Category: Slope gentle

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Stone Lines

Similar names: Cordons pierreux, stone bunds.

Stone lines are stones grouped in the shape of a line and placed along contours. The stones can be of different sizes. The goal of these lines is to conserve the soil and reduce runoff, as they are used to slow down water runoff and break its velocity. Hence, they increase infiltration and retain sediment and seeds to make water and nutrients available for crops. Stone lines are most suitable for water harvesting on slightly sloping plains (up to 5%) in semi-arid regions. For slopes starting from 5%, stone bunds can be used (see eyebrow terraces).

Stone lines are an easy and cheap intervention if stones are available in the immediate surroundings. This intervention is widely used in Africa, both in dry and humid areas. Moreover, stone lines are often used in combination with Zai Pits intervention for the rehabilitation of degraded and crusted lands. It is applied in semi-arid areas, on sandy and loamy soils where the slope is lower than 5%. A great example can be seen in Niger, where the combination of the two techniques is applied to capture runoff, making infiltration more efficient and improving nutrient availability. The pits have a diameter of 20-30 cm, and a depth of 20-25 cm and are spaced about 1 m apart in each direction. Stone lines are spaced 20-25 m apart on slopes of 2-5%. With this layout stone lines are quite small, usually, three stones wide and only one stone high and they are placed, along the contour lines, by hand. Very often grass grows between the stones leading to a greater infiltration and helping the accumulation of fertile sediments. Maintenance-wise, stone lines need to be repaired annually, in particular after heavy precipitation events.

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Terracing

Terracing is a method of farming and soil conservation on hills and sloped lands. It was traditionally used by the Incas and is widely practised around the world today. It involves the building of platforms, and forming step-like structures along a slope. The main goal of bench terraces is to periodically interrupt the slope of the terrain with flat sections; this helps to decrease the speed of water runoff,  significantly reducing soil erosion and surface runoff. By slowing down water speed, this intervention stops the washing away of topsoil containing important nutrients and promotes better water infiltration and soil moisture. The flat benches of the terraces create more effective and productive areas to farm on steep terrain.

There are two main types of terracing techniques: graded terracing and level terracing. With graded terracing, the slope can vary along the length of the terrace to direct water in the desired direction; this is especially useful for less permeable land. With level terracing, the terraces follow a contour line and do not vary in slope along this line, this ensures that water is more evenly distributed along the terrace. Stone or wooden walls are often used to hold terraces in place, although a simple earth wall without supporting material can be used with slopes and terraces on the smaller side. This intervention is similar to Fanya Juu and Fanya Chini which are specific types of terraces.

Terracing offers several ecological and socioeconomic benefits. Ecologically, it prevents soil erosion by slowing water flow, allowing it to infiltrate the soil and retain valuable topsoil, which is essential for agriculture. Terracing also manages water more effectively by evenly distributing it across levels, conserving water, reducing irrigation needs, and promoting nutrient cycling. It creates diverse habitats for various plant and animal species, enhancing biodiversity. Additionally, terracing stabilizes slopes, reducing the risk of landslides by minimizing soil pressure and movement, especially in regions with wet seasons. Socioeconomically, terracing increases land productivity on slopes, allowing for larger crop beds and easier use of machinery, thus boosting agricultural efficiency.

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Vegetative Lines

Vegetative lines involve the planting of lines of vetiver grass following the contour lines, along stream banks and roadsides, to create a hedge. These hedges act like semi-permeable barriers, aimed to hinder surface erosion as they slow down run-off and retain sediments picked up by excess rainwater. This setup improves water infiltration and helps to increase the ground moisture level. Their root systems also help stabilise the soil and prevent further soil erosion. Thus this provides increased stabilisation of embankments, gully erosion, roads and slopes. Furthermore, water runoff and soil runoff reductions are observed, at around 57% and 80% respectively.

Vetiver grass can grow on slopes of > 50% and can be planted on a high variety of soils (red latosols, black cracking vertisols, roadside rubble, C-horizon gravels, laterites, sodic, and saline soils). Furthermore, vetiver grass is resistant to different types of climatic conditions: rainfall from 600mm to 6000 mm /year and extreme temperatures of -14°C to 55°C, and could survive several months submerged in water. Vetiver grass can support high levels of toxicity by manganese, aluminium and other metals and high levels of soil acidity, salinity, alkalinity, and acid sulphate conditions. All in all, they provide great solutions as they are non-invasive, fire resistant, and regrow quickly and be used as mulch, fuel (vetiver energy value is 55% the energy value of coal), and as fodder. Finally, vetiver grass is very efficient in stabilising Semi-Circular Bunds, Eyebrow Terraces or Negarim.

