A Comparative study of the erodibility of some Malaysian soils
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Date
1996-01
Authors
Osa Stephen, Enoma Agbon
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Abstract
The erodibility factor (K) of ten soil types were determined by laboratory rainfall
simulator, the USLE Erodibility Nomograph and field measurements. The field
measurements were carried out with the sandy loam Bukit Temiang series
using quadruplicated erosion plots of 10 m in length and 2 m in width. The
plots were bare and tilled up and down its uniform slope of 30 percent.
Rainevents, totalling 1,479.3 mm were recorded, out of which 1,015.65 mm
(equivalent to 28 rainevents) were found fo be erosive. The erosive
precipitations were analyzed and soil losses were collected after every
successive rainfall.
The results of the study showed that the 10 soil types were slightly erodible
(irrespective of the method employed), with a measured erodibility factor (K),
ranging from 0.01 to 0.17 mt/j. In the case of the Bukit Temiang series, the
value of the, erodibility factor (K), obtained under direct measurement (field
measurement) indicates that this ·soil type is only slightly erodible (0.02 mt/j).
However, the 100.91 mt/ha soil loss observed in the field for the 28 erosive
rainevents that occured is considered excessive when compared to the annual
tolerable soil loss of 11.0 mt/ha prescribed by the United States Soil
Conservation Service for well drained permeable soils like the Bukit Temiang
series. The outcome of both the field and laboratory studies indicate the
following about the susceptibility of the 10 soil types to water erosion :
(1) Soil erodibility factor (K), has no profound influence on annual soil loss.
(2) Heavy precipitation (Rainfall Erosivity), steeply sloping land and
management are the principal factors affecting yearly soil wash.
Results of N, P and K analysis showed the amount of nutrients leached from
the soil were 156.41 kg/ha for N, 0.016 kg/ha for P and 95.26 kg/ha for K;
these losses, thus account for 70.78 %, 53.33 % and 60.67 % of the total
nutrients available in the soil respectively prior to the setting up of erosion
plots. This finding implies that N, P and K which are required by plants in large
.,.
quantities are highly vulnerable to losses through water erosion. Thus,
cultivation on erosion prone areas like steeplands should be discouraged; as
the cost of replacing lost nutrients with commercial fertilizers may be too great
that it might outweigh the expected reward. '
Earthworm losses were also monitored. Collection of worms were done by
hand-sorting and sieving. The number of earthworms washed from the soil
ranged from 0 to 14,500 .worms/ha for a single rainevent. Earthworm losses
from the soil were highest even at relatively low intensity during single
rainstorms of excessively long duration and at other instances where
antecedent rains fell at close intervals of time; suggesting that earthworms
f
burrow deep into the soil during prolonged periods of drought such as may
occur during intervals of rainfall and migrate to the surface when the soil goes
through another period of protracted saturation. This dynamic characteristic of
earthworms may help improve the infiltration capacity of the soil and reduce
runoff after previous rainfalls that would have compacted the soil and clog
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pores with soil particles. However, the effectiveness of earthworms in
improving soil physical properties depends on the species and the
maintenance of adequate population of earthworms.
Description
Keywords
some Malaysian soils