Sani Mamadou Abdou
Programme d’Appui à l’agriculture Productive (PROMAP), Niamey, Niger
有助于对技术进行记录/评估的项目名称（如相关）Good Practices in Soil and Water Conservation - A contribution to adaptation and farmers ́ resilience towards climate change in the Sahel (GIZ)
有助于对技术进行记录/评估的机构名称（如相关）Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) - 德国
Semi-circular bunds are used to rehabilitate degraded, denuded and hardened land for crop growing, grazing or forestry.
This technique involves building low embankments with compacted earth or stones in the form of a semi-circle with the opening perpendicular to the flow of water and arranged in staggered rows. They are constructed on gently to moderately sloping pediments and plateau areas in order to rehabilitate areas that are degraded, denuded and/or affected by soil crusting.
Depending on their purpose, the areas inside the semi-circular bunds, enriched with organic fertiliser, are used for growing cereals (crop crescents) and for planting trees, bushes and/or grasses (forestry and pastoral crescents). Semi-circular bunds slow down and capture runoff, providing the plants inside them with the water they need. They therefore reduce the loss of water and the fertile layers of the soil. This is particularly advantageous when rain is scarce, as the semi-circular bunds channel water towards the plants, increasing the moisture available to them. In the medium term, rich sediment builds up behind the semi-circular bunds, which helps to protect and restore the land. The bunds ensure that the manure placed around the plants inside them is not washed away by heavy rains, and the ridge of the bund protects young plants from the wind and wind erosion. When they are used for reforestation, they increase the rate of survival of the trees planted in them. Cropland bunds enable crops to survive dry spells. Earthen bunds are not, however, suitable in a scenario with heavy rainfall. They do not allow water to filter through, which can result in the soil inside them becoming waterlogged and the plants being flooded. This can lower yields in the case of crops that do not tolerate excess water. In such conditions, stone bunds are preferable.
To establish semi-circular bunds on cropland, the following activities are required: marking out the contour line, laying out the lines of the semi-circular bunds in staggered rows, digging the microcatchment, forming the ridge downhill of the microcatchment, applying organic fertiliser (around 1 t per ha per year).
To establish semi-circular bunds on forestland the same steps are required, however instead of applying fertilizer, other steps include digging the holes, planting the trees, and sowing grass on the ridges. The earthen ridges around cropland bunds need to be rebuilt each year. It is recommended that the ridges of forest/rangeland bunds be maintained each year and raised if overflowing has occurred. Forest/rangeland sites should be protected from grazing animals in the first two to three years, until the vegetation is well established. This requires good community organisation. After dry years, forest/rangeland semi-circular bunds may have to be re-sown with grasses and replanted with trees.
The Sahel is a region where the population has always faced a high degree of climate variability, manifested both in terms of time (unexpected dry spells can occur during the rainy season) and in terms of space (rainfall can vary greatly from one area to another). The population is mainly composed of small farmers and livestock keepers.
Over the last two decades, the effects of climate change have exacerbated the already difficult conditions. Accord¬ing to projections made by climatologists, the Sahel will experience a rise in temperatures combined with highly variable rainfall and an increase in extreme weather events. The Soil and Water conservation and rehabilitation techniques have helped people in the Sahel to manage their ecosystems more effectively and improve their productive land. As a result, communities are better prepared to cope with environmental changes (changes in the climate, land degradation, etc.) and the im¬pact of shocks, particularly droughts.
Niger, Burkina Faso, Chad
Regions of Tillabéri, Filingué, Ouallam, Téra and Tahuoa in Niger; Bam region in Burkina Faso
- 10-100 平方千米
Also implemented in Burkina Faso and Chad
Regions of Tillabéri, Filingué, Ouallam, Téra and Tahuoa in Niger; Bam region in Burkina Faso
developed, implemented and disseminated as part of projects and programmes undertaken from the 1980s onwards to combat desertification and improve natural resource management. Implemented by GIZ (German Federal Enterprise for International Cooperation), PDRT (Projet de développement rural de Tahoua - Tahoua Rural Development Project), PASP (Projet de protection intégrée des ressources agro-sylvo-pastorales Tillabéri-Nord - Project for the Integrated Protection of Agricultural, Forest and Rangeland Resources in Tillabéri-Nord)
Longest growing period in days: 120, Longest growing period from month to month: August to October
Major land use problems (compiler’s opinion): droughts, soil erosion, lack of water, surface runoff, soil crusting, unadapted land use methods, rapidly growing population increasing pressure on land, reduced or abandoned fallow periods, soil erosion, insecure access to land.
