2023 Iowa FFA Soil Judging CDE Exam Review

Flashcards covering questions and verified correct answers from the 2023 Iowa FFA Soil Judging CDE Exam.

What depth of redox feature concentrations with no depletions present indicates a moderately well drained soil?

40 inches

Which practices are considered TIER 1 conservation practices?

Reduced tillage and contour tillage

Which soil characteristics make a soil best suited for treatment of effluent in a septic tank absorption field?

Upland landscape position and well drained soil

How is a topsoil thickness of 9.5 inches of A horizon before a B horizon classified?

Moderately thick

Which conservation practice prevents rills and gullying in places where water flows quickly through soil drainageways?

Grass waterways

Which surface drainage class applies when water escapes across the soil surface slowly due to nearly level slope, rough surface, or vegetation?

Slow

Which soil order is formed under prairie vegetation, adding significant organic material to depths beyond the surface layer?

Mollisol

In Iowa, a slope of 4% belongs to which slope group?

B Slope

Which factors influence soil color?

Moisture status, organic matter, and drainage class

What is the practice of planting strips of a small grain crop across a slope to catch erosion coming off a crop like corn?

Strip cropping

What is the parent material of a soil dominated by mostly silt-sized material with a uniform profile and little to no apparent layering?

Loess

Why is water-logged soil likely to prevent the growth of plant roots?

Lack of oxygen

What is the most common range for soil depths in Iowa?

Between 30 and 70 inches

How is land with a 5-14 percent slope that can grow normal crops with a rotation of soil-conserving crops classified?

Class III

Which soil structure consists of roughly spherical aggregates commonly found in A horizons with higher organic matter?

Granular

Which subsoil colors indicate that a soil is well aerated?

Brown and yellowish brown

Which soil structure of the A horizon indicates the poorest soil health?

Platy appearance due to compaction

What is residuum parent material?

Parent material formed in place by the weathering of bedrock into a disintegrated mass

What are the key functions and adaptations of terraces?

They reduce erosion by shortening the effective slope length and are best adapted where slopes are long and relatively uniform.

What specified conditions apply to the assignment of Corn Suitability Ratings for soil map units in Iowa?

Natural weather conditions (not irrigated) and surface and subsurface drainage installed where needed

Which landscape position is a remnant of a former floodplain?

Stream Terrace

What is the order of preference to identify land capability subclasses if two or more limitations exist?

Erosion, Wetness, Soil

Which erosion class describes land whose use potential is significantly reduced by erosion?

Severely eroded

What is the minimum depth to hard bedrock required so that hard bedrock is not a limitation when evaluating building sites for houses with basements?

At least 60 inches

Which horizon is described as a light-colored zone with decreased clay?

E Horizon

Which soil separate has the lowest number of particles per gram?

Course Sand

In which landscape position are the oldest and most strongly developed soils generally found?

Upland

Which soil structures are characteristically significantly wider than they are tall?

Platy

What is the primary difference between an Entisol and an Alfisol?

An Alfisol has a Bt horizon whereas an Entisol does not

Which physical features indicate a healthy soil?

Stable aggregates and an A horizon with granular soil structure

How is a soil with a profile depth of 38 inches before bedrock classified?

Moderately Deep

What does an Ap horizon designation likely represent?

The surface layer of a cultivated field

What facts are true regarding native soil vegetation?

Transition soils result from grass and trees, forest soils are usually more acidic than prairie soils, marsh soils include reeds, sedges, and cattails, and forest soils typically feature a thin A horizon underlain by an E horizon.

What is the calculated slope of a hill when the elevation drops 1.5 feet over 25 feet of run?

$$6\%$$