The plateau is an area of about 10,000 km2, 10-15% of which is arable. Ironically, the areas with the least arable land, which can be 2-3% arable, are the most populous. Rainfall averaged 465 mm yearly between 1969-1989. Soils are generally skeletal with hardpans limiting percolation. The rains dig gullies, leaving large ravines in the dry season.
To get the most out of their land, the Dogon people have developed two modes of cultivation: field crops in the rainy season and market gardening in the dry season. Both methods depend on simple local technologies to ensure production.
Mounds. The most common soil conservation practice is moundmaking, or the technique of building small cone-shaped piles of dirt and weeds. Mounds are spaced between the sorghum and millet plants, and vary in size depending on soil type and the mound maker. The average size is 35 cm high and 60 cm wide. Mounds slow down runoff, facilitate percolation and aeration, and provide seedlings with a physical barrier against the elements. They also function as mini compost heaps where succeeding crops can be planted.
Terraces. For steeper slopes, low stone terraces are constructed along the contours, crisscrossed by secondary terraces to form squares or pockets. After the land inside is leveled, the pockets retain rainwater and soil, allowing percolation.
Stone Lines. Stone lines are arrangements of unconnected stones in a line perpendicular to runoff. Sometimes intersecting lines are used to increase their effectiveness. Stone lines are widely used, generally on mild slopes. They slow the flow of water, trap vegetative debris, and permit percolation. This method is also used to recover severely eroded areas. However, if the stones are not firmly well-placed, they can be washed out, creating a channel for gullying.
Bunds or Low Stone Walls. Bunds are thicker and more substantial than stone lines. They are used to reclaim gullies, and can be found sporadically throughout the plateau. Crops above the walls can tolerate drought and grow better. One drawback is that weeds grow in abundance next to the wall and must be removed.
Square Basins. Watertight furrows are constructed in a checkerboard pattern to form individual basins on soils that do not percolate well. The main ridges of the basins are generally long, running downslope with about 1.5 to 3m between them. Spacing between the furrows is a function of slope. Basins work best on gentle slopes with less porous and relatively deep soils, as they are 40-100 cm deep. The watertight basins hold rainfall and eliminate erosion, increasing yields up to 25-30%. However, heavy downpours and regular field maintenance can damage the basins. Although basins are increasing in popularity, the extension of the market garden calendar has reduced the time available for their construction.
Planting Holes. There are two kinds of planting holes: a shallow hole or a larger water catchment into which seeds are sown. The larger planting holes are roughly 20 cm in diameter and 15-20cm deep, constructed on a line about 30-35cm apart, and used on relatively deep and hard-to-work soils. Planting holes limit runoff and retain ground water. This technique is decreasing in popularity as more time is given to market gardening and less to field crops.
In addition to the above techniques, crop residues are also exploited. Stalks are arranged in bands on the fields, or scattered about. They trap vegetative matter, reduce evapotranspiration, and decompose quickly into available nutrients.
Mounds, planting holes, basins, stone lines, and terraces are often complementary and can be found in the same areas, sometimes in the same field. The oldest techniques are mounds, hill terracing, and stone lines. These techniques are applied to specific soil conditions within the plateau. All techniques help to increase yields, in particular, basins and planting holes. In years of high rainfall, the Dogon concentrate on reclaiming skeletal lands. In times of low rainfall, these techniques are used to protect and maintain production yields.
Vegetable cultivation. Vegetable or market gardening provides an extra source of income. Production includes onions, tomatoes, sweet potatoes, tobacco, eggplant, and peppers. Onion is the major garden cash crop. Onion production is increasing annually because more land is being planted. Last year over 23,000 tons were produced. In comparison the next largest crop was tomato, which yielded only 3,900 tons. Garden sites often have no soil. The Dogon carry soil to these rocky sites, then hold it in place with rock terraces, similar to those mentioned above. Rock walls are built in squares or pockets of about 1 - 2 m2, close to a water source. Building and filling the pockets is a labor-intensive process that involves the following:
During the rainy season the gardens are used for field crops. Although the popularity of vegetable gardening has somewhat reduced the time available for preparing field crops, production seems unaffected.
Despite all the adversity, the Dogon survive. Every year more fields are abandoned to erosion, leaving only hardpan soil. But the Dogon have reclaimed land that otherwise would have been lost to desertification, and there is still room for technical improvement. For example, low stone walls could be improved by setting more accurate contour lines, by slightly burying the first layer of stone to create a stronger foundation, and by filling gaps in the wall to reduce channeled water flow.
Perhaps by improving traditional techniques and introducing new ones, there is still potential for reclamation of the Dogon Plateau.
Roberts, D. (1990). MaliÕs Dogon People. National Geographic, 178(4), p. 100.
Dr. Camilla Toulmin, Director
Dryland Networks Programme
3 Endsleigh Street
London WCIII ODD England