|Proceedings of the Khartoum Workshop on Arid Lands Management (UNU, 1979, 96 pages)|
|Case studies from the Sudan|
H.A. R. Musnad Forestry Research Institute-Soba
M.A. el-Rasheed Department of Forestry, University of Khartoum
Although more than half the area of the Sudan is arid and semi-arid, the country's economy is based on agriculture. Under such conditions, soil forms a vital resource that deserves every care. Nevertheless, soil misuse has led and will continue to lead to degradation resulting in desert creep into better areas. Practices like shifting cultivation, uncontrolled grazing, irrational use of machines on light soil, and fires are amongst the most serious factors causing soil erosion.
Agricultural expansion, both public and private, has proceeded without any conservation measures. The consequences have manifested themselves in the form of deforestation, soil desiccation, and lowering of soil fertility and the water-table. These evils gained momentum until they resulted in a drought problem, especially in the west, gully erosion in the Northern Province (Haddam) and the Kerreb lands of Kassala and the Blue Nile, and dune invasion in the western and eastern parts of the country.
Erosion by water remained unchecked in wetter areas and in areas of vulnerable soil. It had spoiled more than 50,000 ha in the el-Suki area alone (Musnad, 1975). The jagged outline of the map of the Rahad Scheme is an attempt to avoid eroded areas. The extent of such damage in the whole country remains unknown.
The literature cited between 1940 and 1975, the time of preparation of the DECARP documents, showed that a large cross-section of the officials dealing with land were well aware of the evils resulting from misuse of soils. Nevertheless, conservation measures were neglected in the majority of land-use activities. The same methods that degraded soils in Agabey and Grabeen, for example, are now being used at Um Sbnat and Habeela. These are new areas deforested for mechanized grain production. Measures such as leaving natural tree belts between farms and round natural drains were not carried out. In these areas gully erosion is now well advanced. The Khashm el-Girba Scheme emerged without adequate shelter belts and wind breaks for its crops and canals. The canals frequently silted up, resulting in severe droughts at stages which adversely affected yield. The Jabel Marra is being exploited by machines with no thought for the light volcanic type of soil or the vulnerable slopes.
Characteristics of the Problem Areas
The previous points mentioned emphasize the need for adequate conservation and reclamation efforts. To plan these efforts soundly, the characteristics of each problem area must be taken into consideration. Each problem area is part of an eco-system composed of soil, water, vegetation, man, animals, and climate. Conservation and reclamation measures will try to influence some or all of these components for the perpetual benefits of man (Musnad, 1970).
At present, data are available on soil type, vegetation, and climatic conditions as well as on the distribution of human and animal populations. Modern aerial photography coupled with satellite imagery constitutes a powerful means of overviewing the problem areas.
Patterns of Soil and Vegetation Misuse
Over-cutting and over-grazing
These activities are quite evident near settlements, where trees and shrubs are widely used for fuel and buildings. The walls and roofs of houses in most of the rural areas are made of wood. These houses are always surrounded with fences made out of wood and hay. The demand for wood for such buildings is continuously increasing as renewals are necessary every two to three years, in addition to new buildings. It is not difficult to see how taxing this practice is on the resource, bearing in mind the light or sparse vegetation cover of the arid and semi-arid zones.
Areas round watering points also suffer the same degree of degradation. These are over-grazed, especially in western Sudan where bore-holes with adequate water exist with pastures of low carrying capacities.
Over-cropping took place and is taking place on clay plains as well as on sandy soils. On clay plains, mechanized agriculture has deforested, impoverished, and turned vast areas into infertile truncated soil-waste known locally as kerreb. The top layer has been washed away by water erosion and the subsoil has assumed the "basket-of-eggs" appearance that encourages maximum run-off. The hydrological behaviour of this formation facilitates further erosion of neighbouring soils and, therefore, the devastation is now self-propagating.
