Soil erodibility (K) factor in the Universal Soil Loss Equation (USLE), defines the resistance of soil to detachment by rainfall impact and/or surface flow force. Whilst there are a number of factors of erosion, this study aims to use erodibility factor and related length slope factor to assess soil erosional loss at field scale. To quantify soil erodibility the following properties were measured; texture, organic matter content and structural properties of the soil samples in eroded and non-eroded sites. Sub sampling was conducted in both eroded and non-eroded site and a total of six samples were collected in each site. In addition, slope length and slope angle were determined to evaluate the slope effect on the degree of soil loss associated with the K-factor. The measured or estimated K-factor value compared with the USLE K-based nomograph. The average soil erodibility (K-factor) was 0.031 and (t ha h ha-1 MJ-1mm-1 ) for eroded and non-eroded area, respectively. The high K-factor value in eroded area (almost doubled) was associated with low organic matter content (0.75%) compared to high organic matter in non-eroded (1.18%) as well as the significant slope (3°) in eroded than non-eroded areas (1°). The results also show that K-factor significantly (P<0.05) correlates with soil texture and organic matter due to their strong binding effect on aggregate stability and water infiltration hence enhanced particles’ resistant to detachment. Interestingly there was no significant difference in K- factor values between eroded and non-eroded areas. Further, the K-factor based nomograph over-predicted the measured K-factor value by 10 times in eroded and 19 times in non-eroded soil, with a strong correlation in eroded (r2 =0.77) than in non-eroded (r2 =0.10).
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Manyiwa et al. (2013) studied this question.