Very similar to the intervention described above is the so-called “Vegetative lines with cactus”. This intervention is based on the same principle as the Vegetative lines with vetiver grass, but it is suitable for drier environmental conditions (0 – 600mm). Like some other interventions, over time, this type of intervention can lead to the formation of terraces due to tillage and water erosion between the hedges.

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Negarim

Similar names: diamond-shaped micro catchment, V-shaped micro catchment, V-shaped bunds, Triangular bunds, small run-off basins

Negarim is an intervention that consists of small runoff micro basins characterised by a diamond shape, bound by low earth bundles. This water harvesting technique is mainly used for growing trees and bushes in arid and semi-arid areas but, as a side effect, it also preserves soil from erosion. It works great with rainfall rates starting from 150 mm/y and can be applied on slopes of up to 15%. This technique is more suitable for small-scale tree-planted areas and is pretty easy to create. Since Negarim mostly targets tree- and bush-planting, the area in which this technique is performed should be characterised by a soil depth of at least 1.5 metres, but preferably 2m. This is to ensure enough space for the roots to develop and for adequate storage of the water harvested.

The technique was originally developed in the Negev desert in Israel; in fact, the word Negarim comes from “Neger”, the Hebrew word for runoff. Nonetheless, the first report of this water harvesting technique comes from the south of Tunisia. This microcatchment system is widely spread in Israel, especially among research farms in the Negev desert where the yearly amount of rainfall reaches 100-150 mm. However, Negarim and its variations are well known, and used also, in other arid and semi-arid areas like in North- and Sub-Saharan Africa.

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Fanya Chini

Similar names: Retention trenches, infiltration trenches

The name Fanya chini means “throw it downwards” in Kiswahili. It consists of trenches and earthen ridges facing downslope. This intervention aims to reduce soil erosion by breaking down long slopes into smaller sections. Thus, the speed of runoff will decrease, and water can infiltrate into the soil between the bunds. This will result in a reduction of nutrient leaching and increased water availability for crops. Fanya chini is common in areas with 300-600 mm of annual rainfall on 1-25% slopes. It is suitable for all types of relatively permeable soils (e.g. alluvial, red, laterite, brown, and shallow and medium black soil). Still, it doesn’t work very well with clayey soils or vertisols as these are not permeable.

One of the main benefits of Fanya chini is that it limits soil erosion from water runoff, and simultaneously improves water retention in the soil and increases water availability for crops. Furthermore, an increase in yield is observed, as well as improved soil fertility.

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Fanya Juu

Similar names: Terracing, Retention Trenches, Infiltration Trenches

The Fanya Juu technique is an agricultural practice that involves creating ridges along the contour lines of sloping land. The name Fanya Juu means “throw it upwards” in Kiswahili and is very similar to Fanya Chini as it consists of terrace bunds and ditches along the contour. This technique rapidly spread during the 1970s and 1980s and it is well known throughout Eastern Africa, the goal of Fanja Juu contour bunds is different depending on the environmental conditions of the areas within which they are applied. Their aim in semi-arid areas is to harvest and conserve rainfall, whereas, in sub-humid zones, contour bunds are constructed to discharge excess runoff. However, their main purpose is to prevent water and soil loss and to make conditions more suitable for plants to grow. 

Fanya Juu is suitable for slopes of 5-20%, similar to the ones that characterize Fanya Chini interventions. The species most often used in drier zones are Pennisetum Purpureum (Napier grass or Uganda grass) and Panicum Coloratum (also known in southern Africa as “white buffalograss”) and the harvest can be used as fodder for livestock. Fruit trees (e.g. citrus or bananas) can be planted either immediately above the embankment or below the ditch, where runoff tends to concentrate.

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Eyebrow Terraces

Similar names: Banquettes, Boomerangs, Terraces, Stone Bunds, Eyebrow Systems, Eyebrow Basins.

