An advanced agricultural technology is helping farmers in Uganda’s Southwestern Highland Agricultural Zone achieve unprecedented crop yields while fighting the devastating effects of soil erosion and climate change. The innovation, known as “contour reversed bench terraces,” is a collaborative effort led by research scientist Amos Rutayomba of the National Agricultural Research Organisation (Naro).
Food basket
The highland agro-ecological zones of Uganda are vital to the agricultural sector. Characterised by mountainous terrain, elevated plateaus and fertile volcanic soils, these regions provide a unique environment for cultivating a diverse range of crops that are critical for both food security and economic activity.
The cooler temperatures and reliable bimodal rainfall pattern support the growth of various crops, including cash crops such as tea and coffee, as well as essential food crops such as bananas, beans, Irish potatoes, vegetables and cereals. The favourable climate and soil conditions allow for intensive farming practices, though challenges such as soil erosion remain a concern.
Within the Southwestern Highlands, the Kigezi sub-region, which includes Kabale, Rubanda and Kisoro, is widely recognised as a major hub for Irish potato production in Uganda. The region’s cool, temperate climate and rich soils are exceptionally well-suited for growing Irish potatoes. Kigezi contributes a substantial portion of the country’s Irish potato output. The Irish potato is a key food security crop and a source of income for many farmers in the area due to increased urbanisation. However, a decline in production poses great risks.
The contour reversed bench terraces technology offers a lifeline to communities in the Kigezi Highlands, a region plagued by fragile and highly degraded agricultural land. For years, the area has suffered from severe erosion, with deep gullies scarring the landscape. Farming has been dominated by annual crops with little to no perennial crops, agroforestry, or dedicated grazing areas. The land is highly fragmented, hardly fallowed and suffers from very low productivity, making it a difficult environment for farmers to thrive.
An advanced approach
Rutayomba, a system agronomist at Kachwekano Zonal Agricultural Research and Development Institute (KaZARDI), explains that the technology is an advanced integration of traditional soil and water conservation methods. Unlike older terracing techniques that simply create a flat surface on a slope, this new approach ‘benches on the contour lines and reverses the gradient to have a flow back.’ This unique reversal, he says, is key to its success. ‘With this technology, we harness all the runoff downwards. Any water on a particular point in the landscape is held from where it has been received from the rain,’ Rutayomba says.
The method works by creating a series of flat, bench-like structures on hillsides that follow the natural contour of the land. These bands are hinged at a 45-degree angle, which reduces water flow. Excess water is captured in strategically placed contour water retention trenches and check dams, preventing it from washing away the nutrient-rich topsoil. The project, initially developed under the Eureka Project Fund in 2022, also incorporates specialised grasses like napier and vetiver, which form a strong root network to hold soil in place. Additionally, leguminous trees such as calliandra and vernonia are planted to stabilise the terraces, capture atmospheric nitrogen, and bring phosphorus back into the soil for crops to use.
Benefits
The restored landscapes with bench terraces come with short, mid-term, and long-term benefits that can be realised even on half-acre plots. These include increased water use efficiency, a reduction in the number of dry days and the creation of a resilient landscape. The technology supports diversified cropping systems and reduces pressure on fragile ecosystems, including wetlands, which are often over-cultivated. It also enables an integrated zero-grazing livestock system, making it a basis for socio-economic transformation in the region.
Financial returns
A cost-benefit analysis for a typical half-acre plot shows a strong return on investment. The major costs include a one-time establishment fee for properly stabilised bench terraces at Shs4m. Annual farm operational costs for potatoes (seed, disease management, and labour) are estimated at Shs3m, while a dairy cow requires Shs1.5m for veterinary services and labour. This brings the total first-year cost to Shs8.5m. In return, the benefits are significant.
Potato production can yield up to 40 bags per season, bringing in Shs12m over two seasons. The sale of milk from a dairy cow can add another Shs3m (3,000 litres at Shs1,000 per litre), totalling an annual benefit of Shs15m. Since the terrace construction is a one-off cost, the financial benefits will only increase in subsequent years, providing sustainable, gainful employment and supporting the socio-economic transformation of Kigezi’s communities.
Community adoption
The technology is now being brought to communities through the BRIGHT (Building Resilience and Inclusive Growth for Highland Farming Systems for Rural Transformation) project, funded by the Netherlands Ministry of Foreign Affairs and implemented by International Fund for Agriculture Development (IFAD) .