On the sandy soils, over-cropping resulted in shortening the rotation of gum arabic and crops. The ideal rotation for gum arable is 12 to 15 years, after which the trees are felled and annual crops of sesame, groundnuts, and pennisetum, dukhun, are grown for three to four years while the gum coppice is tended. The land will then be under gum production for at least 12 years. The present practice is limited to annual cropping with no gums or a very low stock of gum trees per unit area. This has lowered the yield of annual crops and deprived the soil of tree cover. Soil desiccation, dune movements, lowering of the water-table, burial of surface water systems by moving sands, and drought problems are further consequences of these practice
Grass fires were so common that the term "acacia-grass cycle" was used by many writers to describe the effect of fire on the ecology of clay-plains with rainfall of 50-700 mm. This is now no longer restricted to the Acacia-Graminae community of the clay-plains. Fires now occur all over the country south of latitude 12°N. This is most evident from midSeptember until January. The effects of these fires on the ecosystem and especially on the cycle of nutrients deserve to be studied. The amount of fodder materials that turns into ash can be visualized as equivalent to the loss of tons of meat. The effects of fires on wildlife, plant communities and soilwater relations are also worthy of study.
Present Magnitude of the Problem
First of all, there is appreciable sand dune movement in the arid and semi-arid parts of the country, where wind erosion is a real problem. This buries fertile soil, irrigation canals, roads, railway lines, buildings, seasonal water courses and even river channels. These difficulties are very pronounced in the Northern, Nile, Northern Kordofan, Northern Dafur, White Nile, Khartoum, and Gezira Provinces.
There is severe gully erosion on the clay plains and main river banks. The two words kerreb and haddam are used locally to describe this type of soil degradation.
The wind storms (hababai) of eastern Sudan constitute a special problem. Winds blowing at more than 12 kph over a special type of sandy loam soil cause haasbai. This is a problem of soil management in the first place and of lack of shelter-belts to reduce the wind energy in the second place. To facilitate flood irrigation, the soil must be flat and free from any obstruction to water movement. Crop residue is, therefore, removed after harvest and the soil is left bare to be blown away by wind.
Other problem areas are the saline soils near the Red Sea shore and the partially flooded areas. These are totally neglected in some parts and under-used in others.
Consequences of These Problems
Evident consequences of land degradation problems can be described as follows:
(a) Reduction in yield especially of food crops, which has brought other
difficulties such as social problems of migration to towns, semi-nomadic life,
and occupational change.
(b) Land hunger, because large areas of relatively poor soils are cultivated to get the same yield that could have been obtained from a smaller area of fertile soil. Pasture productivity has also dropped to the degree that carrying capacity has been reduced through invasion of degraded lands by unpalatable plants or by plants with low nutritive value.
The drop in yield and land hunger need to be seen against the relatively high rate of increase of human and animal populations in the country
Present Research Efforts
Completed and current research projects
Research work in Khartoum Province was concentrated on soil moisture conservation for plant growth in the arid climate of northern Sudan. This work was carried out between 1969 and 1971. It involved protection of vegetation from animals and soil-working to improve the water relations of the soil profile. The method proved also very successful for annual grasses and herbs. The tree species used were Tamarix aphylla and Prosopis chilensis. These were introduced into the area together with the locally available Acacia tortilis (Musnad, 1971).
In the Nile Province mesquite (Prosopis chilensis) and Eucalyptus spp. were used as external belts for the protection of crops and irrigation canals. This work is now supported by funds from the Sudanese Council of Churches. With this same support, internal protective belts are also going to be established, especially in new irrigation schemes like Kelley and Gandatu.
A land reclamation research project was started in Northern Province in 1973. It received financial support for the period 1975-1980 from the International Development Research Centre (IDRC) of Canada. This project attempts to identify the most effective type of shelter-belts needed for protection of land and crops against sand creep in the Nubian Desert. This will make more arable land available for a local population suffering from land hunger. Arable lands in this province are restricted to small strips along the banks of the Nile. These lands are, in addition, suffering from erosion on the river side and burial by sterile sand from the desert side. This project further includes a training scheme at the master's level for four young graduates (Musnad, 1977).
In Northern Kordofan a very successful experiment on sand dune fixation was carried out at el-Bashri, north of el-Obeid. The success of the experiment encouraged different institutions interested in this type of work to visit the area. The experimental site shows a clear contrast between well established flora and bare moving dunes which are not protected and planted.
Proposed research projects
The programmes of research prepared by the Arid Zone and Gum Research Divisions of the Forestry Research Institute embrace most of the methods necessary for conservation and reclamation of soil and vegetation. These are long-term programmes that need trained manpower, funds, and equipment.
