Abstract:
In this study, a laboratory experiment was conducted to evaluate the impact of different soil
amendments on soil erosion parameters of Regosol using simulated rainfall at medium (8%)
and steep (17%) slope gradient. The tested soil sample (Regosol) was collected from cultivated
la
nd of the Kecha watershed (found at Lake Tana basin) and the experiment was conducted using
simulated rainfall available at College of Agriculture and Environmental Science, Bahir Dar
University. After air-drying the experimental soil sample, equivalent rates of 40kg/ha, 2 t/ha, and
4 t/ha of Polyacrylamide (PAM), lime, and gypsum were applied to the soil, respectively. The box
packed with soil was subjected to rain intensity and raindrop size of 11 mm/hr and 2 mm,
respectively. During the first storm and the subsequent five storms, four response variables
(time to runoff, infiltration, surface runoff, and soil loss) were collected at 10 minute interval,
throughout the 30 minute rainfall duration and soil moisture content was also evaluated in
each storm. The collected data were analyzed using SPSS software and MS-Excel. The result
showed that time to runoff (TRO) was significantly (P <0.05) affected by gypsum treatment
while other soil amendments didn’t have significant impact on TRO when compared with the
control treatment. However, infiltration was highly significantly (P <0.01) affected by PAM,
PAM+lime, PAM+gypsum, lime, and gypsum treatment compared with control treatment. The
cumulative runoff was reduced by (23%, 25%) for PAM, (20%, 21%) for PAM+gypsum,
(17%, 20%) for gypsum, (10%, 17%) for lime, (19%, 22%) for PAM+lime treatment at 8%
and 17% slope respectively, compared with the control treatment. Compared to the control,
the total soil loss was reduced by 50% & 53% for PAM, 45% & 49%) for PAM+gypsum, 28%
& 34% for gypsum, 22% & 25% for lime, 49% & 51% for PAM+lime treatment at 8% and
17% slope gradient, respectively. All soil amendments appeared to increase soil moisture
content, thus helping the soil's aggregate stability as well. Therefore, soil amendments
particularly PAM and combined application of PAM with gypsum or lime could be used as an
alternative way to minimize soil erosion for sustainable land management practices.