Download Agricultural productivity and land degradation

Maria Larsson: Agricultural productivity and land degradation - a study of two
areas in the highlands of Ethiopia.
Abstract - This Minor Field Study was carried out in Ethiopia, March to June 1997. The two
areas of concern are one area in Debre Sina wereda, South Wollo and another in Machakel
wereda, East Gojjam both found in Amhara National Regional State, Ethiopia. The areas are
parts of the Ethiopian Highlands, with an elevation over 1500 meters above sea level. East
Gojjam is a so-called high potential area, compared with South Wollo where the productivity is
extremely low. In East Gojjam there is more rainfall, less steep slopes, but a more erodible soil
type.
The purpose of this study is to compare two areas at different levels in Amhara National
Regional State regarding agricultural productivity, with special emphasis on the physical setting
and the degree of land degradation, as well as conservation measures.
The methods used are analysis of aerial photographs, field observation/mapping, use of GIS for
analyses, analysis of climatic data, and a literature study.
The result of this study shows that:
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The slopes are much steeper in the study area in Debre Sina Wereda and that there are
more people per square meter in the rural areas. The rain period is from June to August,
and the driest months are December and January. The yearly average precipitation is
higher at Debre Markos/Anjeni than at Mekane Selam/Maybar. The longer a rainfall last
the lower the intensity becomes in the two research stations Maybar (South Wollo) and
Anjeni (East Gojjam). The intensity is somewhat higher at Maybar. In Debre Sina, the
soil is mostly brown and black, in Machakel almost all soil is red, and deeper than in
Debre Sina. The soil is, in itself, more suitable for agriculture in Debre Sina than in
Machakel.
The degree of land degradation has visibly changed in some of the gullies since 1980/82,
especially the large gully in the local study area in Machakel. Road drums are a major
contributor to gully erosion in both local study areas. The GIS maps show that there is a
risk for gully erosion in about 50% of the study area.
The farmers are well aware of the occurrence of erosion, as well as what to do about it
(even if they do nothing). The farmers I spoke to in Debre Sina were more interested in
doing conservation measures. The opinion of main constraint for agricultural productivity
in Debre Sina was soil erosion and in Machakel shortage of fertiliser. The productivity is
generally higher in Machakel and the main reason seems to be the use of fertiliser.
The conclusions are:
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The physical setting in Machakel is more favourable for agriculture and the most
important determining factor is the topography. The physical setting is important for
agricultural productivity, but it is not determining.
The degree of land degradation is severe, but this is not a new phenomenon. The severity
of soil erosion is somewhat higher in Debre Sina. Road drums are a major contributor to
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gully erosion in both areas. I consider soil erosion to have a negative impact for
agricultural productivity, especially in the long run. Among the physical factors, the most
important for soil erosion is the velocity of the water, followed by vegetation.
The productivity is generally higher in East Gojjam/Machakel, the main reason is the use
of fertiliser. The farmers feel that the productivity is declining.
The farmers in Debre Sina, where the need has been larger, were more interested in doing
conservation measures.
Earth Sciences Centre, Göteborg University
Publ. B128 1998 , ISSN 1400-3821