Soil Science and Testing Flashcards

A grower's soil test shows a base saturation of 65% calcium, 12% magnesium, and 4% potassium. What does this suggest?

Answer: Potassium is deficient and magnesium may be high

Optimal potassium base saturation is typically 2–5%, but 4% combined with 12% Mg suggests magnesium may be competing with potassium uptake, and potassium should be monitored.

Which method is used to determine the soil texture class in the field without lab equipment?

Answer: Ribbon and feel method

The ribbon and feel method involves moistening a soil sample and working it between fingers to assess the length of ribbon formed, estimating sand, silt, and clay content.

Soil bulk density is used to assess:

Answer: Degree of soil compaction

Bulk density measures the mass of dry soil per unit volume, with higher values indicating greater compaction and reduced pore space.

When sulfur is applied to a high-pH soil, the expected outcome is:

Answer: Decreased soil pH over time

Elemental sulfur is oxidized by soil bacteria to form sulfuric acid, which acidifies the soil and lowers pH over time.

The term 'soil profile' refers to:

Answer: A vertical cross-section of soil showing distinct horizontal layers

A soil profile is a vertical section from the surface to the parent material, showing distinct horizons (O, A, B, C) with different properties.

Which of the following best describes a 'perched water table'?

Answer: A localized saturated zone above an impermeable layer

A perched water table forms when water accumulates above an impermeable layer (such as a clay pan or hardpan) before reaching the regional water table.

To convert a soil test phosphorus result from ppm to lbs/acre for a 6-inch sampling depth, you multiply by approximately:

Answer: 2.0

For a standard 6-inch sampling depth, soil weight per acre is approximately 2 million lbs, so ppm × 2 converts to lbs/acre.