1. Surface texture
Soil texture refers to the percentage by weight of sand, silt and clay in a soil. Depending on how
much sand, silt, and clay are present, the soils are given names like sandy loam, clay loam, or silty clay
loam.
Texture is an important soil property because it is closely related to many aspects of soil behavior.
The ease of tilling and plant root development within the soil are both influenced by soil texture. Texture
affects the amount of air and water a soil will hold and the rate of water movement through the soil.
Plant nutrient supplies are also related to soil texture. Tiny silt and clay particles provide more mineral
nutrients to plants than large sand grains. Sandy soils require a high level of management to improve their
productivity; they require more fertilizer and more frequent irrigation or rain than other soils.
This answer is found in the description of the surface horizon. Some soils may contain
multiple A horizons. This question refers to the first or top horizons.
2. Chert and gravel content of surface layer (The topmost A Horizon)
The surface layer is taken into account with this question. Soil texture in relation to the content
of rock fragments greatly affects the plant growth through limiting available water holding
capacity. This also affects bearing capacity of the soil for heavy traffic areas and locations for
water and feeding areas. The chert and gravel content of the surface layer also dictates the seeding
and harvesting methods and ease of tillage.
The chert and gravel content in the horizons below the topmost horizon is taken into account
with the available water holding capacity and therefore will not be included in this answer.
The chert and/or gravel content of the surface layer is found in the description of the topmost A
horizon. The amount is recorded as a modifier to the soil texture and also listed with the percentage
of each kind of rock later in the description.
3. Slope (between 50’ stakes in field)
Slope affects the use and management of the soil. It is directly related to the soil erosion
hazard, and it influences a farmer’s choice of crops and conservation practice. Slope refers to the
steepness of the land surface. Slope is measured in percent calculated as the amount of vertical
change in elevation over some fixed horizontal distance. In this case the slope is estimated between
two stakes at or near the fifty by fifty foot plot.
4. Depth of soil (or zone) limiting rooting depth.
Restrictive layers are slowly permeable and water tends to build up above them. They also
restrict roots from penetrating through them. Because these layers are so slowly permeable, water
does tend to build up above them, creating perched water tables. Perched water tables are temporary
and their presence is usually indicated by gray colors or mottling just above and in the upper part of
the restrictive layer. These soils tend to be more susceptible to drought due to the lower available
water holding capacity.
Limiting layers include fragipans or bedrock. Fragipans are denoted with an x in the horizon
lettering (some examples include: Btx, Ex, etc…). Bedrock will be denoted as a Cr for soft or
weathered bedrock or R for hard bedrock such as limestone, sandstone, or dolomite.
5. Drainage class.
Drainage class refers to the frequency and duration of periods of saturation or particle saturation
during soil formation. Drainage class affects the adaptation of forages to the soil. See chart on page
39.
Answer found on soil interpretation sheet.
6. Depth of topsoil layers (all the A Horizons)
The surface layers are usually denoted with an Ap or A. The depth of these horizons indicates
the soil quality and productivity in the plant root zone. The deeper the topsoil the more productive
the soil usually is.
7. Permeability of most limiting layer or to 60 inches.
Permeability refers to water movement through the soil, specifically the rate at which a
saturated soil transmits water.
This figure should come from the permeability chart on the soil interpretation sheet. Each
horizon has its permeability listed. The slowest permeability (In/Hr range) above bedrock (Cr or R
horizons) should be used (the most limiting layer).
8. Available water capacity to most limiting layer (fragipan or bedrock) or to 60 inches.
Available water capacity (AWC) is the potential of a soil to hold water in a form available to
plants. Since the soil provides the only reservoir of water from which plants can draw, the size or
volume of the reservoir is one of the most important properties of the soil. Soils that have a high
AWC have a greater potential to be productive than soils with a low AWC.
Figure the available water capacity from the chart on the soil interpretation sheet. Each layer
has the range given. Average the range and multiply by the inches in the horizon. If the last
horizon extends beyond 60 inches, only calculate to sixty inches. Add all horizon figures together to
60 inches or to the top of the root limiting layer to arrive at the answer. See page 38 for an example
calculation.
9. Land capability class
Land capability classification shows, in a general way, the suitability of soils for most kinds of
field crops. The soils are grouped according to their limitations for field crops, the risk of damage
if they are used for crops and the way they respond to management.
The numerals indicate progressively greater limitations and narrower choices for practical use.
Answer is found on the soil interpretation sheet under Land Capability Classification.
10. Major factors, if any, that keep area out of Class I
In class I there are no subclasses because the soils of this class have few limitations. Soil
limitations are indicated by the letters e,w,s. “e” indicates erosion potential, “w” indicates wetness
and/or flooding, and “s” indicates shallow, stony, or droughty soils.
Answer is found on the soil interpretation sheet under Land Capability Classification.
FORAGE ADAPTATION
Determine which forages are adapted to the site according to the chart in the Study Guide page 39.
EXAMPLE PROBLEM: Soils Scorecard
The following is an example problem. The soil series description was taken from the Greene and Lawrence County Soil Surveys. The answers for the Scorecard have been marked on the following soil series description [0-X] with the appropriate number representing the questions on the Contest Soils Scorecard.
CLAIBORNE SERIES
The Claiborne Series consists of deep [4-A], well drained [5-E], moderately permeable soils [7-D] formed in local alluvium or residuum of cherty limestone. These soils are on foot slopes and high terraces along the major streams. Slopes range from 2 to 9 percent.
