Question

Estimate the soil loss using the USLE for a square 1-acre plot at a 4% slope for the southwestern corner of Pennsylvania. Assume that the soil is 40% silt plus very fine sand, 10% sand (0.1<d<2 mm),(0.1<d<2 mm), no organic matter, fine granular soil structure, and moderate permeability. Assume a sweet clover meadow with no support practice.

Assume: Topographic Factor Index Length = 150-ft

Note: CORRECT ANSWER IS NOT 0.395 tons/acre/year

Answer 1

Ans) According to universal soil loss equation (USLE),

A = R K (LS) C P

where, A = Annual soil loss in tons/acre/year

R = Rainfall erosivity index

K = Soil erodibility factor

LS = Topographic factor

C = Cropping factor

P = Conservation practice factor

For Pennsylvania, R = 100

For 40% silt with very find sand and no organic matter, K =0.44 tonnes/acre

For 10% sand and noorganic matter, K = 0.03 tonnes/acre

=> Average K = 0.40(0.44) + 0.10(0.03) = 0.179 tons/acre

LS = [0.065 + 0.0456 S + 0.006541] (L / 72.5)^0.4

where.S = Slope(%) and L = Length in ft

=> LS = [0.065 + 0.0456(4) + 0.006541 ] (150 / 72.5)^0.4

=> LS = 0.470

C factor for clover medow = 0.40

For no support practice , P = 1

Putting all values,

=> A = 100 x 0.179 x 0.47 x 0.40 x 1

=> A = 3.365 tons/acre/year