Abstract:
comer of the Melka Sedi Banana Farm, and in the southern part of
the Amibara irrigation project (Fig.l). The scheme was constructed
in 1983, on 35 ha of land and operation commenced in the same year.
Monitoring work was also started just after the completion of the
scheme and preliminary results were presented in a report (7).
The site was characterized by high temperature and low humidity,
resulting in a considerably high evapotranspiration rate, while the
average annual rainfall is only about 550 mm. This was summarized
from class I weather station at Melka Werer Research Center
(Appendix 4).
The soil of the pilot scheme area was surveyed in 1969 and 1971 by
an Italian consultant as part of the feasibility study for the larger area
of Amibara Irrigation Project. The survey result characterized the area
as layered soils of variable texture, and described generally as nonsaline
and non-sodic. Further surveys were also conducted in 1975
and 1981 (5) including the pilot drainage scheme.
Subsequent surveys with the earlier feasibility studies showed that
the pilot drainage scheme soils are deep, dark-brown and generally
loamy, with a high silt and very fine sand content. They frequently
show textural stratification in theprofile, presumably resulting from
deposition cycles on the Awash flood plain by fluvial activity from
streams draining the escarpment to the south west. Generally a
relative impermeable layer of silty-clay was observed at three meter
depth from the soil surface. Hydraulic conductivity values of the soil
varied from 0.1 to 5 m day'1 (7).
The initial salinity of the area varied from place to place. Ground
water table fluctuated around 1.5 m from the surface of the soil, and
salt concentration ranged from 5 to 35 ds m 1. Part of the scheme was
left fallow for a long period (Field 4c/6 and 4c/10) while the
remaining was under banana plantation, with poor stand (Field 4c/ 7),
before the installation of the drains.