Claiborne soils are similar to Ashton soils and are commonly adjacent to those soils and to Hartville and Viraton soils. Ashton soils contain fewer coarse fragments in the solum than the Claiborne soils. Also, they are lower on the landscape. Hartville soils are somewhat poorly drained. Viraton soils have a fragipan.
| Typical pedon of Claiborne silt loam [1-C], 2 to 5 percent slopes. |
| |
| Ap-- | 0 to 6 inches [6-B]; dark brown (10YR 3/3) silt loam [1-C]; weak very fine granular structure; very friable; many fine roots; slightly acid; abrupt smooth boundary. |
| B1-- | 6 to 14 inches; reddish brown (5YR 4/4) silty clay loam; weak fine subangular blocky structure; friable; many fine roots; few fine pores; medium acid; clear smooth boundary. |
| B21t-- | 14 to 18 inches; yellowish red (5YR 4/6) silty clay loam; weak fine subangular blocky structure; friable; few fine roots; few very fine pores; many black stains (iron and manganese oxide); strongly acid; clear smooth boundary. |
| B22t-- | 18 to 29 inches; red (2.5YR 4/6) and dark red (2.5YR 3/6) silty clay loam; weak medium subangular blocky structure; firm few fine roots; thin patchy clay films on faces of peds few very fine pores; many black stains (iron and manganese oxide); about 5 percent chert fragments; strongly acid; clear smooth boundary. |
| B23t-- | 29 to 41 inches; mottled dark red (2.5YR 3/6) and yellowish red (5YR 5/6) silty clay loam; weak medium subangular blocky structure; firm; few fine roots; few very fine pores; very black stains (iron and manganese oxide); light gray (10YR 7/2) silt coatings on about 10 percent of the peds; about 5 percent fine chert fragments; strongly acid; clear smooth boundary. |
| B24t-- | 41 to 60 inches; mottled dark red (2.5YR 3/6) and yellowish red (5YR 5/6) silty clay loam; moderate very fine subangular blocky structure; few fine roots; few fine pores; very black stains (iron and manganese oxide); light gray (10YR 7/2) silt coatings on about 10 percent of the peds; about 5 percent chert fragments; very strongly acid. |
The solum ranges from 60 to 100 inches in thickness. Its content of angular chert fragments ranges, by volume, from 0 to 25 percent.
The A Horizon has hue of 10YR, value of 3, and chroma of 2 to 4. The B horizon has hue of 7.5YR, 5YR or 2.5YR, value of 3 to 5, and chroma of 4 to 8. It is dominantly silt loam to silty clay but ranges to clay in the lower part.
[3-B] Slope of field - For purposes of this contest, two flags or stakes will be set in the field near the 50 X 50 foot plot. The student will determine the slope using the appropriate calculations.
PH Site 4.9--Surface layer
PH range 4.5 -- 6.0
| Soil Water Holding Capacity |
| SOIL DEPTH (IN.) | AVAILABLE WATER CAPACITY IN./IN.
(Use Average) |
| 0 - 17 | 0.17--0.21 [8-D] |
| 17 - 46 | 0.17--0.20 |
| 46 -60 | 0.17--0.20 |
| Capability Class |
| SLOPE | CLASS
| | 2-- 5% | 2E [9-B & 10-C] |
| | 5--12% | 3E |
| 12--20% | 4E |
| 20--45% | 6E |
| Solution To Problem [8] |
| SOIL DEPTH (IN.) | AVAILABLE WATER CAPACITY IN./IN. |
| 17" | X | .19 | = | 3.2 inches |
| 29" | X | .185 | = | 5.4 inches |
| 14" | X | .185 | = | 2.6 inches |
| 60" | TOTAL | | 11.2 inches |
The following "Forage Adaptation by Soil Drainage Class" table will be used to determine the suitability of this particular soil for each of the forages listed on the Scorecard.
FORAGE ADAPTATION BY SOIL DRAINAGE CLASS
| |
Very Poorly Drained |
Poorly Drained |
Some-what Poorly Drained |
Mod. Well Drained |
Well Drained |
Some-what Excess Drained |
Excess Drained |
| Alfalfa |
|
|
|
X |
X |
X |
|
| Annual Lespedeza |
|
|
|
X |
X |
X |
X |
| Birdsfoot Trefoil |
|
|
X |
X |
X |
X |
|
| Red Clover |
|
|
X |
X |
X |
X |
|
| White or Ladino Clover |
|
|
X |
X |
X |
|
|
| Brome-grass |
|
|
X |
X |
X |
|
|
| Big Bluestem |
|
|
X |
X |
X |
X |
|
| Tall Fescue |
|
X |
X |
X |
X |
X |
X |
| Indian- grass |
|
|
X |
X |
X |
X |
X |
| Orchard-grass |
|
|
|
X |
X |
X |
|
| Switch-grass |
|
X |
X |
X |
X |
X |
X |
| Timothy |
|
|
X |
X |
X |
X |
|
| Caucasian Bluestem |
|
|
|
X |
X |
X |
X |
| Bermuda-grass |
|
|
X |
X |
X |
X |
X |
| Little Bluestem |
|
|
|
X |
X |
X |
X |
| Kentucky Bluegrass |
|
|
X |
X |
X |
X |
X |
| Reed Canary-grass |
X |
X |
X |
X |
X |
X |
|
Return to Grassland Evaluation Contest Study Guide
|