Types and Benefits of Bunding in Soil Conservation

In dryland farming, one of the most persistent challenges is keeping water on the land long enough for it to be useful. Rain falls, flows downslope, and carries fertile topsoil with it – leaving behind degraded, moisture-depleted fields. Bunding is one of the oldest and most effective engineering responses to this problem. By constructing small embankments – called bunds – across or along the slope of a field, farmers intercept surface runoff, slow it down, and give it time to soak into the soil. The result is better moisture retention, reduced erosion, and more productive land. This post explains what bunding is, the main types used in practice, and the tangible benefits it delivers for soil conservation.

What is bunding? 🔗

Bunding is an engineering measure of soil conservation that places a physical obstruction in the path of surface runoff to reduce the velocity of water flow. The structures themselves – bunds – are embankment-like constructions that run across the length of a land slope. They can be made from compacted earth, stone, or a combination of both, depending on local soil and material availability. Their core function is simple: by building bunds along contour lines, water runoff is slowed down, which leads to increased water infiltration and enhanced soil moisture. The water that would otherwise run off the field is held back long enough to percolate into the soil profile, where crops can use it.

Bunding is particularly critical in semi-arid and rain-fed farming systems, where there is no supplementary irrigation to fall back on. Farm bunds are useful for both dry and high rainfall regions – in dry regions they hold rainwater in the fields and improve soil moisture, whereas in heavy rainfall areas they hold water and protect from soil erosion. In both situations, farmers benefit from increased crop yield, protection from soil erosion, and improved soil moisture.

Types of bunding 🔗

The type of bund suited to a particular field depends on the amount and distribution of rainfall, soil texture, land slope, and whether the primary goal is moisture conservation or safe disposal of excess water. The type of bund to be built is determined by the rainfall and soil conditions. Below are the main types used across agricultural landscapes.

Contour bunding 🔗

Contour bunds are built along the natural contour lines of a slope – essentially following lines of equal elevation across the field. Contour bunding is an important measure that conserves soil and water in arid and semi-arid areas with high infiltration and permeability, and is commonly adopted on agricultural land up to a slope of about 6%. The job of a contour bund is primarily water conservation – it holds runoff in place and allows it to infiltrate the soil rather than drain away. In locations where yearly rainfall is less than 600 mm and soil moisture is a limiting factor for crop productivity, contour bunds are preferred.

Contour bunds work best in lighter-textured soils such as red soils and sandy loams that can absorb impounded water effectively. They are not recommended for deep black cotton soils, as these soils crack during dry conditions, allowing water to seep through and potentially breach the bund. Contour bunds can save soils from erosion to the extent of 25 to 162 tonnes per hectare annually and are widely practiced in Maharashtra, Gujarat, Tamil Nadu, Karnataka, and Andhra Pradesh.

Graded bunding 🔗

Unlike contour bunds, graded bunds are designed with a slight downward incline – a grade typically between 0.1% and 0.5% – that allows excess water to flow out in a controlled manner rather than pond indefinitely. The graded bund is used in areas having annual rainfall greater than 700 mm, but can also be used in less rainfall areas provided that the soil is of heavy texture. In clay soils where water doesn’t drain quickly, graded bunding is necessary to prevent waterlogging even when annual rainfall is relatively low.

Graded bunds are not suitable on land slopes less than 2% or greater than 8%, and they require a grassed waterway at the outlet point to safely discharge the diverted water without causing new erosion. Graded bunding involves creating graded embankments to prevent soil erosion on flat terrains. