Keystone & Writing Assignment #1 Flashcards
You determined a slope of 5.83% and a slope length of 143 feet in your field. Use the LS table and determine the LS factor for these field conditions conservatively!
0.823
Interpolated LS-factor
You determined a slope of 1.02% and a slope length of 63 feet in your field. Use the LS table and determine the LS factor for these field conditions.
0.184
R values
You work on a conservation plan for a farm in Hale County in Alabama.
What is the R-value for this county?
375
Soil Loss Conventional Tillage Corn
On your farm in Mobile County, you farm a field conventionally, and you plan to grow corn as a continuous crop (early planted, spring plow, chiseled) with residue left on the field. You determined a slope of 5.53% and a slope length of 44 feet in your field. Use the LS table and determine the LS factor for these field conditions conservatively! Your soil has a soil erodibility factor K factor of 0.43, and you expect a yield of 52 bushels per acre. Estimate the annual soil loss if no additional erosion control practice (P factor) is implemented.
A=RKLSCP
R = 550
K = 0.43
LS = 0.475
C = 0.27 (Table 3.1A)
P = 1
A = 550 x 0.43 x 0.475 x 0.27 x 1 = 30.33
Weighted Slope Average
You determined a transect in the field. The transect has 3 different slopes. You measured the individual slope lengths as 58, 49, 79 (in feet), and the corresponding slopes were 1, 4.9, 1.4 (in percent).
Compute the weighted slope average.
Soil Loss Conservation Tillage Corn
On your farm in Washington county, you farm a field with conservation tillage, and you plan to grow corn as a continuous crop, early planted. You estimate the minimum surface residues to be 50%. You determined a slope of 3.92% and a slope length of 43 feet in your field. Use the LS table and determine the LS factor for these field conditions conservatively! Your soil has a soil erodibility factor K of 0.34, and you expect a yield of 68 bushels per acre.
Estimate the annual soil loss if no additional erosion control practice (P factor) is implemented.
A=RKLSCP
R = 475
K = 0.34
LS = 0.303
C = 0.16 (Table 3.1A)
P = 1
A = 475 x 0.34 x 0.303 x 0.16 x 1 = 7.83
Terracing
You want to decrease the annual soil loss on your farm, and you consider terracing your field. You determined an annual soil loss of 16.2 tons per acre and year. The horizontal interval would be less than 110, and outlets would be closed.
Predict the annual soil loss in tons per acre and year if the terraces were implemented as outlined above.
A = RKLSCP
RKLSC = 16.2 ton/a/y
P = 0.5
A = 16.2 x 0.5 = 8.1 ton/a/y
Curve Number Method
You use the NRCS curve number method to estimate the runoff from bare soil (hydrological group D) with a CN value of 94. You observed rainfall with a precipitation depth of P=2.9 inches.
Use the formula for the curve number method to estimate the runoff in inches.
CN = 94
P = 2.9
S = (1000/CN) - 10
S = (1000/94) - 10 = 0.638297
Q = (P-0.2S)^2 / (P+0.8S)
Q = (2.9-(0.2)(0.638297)^2) / (2.9+(0.8)(0.638297))
Q = 7.68587/3.4106376 = 2.25
Terracing
You want to decrease the annual soil loss on your farm and consider terrace and contour farming your field. You determined an annual soil loss of 24 tons per acre and year. For the terraces, the horizontal interval would be 140 - 180, and outlets would be closed. For contour farming, you determined a P value of 0.85.
Predict the annual soil loss in tons per acre and year if the terraces were implemented as outlined above and the field was farmed on contours.
A = RKLSCP
RKLSC = 24 ton/a/y
P = 0.85 (Contour)
P = 0.7 (Terrace)
A = 24 x 0.85 x 0.7 = 14.28
What is the maximum mineral particle diameter in mm which is considered in textural groups?
2
Check the soil texture triangle. What texture class is a soil which has 30% clay and 35% sand?
Clay loam
Silt loam
Loam
Clay
Clay loam
The soil texture classes were created…
The Unified Soil Classification System…
to describe the agricultural productivity of soils.
was created to describe soils for geotechnical purposes.
The soil texture classes were created to describe the agricultural productivity of soils.
The Unified Soil Classification System was created to describe soils for geotechnical purposes.
In the Unified Soil Classification System, what percentage of soils do have pass a No 200 sieve in order to be classified as fine-grained soils?
exactly 50%
more than 40%
more than 50%
more than 60%
more than 50%
Match the soil orders to the descriptions”
Oxisol -
Andisols -
Gelisols -
Ultisols -
older soils, warm, humid climate
volcanic materials
cold climates
extremely old soils, hot, humid climate
Oxisol - extremely old soils, hot, humid climate
Andisols - volcanic materials
Gelisols - cold climates
Ultisols - older soils, warm, humid climate
___ is the dominating soil order in the Southeastern US!
Ultisol
