Soil Science and Testing Flashcards

A soil test reports a cation exchange capacity (CEC) of 25 meq/100g. What does this indicate about the soil's nutrient-holding ability?

Answer: High nutrient-holding capacity

A CEC of 25 meq/100g is considered high, meaning the soil can hold large amounts of positively charged nutrients like calcium, magnesium, and potassium.

Which soil texture class typically has the highest water-holding capacity?

Answer: Clay loam

Clay loam soils have a high proportion of fine particles with large surface area, allowing them to retain significantly more water than coarser-textured soils.

When a soil test shows high phosphorus levels, a fertilizer applicator should:

Answer: Reduce or eliminate phosphorus fertilizer applications

High soil phosphorus levels indicate no additional phosphorus is needed; over-application leads to runoff pollution and wasted resources.

What is the primary purpose of measuring soil electrical conductivity (EC)?

Answer: To estimate soil salinity and ion concentration

Soil EC measures the ability of soil to conduct electrical current, which directly correlates with dissolved salt concentration and overall ion content.

A soil with a high silt content is most prone to which problem?

Answer: Surface crusting and reduced water infiltration

Silt particles are small but lack the cohesion of clay, making silt-dominated soils prone to surface crusting when wetted and dried repeatedly.

Which nutrient becomes less available to plants as soil pH rises above 7.5?

Answer: Iron

Iron solubility decreases sharply at high pH, often causing iron chlorosis (yellowing) in plants grown in alkaline soils.

Soil organic matter content is best improved over the long term by:

Answer: Adding cover crops and crop residue

Cover crops and returning crop residue to the soil consistently add carbon and support microbial activity, building organic matter over time.