Land Judging for Farms and Homesites
Definition of Soil Characteristics

Part I

 

I. Surface Texture

The texture of a soil is determined by the relative proportion of clay, silt and sand particles. Coarse- textured soils are sandy. Medium-textured soils contain mainly silt with smaller amounts of sand and clay. Fine-textured soils have a high percentage of clay and less silt or sand. Texture is most easily determined in the field by pressing and rubbing moist soil between the fingers. Unless otherwise stated, textural terms refer to the topsoil. Thus, "Ernest silt loam" means that the surface layer of Ernest soil has a silt loam texture. The texture of the subsoil also should be examined, because it is often different from that of the topsoil and may be a clue to permeability and internal drainage.

Fine-textured - soil is clayey and "slick" or "plastic" when wet. If pressed between fingers and thumb when moist, it forms a thin "leaf" or "ribbon" 2 inches or longer. It will "polish" when rubbed with the flat side of a knife. If worked when too wet, it gets cloddy upon drying and dry clods are hard to break. If organic matter is low, the rate of water intake is slow and water erosion may be serious, even on gentle slopes. Fine-textured soils include clay, silty clay, and sandy clay.  In fine-textured soils, texture is a limiting factor in land use.

Medium-textured - soil feels floury or soft between the fingers. It also can be rubbed into a "leaf" or "ribbon" when moist, but the ribbon is shorter, usually less than 1/2 inch in length, breaks up readily, and will scarcely take a polish. This texture is more desirable than either fine or coarse-textured soils. This type of soil includes clay loam, silty clay loam, sandy clay loam, silt, silt loam, loam, and sandy loam. Medium-textured soil is not a limiting factor in land use.

Coarse-textured - soil feels gritty. It will not "leaf" or "ribbon" and will barely hold together even when wet. It works easily - dry clods are easily broken - but it is a poor plant nutrient supplier. Coarse-textured soil absorbs water readily, but is often droughty because it does not retain much water for plant uptake. If acid, it needs lime more often, but generally not as much at one time as fine-textured soils. Because water moves through this soil rapidly, fertilizer nutrients are easily leached from the soil. Coarse-textured soils include sand and loamy sand. In coarse-textured soil, texture is a limiting factor in land use.

II. Depth of Soil

The depth of soil is determined by the total thickness of soil layers significant to soil use and management. The soil layers or horizons are generally underlain by "parent material" from which the soil developed. Plant roots are normally expected to penetrate the soil layers above the parent material. There are several types of "pans" or layers (such as fragipans or claypans) that restrict root penetration, and air and water movement. These layers, however, should not be considered to limit soil depth. Soil depth is defined as depth to bedrock. If some restrictive layer is encountered in a contest, the judges will provide clues to the contestants. In West Virginia land judging, four soil depth classes are recognized.

Deep Soils - more than 36 inches deep. This is not considered a limiting factor.

Moderately Deep Soils - 20 to 36 inches deep. This is a limiting factor.

Shallow Soils - 10 to 20 inches deep. This is a limiting factor.

Very Shallow Soils - Very shallow soils are those that are less than 10 inches deep. This is a limiting factor.

III. Erosion

Erosion is the detachment and movement of soil from one place to another caused by water and/or wind. Only water erosion is common in West Virginia. The thickness of the original topsoil is given on the field sign so calculation of erosion is possible by determining the thickness of the present topsoil. The following are definitions of erosion classes:

None to Slight Erosion - Less than 25% of the original surface soil (topsoil) has been removed and no gullies are present. This is not considered a limiting factor.

Moderate Erosion - 25% to 75% of the original surface soil has been removed; small gullies may be present; but no large gullies. This is considered a limiting factor.

Severe Erosion - More than 75% of the surface soil has been removed. Considerable subsoil may be mixed in the plow layer. It may have small gullies or an occasional large gully. This is a limiting factor.

Very Severe Erosion - All the original surface soil and part of the original subsoil have been removed. The land may have many small and/or large gullies (>8 inches across) that are actively eroding. This is considered a limiting factor.

IV. Permeability

Permeability refers to the rate at which water and air move through the subsoil. The permeability of a soil is estimated by determining the texture, density, and structure of the most dense and tightest layer in the soil profile (above 36"). Coloration of the subsoil may help in determining permeability but should not be the only indicator used. If restrictive layers are encountered, permeability will be either slow or very slow depending on the properties of the layer. If a fragipan is given on the field sign, the permeability is slow. Four classes of soil permeability are recognized in West Virginia.

Rapid - These soils have coarse or gravelly subsoils with little if any defined structure. There is very little restriction of air and water movement. This is not desirable and is a limiting factor.

Moderate - These soils usually have medium-textured subsoils, have good structure and break apart easily. Clay skins are absent. Water and air movement is good. Plant roots are abundant and penetrate easily through the soil. This is a desirable condition and not a limiting factor.

Slow - These soils have fairly tight, clayey subsoils that have some structure. Some clay skins may be present. These subsoils are firm when moist and hard when dry. Roots are common and may be found along ped faces. Fragipans, if encountered and noted on the field sign, are dense layers with loam or silt textures and are classified as slow. In wet periods the soil may become water-logged. This condition is a limiting factor.

Very Slow - These soils have dense, heavy clay subsoil with little or no structure, and very few visible pores. Clay skins are prominent. After firmly squeezing five to seven times, these subsoils become tough so that pushing your thumb through them is difficult. Roots are few, if they occur at all, and are restricted to ped faces and cracks. Water may stand on the surface of level land or run off and cause erosion on sloping land. This condition is a limiting factor.