Rutayomba notes that the community’s “body language” and willingness to adopt the practice are clear indicators of its immense potential.
‘They are already willing to adopt and implement and expand it on a grand scale,’ he says, expressing optimism about the future of farming in the region.
Advantages of terracing
As one of the oldest techniques for conserving water and soil, terracing is common in hilly and mountainous regions that are subjected to substantial population pressure. Terraces are built along contour lines to increase the arable surface area and conserve water and soil on hillslopes. Terraced fields can be of different shapes and sizes, and consist of a flat section and a near-vertical riser, protected by a wall of dry stones, soil, grass, or trees. The height of the riser or wall can be from several decimetres to a few meters, with a continuous or intermittent structure comprised of single walls or a complex series of walls.
Reduced runoff, water conservation
There are three primary ways that terracing reduces runoff and sediment loss. First, terracing transforms steep slopes into an artificial sequence of relatively flat surfaces, thereby decreasing slope length and gradient, which significantly reduces sediment yield and runoff. Second, terracing increases surface roughness and vertical surface relief.
This increases infiltration, soil moisture, and the soil water holding capacity. Terracing can increase soil moisture content by 4.24 percent-12.9 percent (5.0-6.2 times that of sloped land) and also found that terraces can store water and thereby, allows for the restoration of vegetation in water-limited ecosystems.
Third, terracing often includes the formation of ridges or embankments that were greatly beneficial in reducing runoff. Terraces with ridges, for example, have been shown to retain 18 percent more runoff than terraces without ridges.
Erosion control, soil conservation
Soil erosion is closely related to runoff. During intense storms, a portion of the rain infiltrates into the soil and the remainder becomes runoff. As runoff increases, its velocity, volume and erosivity also increase. In addition, the terraces intercept not only the water and sediment they produced, but also the sediment-laden flow coming from the upslope. The effect of soil erosion control is especially significant when considering the effects of sediment reduction in terraced surface, the interception of upslope runoff, and the reduction of downhill gully sediment yield by reducing slope runoff.
Increase in crop yield
The recent global increase in terracing relates to increased population density in areas with limited arable land. By terrace building, a steep slope is converted into a relatively flat surface that not only increases the area available for cultivation but also facilitates more intensive farming practices. In general, arable land can be increased by 20 percent -40 percent through the conversion of slope land into terraced fields, which significantly increases grain yield (about 20 percent -40 percent).
Besides, farming practices, such as ploughing, help to form pedo-environments with their own characteristics, i.e., modified profiles with high percentages of organic materials and nutrients. That is why terraced soils usually have higher organic matter and nutrient contents compared with non-terraced agricultural plots. Furthermore, terracing also increases the moisture by avoiding water loss, which effectively enhances crop endurance to droughts and consequently increases crop yield. Accordingly, terrace is especially important for the irrigation and fertilisation of barren hillsides.
Cultural landscape
Terracing creates a cultural landscape that reflects human wisdom in understanding the relationship between man and a specific environment, as well as the connection with a valuable natural ecosystem. Over the past decades, there has been an increase in research on terraced landscapes within the fields of geography, landscape architecture, ethnology, rural sociology, and other spatial disciplines. Terraces have been identified as part of a ‘cultural landscape’ heritage and play a key role in aesthetic appreciation and spiritual enrichment.
Famous examples are the Arab gardens in Spain and the agricultural terraces in Central and South America and Asia. These terraces attract thousands of visitors each year due to their aesthetic value and productive, pleasing, neat, and sustainable landscapes. Thus, terraces create large income for local residents). At the Longji terraces in China, for example, income from tourism accounts for 70.8percent of the total income for local families. Across the globe, five well-known ancient terraced fields have been designated as globally important agricultural heritage systems (GIAHS) by the Food and Agriculture Organization (FAO) of the United Nations.
Tip
The contour reversed bench terraces technology offers a lifeline to communities in the Kigezi Highlands, a region plagued by fragile and highly degraded agricultural land. For years, the area has suffered from severe erosion, with deep gullies scarring the landscape. Farming has been dominated by annual crops with little to no perennial crops, agroforestry, or dedicated grazing areas. The land is highly fragmented, hardly fallowed and suffers from very low productivity, making it a difficult environment for farmers to thrive.