Cut-and-carry/ zero grazing, Improved pasture, agropastolralism
Livestock density: 1-10 LU /km2
Main causes of degradation: soil management (Unadapted landuse methods, reduced or abandoned fallow periods), crop management (annual, perennial, tree/shrub) (Neglect of fallow periods and crop rotation), droughts (due to heat waves), population pressure (rapidly growing population, increasing pressure on land), land tenure (insecure access to land and collectively managed community land), poverty / wealth (very poor population)
Secondary causes of degradation: deforestation / removal of natural vegetation (incl. forest fires) (deforestation through overgrazing and fire wood collection), over-exploitation of vegetation for domestic use (firewood collection), overgrazing (cattle, sheep and goats), change in temperature (Climate change: heat waves), change of seasonal rainfall (more variable onset of rain), Heavy / extreme rainfall (intensity/amounts) (more variable and intensive rains), wind storms / dust storms (frequent storms), floods (due to intensive rain storms), labour availability (some migration of men to nearby cities), education, access to knowledge and support services (high level of illiteracy)
Source: Ministère du Développement Agricole Niger (without date): Recueil des fiches techniques en gestion des ressources naturelles et de productions agro-sylvo-pastorales.
Technical knowledge required for field staff / advisors: moderate
Technical knowledge required for land users: low
Main technical functions: control of dispersed runoff: retain / trap, control of dispersed runoff: impede / retard, control of concentrated runoff: retain / trap, control of concentrated runoff: impede / retard, increase of infiltration, increase / maintain water stored in soil, water harvesting / increase water supply, sediment retention / trapping, sediment harvesting
Secondary technical functions: improvement of surface structure (crusting, sealing), stabilisation of soil (eg by tree roots against land slides), increase in nutrient availability (supply, recycling,…), reduction in wind speed
Bund/ bank: semi-circular/V shaped trapezoidal
Depth of ditches/pits/dams (m): 0,15-0,20
Width of ditches/pits/dams (m): 2
Length of ditches/pits/dams (m): 4
|1.||marking out the contour line|
|2.||laying out the lines of the semi-circular bunds in stag- gered rows|
|3.||digging the microcatchment|
|4.||forming the ridge downhill of the microcatchment|
|5.||applying organic fertiliser (around 1 t per ha per year) (only on cropland, this step is not required on forestland)|
|6.||digging the holes (only on forestland)|
|7.||planting the trees (only on forestland)|
|8.||sowing grass on the ridges (only on forestland)|
|1.||The earthen ridges around cropland bunds need to be rebuilt each year||each year|
|2.||the ridges of forest/rangeland bunds be maintained each year and raised if overflowing has occurred.||each year|
|3.||After dry years, forest/rangeland semi-circular bunds may have to be re-sown with grasses and replanted with trees.||after dry years|
|4.||Forest/rangeland sites should be protected from grazing animals in the first two to three years, until the vegetation is well established.||in the first two to three years|
other costs for cropland semi-circular bunds: 10 cartloads of manure.
other costs for forestland semi-circular bunds:
• 625 tree seedlings
• 15 kg of grass seed
• cost of transporting 625 tree seedlings (2 cartloads)
• 120 seedlings to replace trees that die.
In the case of forest/rangeland semi-circular bunds, the availability of tree and grass seeds and seedlings is a vital factor. In the PDRT and PASP projects in Niger, the villages had nurseries, and members of the village land manage- ment committees collected grass seeds from rangelands to sow in the semi-circular bunds.
- < 250毫米
- > 4,000毫米
Thermal climate class: subtropics
- 0-100 m a.s.l.
- 101-500 m a.s.l.
- 501-1,000 m a.s.l.
- 1,001-1,500 m a.s.l.
- 1,501-2,000 m a.s.l.
- 2,001-2,500 m a.s.l.
