Soil Conservation Experiments on Cultivated Land in the Maybar Area, Wello Region, Ethiopia•
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Date
1988-06
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Addis Ababa University
Abstract
Soil conservation experiments consisting 6 plots (five of them
treated and one untreated control plot) were established in 1986 in
the Maybar area to identify the most suitable soil conservation
measure(s) for the area and other similar areas in Wello region. The
plots (each 30m long and 6m wide) are placed side by side on a 28%
slope with a well-drained, highly stony, HAPLIC PHAEOZEM of about 60
cm depth . The treatments are Level Bund, Graded Bund, Level Fanya
juu, Graded Fanya juu and Grass Strip.
Soil loss and runoff measurements from the experimental plots
were made during 65 rainfall events with a total rainfall amount and
erosivity (EI30) of 2098mm and 876 Joules m- i h- i , respectively. 41
of the 65 rainfall periods having a total rainfall amount and EI30
value of l29lmm and 516 Joules m- i h- i respectively were monitored in
1986. The rest (24 rainfall events with rainfall amount and EI30 of
8Q7mm. and 360 Joules m- i h .- i , respectively) occurred in 1987.
The observed annual soil loss values from all experimental plots are
below the tolerance level.
between experimental plots.
Yet, significant differences exist
The graded Bund showed distinctivelyhigher soil loss in both 1986 and 1987 amounting to 5.15 tons/ha and
1 . 66 tons/ha, respectively. The t hree level soil conservation
measures (Level Fanya juu, Grass Strip and Level Bund) consistently
showed significantly lower annual soil loss values in both the years
amounting to 0.49, 0 . 84 and 1.04 tons/ha, respectively in 1986 and to
0.15, 0.40 and 0.54 tons/ha in 1987. The control plot showed an
annual soil loss of 2.02 tons/ha (which was less than half of the
annual soil loss of the Graded Bund) in 1986 and of 1 . 1 tons/ha in
1987 .
Crop cover (as the major factor), high surface stoniness of the
experimental plots which encouraged infiltr ation of rainwater into
the soil and the dominance of low - erosivity rains during the study
period were observed to have resulted in very low soil losses during
individual rainfall events .
Under the rainfall conditions observed in 1986 and 1987, vegetative
cover together with the high surface stoniness on the experimental
plots have been sufficient to reduce soil loss from the plots to
values below the tolerance level. However, soil loss data collected
from test plots in the Maybar area showed that extreme years will
produce upto 100 times more erosion than during the study period.
As a result of the experiments, it is concluded that in the Maybar
area and in the whole eastern escarpment of Wello, the choice should
be for agronomic soil conservation measures . These have to be
supported by physical soil conservation measures (Level Fanya juu,
Grass Strip a nd Leve l Bund) on steep slopes (15 to 50%) since test
plot data have shown that extreme years will result in soil losses
much higher than those observed during the study period. However,
even where the physical meaures are applied, the stress should be on
reducing inter-terrace erosion by means of agronomic measures
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Keywords
Soil Conservation Experiments on Culti Vated Land