Achieving Tolerable Soil Loss
Introduction
What is T by 2000? ()
The Illinois Erosion and Sediment Control law, often referred to as the T by 2000 program, became effective in April 1980. The law is designed to preserve the long-term productivity of Illinois soil and to protect water quality.
T represents the tolerable soil loss for any specific soil. The term signifies the point at which new soil is naturally produced in greater or equal amounts to that which is lost to erosion. T values range from one to five tons per acre per year, depending on the soil type. The law authorizes the Illinois Department of Agriculture to set erosion control guidelines for reducing soil erosion to T.
Progress towards T()
Year / Below “T”(%) / Slightly over “T”
(%)
1999 / 85.7 / 10.5
2000 / 85.7 / 10.4
2001 / 85.0 / 10.6
2002 / 85.0 / 10.8
2004 / 84.9 / 10.7
2006 / 85.8 / 10.2
Achieving T
The Universal Soil Loss Equation is given by:
A = RKLSCP
Where
A = average annual soil loss in tons per acre per year
R = rainfall and runoff erosivity index for a given location
K = soil erodibility factor
L = slope length factor
S = slope steepness factor
C= cover and management factor
P = conservation or support practice factor
To achieve T, the C and or P factors have to be adjusted such that
CP = T/(RKLS)
EXAMPLE
Determine the most intensive crop rotation for a farmer on a soil with a 400- ft slope length and 8% slope if T for the soil is 3 tons/acre/year. R = 125, K = 0.49, P=0.5, LS = 1.1
C <= T/(RKLSP)
C <= 3/(125x0.49x1.1x0.5)
C <= ?
A farmer near Champaign, Illinois, wishes to grow continuous corn on Drummer Silty Clay Loam while plowing up and down the slope and leaving no residue cover. What is the maximum LS value that will allow the soil loss from the field to be below 2 tons/acre/year. A plot 74 ft. in length on a 9% slope has an LS value of 1.0.
What is the most intense cropping rotation which can be used on a field of Darmstadt soil near Moweaqua having a slope of 5% and a length of 700 ft. The farmer uses chisel plowing and leaves the residue from the previous crop on the field while using contour strip cropping. What would the reduction in soil loss from the field if he uses a terraces to split the slope into two equally wide parts?
A building site near Moline, Illinois, with top soil removed approximates the following condition, C = 1.0. Since no conservation practices are used, P= 1.0. The soil is Stoy , the slope in 5%, and the length is 300 ft. How much erosion would be expected.
A pipeline construction site in the S.W. corner of Springfield, Illinois, will break ground on July 1 and be completed by November 30. The 8% sloping site has a disturbed slope length of 600 ft. The 15 acre exposed area has the following soil characteristics: (silt + very fine sand=40%; sand = 10%; OM = 0%, structure = blocky; permeability = very slow). During construction of the pipeline, the disturbed area will be unprotected after being scraped up and down the slope and compacted with a bulldozer. How many tons of soil is expected to erode from the site?