Grassland Evaluation Contest Study GuideFifth Edition: October 2005
Practical Exercises

 
Armstrong Series  
Soil Map Unit 50001
     
Depth class: Very deep Drainage class: Somewhat poorly  
Landform: Uplands Parent material: Loess or loamy sediments over glacial till  
Slope range: 5 to 9 Percent Land Capability Classification: 3E  
     
Soil Depths
(Inches)
Available Water Capacity
(In/in range)
Permeability
(In/hr range)
     
0-6 0.20-0.22 0.20-0.60
6-44 0.11-0.16 0.06-0.20
44-70 0.14-0.16 0.20-0.60

Taxonomic class: Fine, smectitic, mesic Aquertic Hapludalfs

Typical Pedon: Armstrong loam 5 to 9 percent slopes, eroded.

Ap=0 to 6 inches; very dark grayish brown (10YR 3/2) loam; grayish brown (10YR 5/2) dry; mixing of brown (10YR 4/3); weak fine granular structure; friable; slightly acid; abrupt smooth boundary
.
BE=6 to 14 inches; dark yellowish brown (10YR 4/4) clay loam; weak fine subangular blocky structure; friable; thin discontinuous light gray (10YR 6/1) dry silt coatings on faces of peds; strongly acid; clear smooth boundary.

2Bt1=14 to 18 inches; brown (7.5YR 4/4) clay loam; few fine distinct brown (5YR 4/4) and prominent yellowish red (5YR 4/6) mottles; moderate fine subangular blocky structure; firm few thin discontinuous clay films; thin continuous light gray (19YR 6/1) dry silt coatings on faces of peds; stone line at base of horizon; strongly acid; gradual smooth boundary.

2Bt2=18 to 26 inches; mottled brown (7.5YR 4/4) and dark grayish brown (10YR 4/2) clay; few fine prominent red (2.5YR 4/6) mottles; moderate fine moderate fine subangular blocky structure; very firm; thin continuous light gray (10YR 6/1) dry silt coatings on faces of peds; clay films on most peds; some pebbles; very strongly acid; gradual smooth boundary.

2Bt3=26 to 31 inches; mottled strong brown (7.5YR 5/6) and light brownish gray (10YR 6/2) clay; few fine prominent dark red (2.5YR 3/6) and common medium distinct yellowish red (5YR 4/6) mottles; moderate fine subangular blocky structure; very firm; thick discontinuous clay films; some pebbles; strongly acid; gradual smooth boundary.

2Bt4=31 to 44 inches; strong brown (7.5YR 5/6) clay loam; common fine prominent light brownish gray (10YR 6/2) yellowish red (5YR 4/6) mottles; moderate fine prismatic structure parting to weak medium subangular blocky; very firm; few thin discontinuous clay films on peds and in old root channels; black (N/20) organic material on vertical ped faces; common fine black concretions (oxides); strongly acid; gradual smooth boundary.

2BC=44 to 70 inches; yellowish brown (10YR 5/6) clay loam; common fine and medium prominent gray (10Y 6/1) mottles; weak medium prismatic structure parting to weak medium subangular blocky; firm; dark brown clay flows in some channels; common fine black concretions (oxide); moderately acid.

Range in Characteristics: Solum thickness and depth to free carbonates commonly are more than 48 inches but range from about 42 to 80 inches. A stone line or pebble band is at the upper boundary of the subhorizon with highest clay content. Soil reaction ranges from moderately acid to very strongly acid in the most acid part, but ranges to slightly alkaline in the BC horizon where carbonates are present.

Drainage and Permeability: Permeability is slow in the Armstrong soil. Surface runoff is rapid. Drainage is somewhat poorly. A perched water table is at a depth of 1 to 3 feet during most winter and spring months.

Use and Vegetation: These soils are used mainly for hay and pasture but some corn and oats are grown. Native vegetation was mixed prairie grasses and deciduous trees.


Return to Grassland Evaluation Contest Study Guide