- 2,501-3,000 m a.s.l.
- 3,001-4,000 m a.s.l.
- > 4,000 m a.s.l.
- 非常深（> 120厘米）
Population density: 10-50 persons/km2
Annual population growth: 3% - 4% (mostly poor households below poverty line).
Off-farm income specification: men migrate temporarily or permanently to cities for off-farm income, women and men seaonally carry out paid farm labour
- < 0.5 公顷
- 0.5-1 公顷
- 1-2 公顷
- > 10,000公顷
traditional land use rights are prevailing. On fields individual land use rights, communal rights on pasture and forest land (collection of wood and other products (fruits, medicinal plants))
Cropland bunds constructed on abandoned farmland increase millet yields by 180 kg and straw yields by 400 kg per hectare per year
Forest/rangeland sites should be protected from grazing animals in the first two to three years, until the vegetation is well established. This requires good community organisation.
Sites improved with semi-circular bunds for reforestation produce one stere of wood per hectare per year after ten years. The value of this production can increase further from the fifth year onwards to around 850,000 CFA francs per hectare
contribution to human well-being
notably increses production of food, fodder and forest products
survival of planted trees
Physical structures can be biologically stabilized through planting of grass, bushes or trees. Damages are generally small but need to be repaired quickly.
Forest/rangeland sites should be protected from grazing animals in the first two to three years, until the vegetation is well established. Semi-circular bunds on forest/rangeland can achieve a remarkable regreening of the environment and promote biodiversity. Cropland bunds constructed on abandoned farmland increase millet yields by 180 kg and straw yields by 400 kg per hectare per year. Sites improved with semi-circular bunds for reforestation produce one stere of wood per hectare per year after ten years. The value of this production can increase further from the fifth year onwards to around 850,000 CFA francs per hectare.
- > 50%
60% of land user families have adopted the Technology with external material support
The techniques were implemented with food for work in the 1990s to 2000. Between 2000 and 2012 the work provided by land users was not compensated. Only small equipment and transportation were provided for free.
40% of land user families have adopted the Technology without any external material support. Some adoption (without support by the project) has been observed in some places. The level of replication is however limited to locations where stones are available nearby. Otherwise transportation becomes a problem.
There is a little trend towards spontaneous adoption of the Technology. Semi-circular bunds are applied for example in Niger, Burkina Faso, and Chad.
Some adoption (without support by the project) has been observed in some places. The level of replication is however limited to locations where stones are available nearby. Otherwise transportation becomes a problem.
|Semi-circular bunds slow down runoff and enable the harvested water to be used to good effect. Soil moisture increases and the loss of fertile layers of the soil is reduced.|
|Cropland bunds enable crops to survive dry spells. On abandoned farmland millet yields may increase by 180 kg and straw yields by 400 kg per hectare per year.|
|Semi-circular bunds on forest/rangeland can achieve a remarkable regreening of the environment and promote biodiversity. When they are used for reforestation, they increase the rate of survival of the trees planted in them. Sites improved with semi-circular bunds produce one stere of wood per hectare per year after ten years. The value of this production can increase further from the fifth year onwards to around 850,000 CFA francs per hectare.|
|In the medium term, rich sediment builds up behind the semi-circular bunds, which helps to protect and restore the land.|
|In the event of heavy runoff, a considerable amount of water accumulates inside the semi-circular bunds, and the ridges must be strong enough to withstand its weight. If the water overflows, it can create gaps in the bunds or cut out channels around the sides of them.||The land must be hoed each year.|
|At some sites, rainwater infiltration increases in the first year after the semi-circular bunds have been constructed, but if the land is not hoed, this effect declines considerably in successive years.||In such conditions, stone bunds are preferable.|
|Earthen bunds are not suitable in a scenario with heavy rainfall. They do not allow water to filter through, which can result in the soil inside them becoming waterlogged and the plants being flooded. This can lower yields in the case of crops that do not tolerate excess water (e.g. millet).|
|Animal production may be reduced because forest/rangeland sites should be protected from grazing animals in the first two to three years, until the vegetation is well established.|
Good Practices in Soil and Water Conservation. A contribution to adaptation and farmers´ resilience towards climate change in the Sahel. Published by GIZ in 2012.