The IDRC is supporting a research project on Prosopis. This research is being carried out in the White Nile Province (elSheikh and el-Siddig), where rainfall is less than 200 mm, in Northern Kordofan (Hamarat el-Wiz and el-Bashri), where rainfall is more than 200 mm, and at el-Obeid, where rainfall is about 300-320 mm. About 30 eco-types and species of Prosopis are being tried in order to arrive at the most successful, easily established and useful eco-types. This research is being conducted in collaboration with the Faculty of Veterinary Science of the University of Khartoum. The faculty's work is concerned with the fodder value of Prosopis pods for goats and other animals. Many eco-types of Prosopis have the unique characteristic that their green parts are unpalatable to goats and other domestic animals. The ripe pods, on the other hand, contain high percentages of protein and sugar and are generally said to be of high nutritive value. Prosopis timber also has a high calorific value as fuel.
The research project aims at providing fodder and fuel wood and protecting the soil against wind and water erosion. The research methods suggested will attempt to investigate unconventional techniques to propagate Prosopis so that large portions of arid and semi-arid tracts could become covered in a short period. The project also contains a training component where one veterinary science graduate will be trained at the master's degree level while two others will study plant ecology and plant establishment in arid habitats. The three graduates will later be appointed as research workers in the Arid Zone Research Division so as to strengthen the term working on arid lands problems.
Research, training, adequate funds and facilities, and extension are prerequisites for effective arid lands management. Research is needed to identify the cheapest and most practical methods of maintaining the soil in its most productive state. Training is required for furnishing research with the type of skills that can cope with the problems involved. A good part of this training needs to be undertaken on the site of such problem areas. Classroom courses can give trainees a broad view of all environmental factors, their interactions, and how they affect the resource as well as the socioeconomic life of the inhabitants.
It seems inappropriate to give here a list of all the subjects to be covered but it might be beneficial to list some of the most relevant and important ones. They include resource mapping; ecological studies, especially of the tolerance of plants to drought and salinity; phytodynamic studies covering areas such as intensity of grazing and effect of fires; crop rotations; mechanized farming methods; proportion of annual to perennial Graminae; ability of leguminous species to regenerate; and characteristics of various types of vegetation in relation to fodder production and soil protection (Dixey and Aubert, 1962).
Studies should further concentrate on integrated resourceuse with respect to crops, pastures, forests, wildlife, soil, and water. On the social side there is a need for courses on nomadism, animal migration routes and size of herds, and farming methods. Biochemical studies on the nutritive value of the main native fodder plants and of introduced plants are required. Such studies may include plant exudates (gums, resins), tannins, and other extracts.
The necessity for adequate funds for research work does not need elaboration. It is unfortunate that the majority of those who approve budgets are graduates in the humanities and are not conversant with the needs and benefits of scientific research.
In these problem areas, the most urgent requirements are means of transportation and accommodation. In addition to problems of funds for equipment, there is also the difficulty of getting the wanted items at the right time. Both foreign exchange problems and lengthy routine procedures add to other difficulties encountered.
Benefits of Successful Techniques to Other Countries
Techniques that prove to be successful in the Sudan will no doubt be of use elsewhere. The Sahelian countries, for example, are experiencing largely the same problems of land degradation. Many of these areas have similar climate and biological circumstances with respect to over-cutting, overgrazing and over-cropping. Therefore, any conservation measures found successful in the Sudan can be adopted by these countries without loss of time or extra expenditure on research. Economic crops introduced and found successful in the Sudan can be introduced in these countries without going into elimination trials. The Sudan can also become a source of seeds for such crops needed for conservation or production.
Dixey, F., and G. Aubert. 1962. "Arid Zone Research in the Sudan."
Arid Zone, No. 16 (June 1962), pp. 5-16. Unesco, Paris.
Musnad, H.A. 1970. "Forests as a Means of Utilising Marginal Lands in the Sudan." Paper read at the First Conference of Arab Agriculturalists.
-.1971. "Soil Moisture Conservation for Plant Growth in the Arid Climate of Northern Sudan." M.Sc. thesis, University of Khartoum.
-.1975. "Soil Conservation and Land Use in the Sudan." Sudan Silva, 3, pp. 34-38.
-.1977. "Land Reclamation in Kerma Basin." Sudan Silva, 3, pp. 69-78