Soil Properties and Testing Flashcards

Which soil horizon is typically where the most weathering, leaching, and organic matter accumulation occurs?

Answer: A horizon

The A horizon (topsoil) is the zone of maximum organic matter accumulation and biological activity.

Soil with a high clay content tends to have what effect on fertilizer application timing?

Answer: Nutrients are held longer, allowing single large applications

Clay soils have high CEC and hold cations longer, reducing leaching and allowing less-frequent nutrient applications.

A grower applies lime to raise soil pH. Which property of lime determines how quickly it reacts in soil?

Answer: Fineness (particle size)

Finer lime particles have greater surface area and react faster with soil acidity than coarser particles.

The term 'cation exchange capacity' (CEC) describes:

Answer: The total negative charge sites available to hold positively charged ions

CEC measures the quantity of cations a soil can adsorb and retain on its negatively charged surfaces.

Which soil property most directly determines the buffering capacity against pH change?

Answer: CEC and organic matter content

Soils with high CEC and organic matter resist pH changes because they can adsorb or release H⁺ ions.

A producer notices iron chlorosis in soybean on a field with pH 7.8. The most probable cause is:

Answer: Iron becoming unavailable due to high pH converting it to insoluble forms

At high pH, iron oxidizes to Fe³⁺ hydroxides that are largely insoluble and unavailable to plants.

Soil respiration measurements are used in soil testing to assess:

Answer: Nitrogen mineralization potential and microbial activity

Soil respiration (CO₂ release) reflects microbial activity, which drives organic matter decomposition and nitrogen mineralization.