Applied and Environmental Soil Science

Review Article

Soil Loss Assessment Using the Revised Universal Soil Loss Equation (RUSLE) Model

Table 2

The K factor algorithms.
EquationReferenceSerial number
,
where
A1 = % unstable aggregates less than 0.250 mm
A2 = product of % silt (0.002–0.01 mm) and % sand (0.1–2 mm)
A3 = % base saturation of the soil
A4 = % silt (0.002–0.050 mm)
A5 = % sand (0.1–2 mm)
Units for K: Mg h MJ−1 mm−1		El-Swaify and Dangler [98]13
,
where
K = soil erodibility factor (t hr−1ha−1MJ mm), m = (silt % + sand %) × (100 − clay %)
a = percent organic matter
b = soil structure code: (1) very structured or particulate, (2) fairly structured, (3) slightly structured, and (4) solid
c = soil profile permeability code: (1) rapid, (2) moderate to rapid, (3) moderate, (4) moderate to slow, (5) slow, and (6) very slow
Soil organic matter is derived by the following equation:
SOM = 1.72 ∗ OC [99],
where
SOM = soil organic matter
OC = soil percentage organic carbon content		Wischmeir and Smith [55]14
,
where
SG = coarse sand content (%)
S = sand content (%)
EC = electrical conductivity		Merzoul [100]15
K = 1.292 [2.1 × 10−6fp − 1.14 × (12 − Pom) + 0.0325 (Sstr − 2) + 0.025(fper − 3),
where
K = soil erodibility factor (ton.h/MJ.mm) fp = (Psilt × (100 − Pclay)]
Pom = % organic matter
Sstr = structural code fper = permeability code		Goldman and Wischmeier [101]16
,
where
K is in terms of t ha h MJ−1 ha−1 mm−1
 = geometric mean particle diameter of soil texture		Römkens et al. [102]17
,
where
SAN = sand content (%)
SIL = silt content (%)
CLAY = clay content (%)
C = soil organic content (%)
SN1 = (1 − SAN/100)		Sharply and William [103]18
,
,
where
 = geometric mean diameter of the soil particles (mm)
fi = weight percentage of the particle size fraction (%)
mi = arithmetic mean of the particle size limits (mm)
n = number of particle size fractions		Römkens et al. [104]19
,
,
where
 = Napierian logarithm of the geometric mean of the particle size distribution
OM = organic matter content (%)
Cl = clay fraction (%) fi = mass fraction in the corresponding particle size class (%)
n = number of particle size fractions
di = maximum diameter of the ith class (mm)
di−1 = minimum diameter (mm)		Torri et al. [105]20