Eyebrow Terraces are a form of microcatchment water harvesting system. They are handmade micro basins, in the shape of an eyebrow, and are often made from soil and stones. Their main goal is to facilitate vegetation growth on steep slopes by collecting runoff water from a small catchment area and having it infiltrate the soil. This way, it is stored in the root zone and will be available for crops. They are usually situated on hillsides and can be used on up to 50% of slopes. The steeper the slope, the more the bunds have to be reinforced with stones. Eyebrow Terraces work well in areas characterised by 200-600 mm of annual rainfall. Reinforcing Eyebrow Terraces with stones on steep slopes makes them more resistant to the increased water speed caused by the slope. Instead, they can be some metres apart. After completion, the pit uphill from the eyebrow may fill with sediments and soil, thereby giving rise to terraces.

Some of the main advantages of Eyebrow Terraces are that they reduce the risk of flooding, while simultaneously increasing the on-site conversion of water through the facilitation of filtration. Furthermore, the intervention improves the yields in the area, by increasing the soil organic content, as sediments are trapped in the terraces.

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Exclosures & Enclosures

Enclosures are fencing structures that restrict animal and human access to land with the goal of supporting the regeneration or protection of said land. Enclosures also refer to the practice of fencing-off an area in order to protect it from human use and animal intrusion. The main goal of Enclosures through fencing is to allow natural regeneration and rehabilitation of degraded lands within the enclosed space. This intervention fosters natural regeneration and helps to restore organic matter and a healthy soil structure. Enclosures can also be used to change the cover of the land to allow time for new land coverage (vegetation) to be established. Enclosures can be applied in a variety of different landscapes and environmental conditions. This technique is a relatively cheap intervention if the materials are available on site but can be somewhat more expensive where materials need to be acquired or where more sophisticated Enclosures are built. Fencing could be done for a permanent or temporary use, and this is defined by the goal of the project. 

Some of the major features of Exclosures and Enclosures are the economic benefits linked to the environmental benefits coming as a result of their implementation. Firstly, the increased vegetation that comes as a result of fencing increases vegetation which in return enhances water-retention capacity of soil. This helps to both replenish the nutrients in the soil and to restore the ability of the soil to retain water.  Furthermore, the enhanced water retention capacity of the soil reduces the exposure to flood damage. When it comes to agriculture, Enclosures and Exclosures improve long-term returns from crop production and pastureland, as the long-term productivity of the land is improved by improved and regenerated soils. This helps to increase crop yields quality. Exclosures and Enclosures can increase security of land tenure and make property rights clearer due to clear demarcations of the boundaries of your land. This can, in turn result in a higher willingness to invest in the land. Finally, Enclosures and Exclosures provide an opportunity for complimentary economic activities to be realised, such as harvesting grass (‘cut and carry’), extraction of wood, or growing of fruits and vegetables. Growing additional crops can also increase and diversify income streams and contribute to enhanced food security.

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Grazing Management

Sustainable Grazing Management is about managing pasture and livestock in a way that prioritizes the long-term capability of a landscape. Its goal is to maintain healthy and productive pasturelands and provide economic benefits, and can be applied to range, pasture, and grasslands in all types of topographies and climates. The way grasslands are managed both directly and indirectly impacts the ecological health of the surrounding ecosystem, including the local water and mineral cycles as well as biological succession, in turn also creating socioeconomic effects for farmers and herders.

As opposed to more traditional and unsustainable practices such as extensive or continuous grazing where livestock graze on one large, open pastureland, there are several methods of more sustainable Grazing Management. Two examples of this are Rotational Grazing Management and Integrated crop-livestock grazing.

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Farmer Managed Natural Regeneration

Natural regeneration is a biological process that can be assisted and managed by farmers and landowners to increase the recovery of native ecosystems and their functions. Usually practised on wooded agricultural land, Farmer Managed Natural Regeneration (FMNR) is an approach that aims to increase the number of trees by protecting, managing and pruning existing tree and shrub stumps and roots to create the optimal conditions for them to flourish and germinate seeds again. 

An advantage of FMNR is the freedom that farmers have in implementing and adapting this technique to their specific landscape. Farmers can make decisions based on their knowledge and experience and choose which tree species they want to target, for example, fruit trees. Farmers can also select which species they want to save or remove during the pruning process, as well as when and what preferred tree density they want.