V. Internal Soil Drainage

Natural soil drainage refers to the average wetness or dryness of a soil and may be a clue to soil permeability. Soil texture, structure, slope of the land, and absence or presence of a high water table all affect soil drainage. The color of the topsoil and subsoil are clues to internal drainage. Well-drained and moderately well-drained soils have a bright uniform color. They may be brown or various shades of red, brown, or yellow. A pale or washed-out gray color is an indication of poor drainage. A thick black topsoil may also indicate that the land is wet for long periods.

Mottling in the soil (mixed yellow and brown color with some gray spots) is a sign of poor drainage. Rust spots are caused by oxides of iron. Do not misinterpret rust mottling for weathering particles of parent material. The particles of parent material (often sandstone) can be felt between the fingers, while mottles cannot be felt. Color and mottling are easy to see when the soil is moist, but tend to fade when dry. However, they are most easily seen when a sample of well-drained soil is placed beside a poorly-drained one. The depth at which the mottled zone occurs shows the zone of problem drainage, and in general, the closer to the surface the mottling occurs, the poorer the soil drainage. Mottling must also be consistent across the pit. Degrees of internal drainage are:

Well-Drained - Bright uniform color throughout the soil profile (above 36"). This condition is not a limiting factor in land use.

Moderately Well-Drained - Surface soil is a bright uniform color. No mottling (gray spots) occurs above 16 inches from the surface. This is a limiting factor in land use.

Imperfectly or Somewhat Poorly-Drained - Surface horizon (topsoil) is free of mottling. Subsoil is mottled above 16 inches but not in the topsoil or plow layer. If the topsoil is thicker than 8 inches, mottling cannot be found in the upper 8 inches of topsoil. This condition is a limiting factor in land use.

Poorly-Drained - Soil is gray at the surface and has mottling in the topsoil. When topsoil depth is greater than 8 inches, mottling must be observed at or above 8 inches. This condition is a limiting factor in land use.

VI. Surface Runoff

Four classes are recognized in surface runoff, based on the flow of water across the soil surface as determined by slope and characteristics of the soil profile: texture, permeability and internal drainage.

Rapid Runoff - Large amounts of water move rapidly over the surface of the soil. Generally, only a small part moves into the soil profile. For land judging, land with slopes of 8% or more (moderately sloping, or greater) will be classified as having rapid runoff. This condition increases erosion hazards and is a limiting factor in land use.

Moderate Runoff - Applies to surface water when it flows slowly enough that a moderate portion of the water enters the soil. Water puddles on the surface for only short periods. Slope is greater than 1% and is less than 8%. It causes little or no erosion hazard and is not a limiting factor in land use.

Slow Runoff - Applies to water flowing away so slowly that water covers the soil for moderate periods. While this condition causes little or no erosion hazards, it can interfere with soil cultivation. Slow runoff occurs on level land (0 to 1% slope) and is not a limiting factor in land use.

Very Slow Runoff - Applies to surface water more or less standing on the surface for long periods in depressional areas. Water on the surface has no outlet. Most of the water either passes through the soil or evaporates. On coarse-textured soils, water may enter the soil immediately and cause leaching. It interferes with soil cultivation and limits the types of plants which may be grown. This condition is undesirable and is a limiting factor in land use.

VII. Slope

Slope is the number of feet of rise or fall in each 100 feet of land and is expressed in percent. In land judging contests, the area to be measured for slope is marked by two, four-foot, wooden surveyor's stakes driven in to the same height. In West Virginia, the slope stakes are always placed 50 feet apart. No mechanical levels may be used in land judging contests. To determine slope without instruments, place yourself 15 to 20 feet to the downhill side of the slope line made by the slope stakes. Use a straight edge (clipboard or scorecard) or your finger tips.

If you use a straight edge, hold the edge with the finger tips of both hands, clamping your elbows to your body, and sight the edge on the bottom of the higher stake. Turn your body from the waist, holding your arms and straight edge in a rigid position, until you can sight across the lower adjacent stake. At this point, you estimate the height from ground level to the highest point you estimated on the lower stake, and from there arrive at the percent slope.

If you use your arm, place yourself in the same position  (15 to 20 feet downhill of slope line) and extend one of your arms until you can sight over your finger tips to ground level at the higher stake. Then holding your arm rigid, turn your body from the waist until your line of sight is directly on the lower stake. Again, estimate the distance from ground level to the point you estimated on the lower stake. Judging slope correctly requires a great deal of practice. Slope classes are:

A) Nearly level - Less than 3 feet rise or fall in each 100 feet or 0-3% slope. This condition is not a limiting factor.,
B) Gently Sloping - 3 to 8 feet in each 100 feet or 3-8%. This condition is a limiting factor.
C) Moderately Sloping - 8 to 15 feet in each 100 feet or 8-15%. This condition is a limiting factor.
D) Strongly sloping - 15 to 25 feet in each 100 feet or 15-25%. This condition is a limiting factor.
E) Steep - 25 to 35 feet in each 100 feet or 25-35%. This condition is a limiting factor.
F) Very Steep - More than 35 feet in each 100 feet or over 35%. This condition is a serious limiting factor.

VIII. Flood Hazard

Flooding hazard is a term related to land along streams which is subject to occasional or periodic overflows (floodplain or bottomland). For agricultural land use purposes, flooding hazards are grouped in three classes. Flood hazards are given on the field sign.

None to Slight - Floods less than one year out of four. This is not a serious limitation to agricultural use and is not a limiting factor.

Occasional or Moderate - Floods one or two years in four. While this is not too serious, it may be considered a hazard and is a limiting factor.

Frequent or Severe - This land floods often; more than two years in four. It is a severe hazard and is a limiting factor.

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