for better water infiltration and reduces the likelihood of surface runoff and erosion. Low organic matter can lead to a compacted soil surface, causing water and surface-applied fertilizers to run off the field instead of soaking in.

Question 4

When interpreting a soil test report, the values for phosphorus (P) and potassium (K) are typically listed as 'low', 'optimum', or 'high'. If a soil test comes back in the 'high' range for phosphorus, what is the general recommendation for phosphorus fertilizer application?

Accepted Answer

No phosphorus fertilizer is needed, and application should be avoided.

Answer

A 'high' soil test level indicates that the soil already contains sufficient phosphorus to meet the crop's needs, and adding more fertilizer is unlikely to increase yield. In fact, applying unnecessary phosphorus can have negative environmental consequences, such as contributing to water pollution. Therefore, no additional phosphorus fertilizer is recommended.

Question 5

A certified applicator is preparing to fertilize a field with a heavy clay texture. Compared to a sandy soil, what is a key consideration for managing fertilizer on the clay soil?

Accepted Answer

Nitrogen will be converted to plant-available forms more slowly.

Answer

Clay soils have smaller particles and less pore space compared to sandy soils, which can lead to slower drainage and aeration. While clay soils have a high CEC and can hold nutrients well, fine-textured soils can become compacted and have poor water infiltration. This increases the risk that surface-applied fertilizers, especially phosphorus, can be washed away by rainfall before they can move into the soil profile.

CFA Practice Test

CFA Practice Test

CFA Soil Properties and Testing Questions and Answers