The relationship between soil erodibility, which is hard to measure, and modeled infiltration rate were
rarely researched. Here, the soil erodibility factors (
K
and
K
e
in the USLE,
K
i
and
K
1
in the WEPP) were cal-
culated and the infiltration rates were modeled based on the designed laboratory simulation experiments
and proposed infiltration model, in order to build their relationship. The impacts of compost amendment
on the soil erosion characteristics and relationship were also studied. Two contrasting agricultural soils
(bare and cultivated fluvo-aquic soils) were used, and different poultry compost contents (control, low
and high) were applied to both soils. The results indicated that the runoff rate, sediment yield rate and
soil erodibility of the bare soil treatments were generally higher than those of the corresponding culti-
vated soil treatments. The application of composts generally decreased sediment yield and soil erodibility
but did not always decrease runoff. The comparison of measured and modeled infiltration rates indicated
that the model represented the infiltration processes well with an N–S coefficient of 0.84 for overall treat-
ments. Significant negative logarithmic correlations have been found between final infiltration rate (FIR)
and the four soil erodibility factors, and the relationship between USLE-
K
and FIR demonstrated the best
correlation. The application of poultry composts would not influence the logarithmic relationship
between FIR and soil erodibility. Our study provided a useful tool to estimate soil erodibility.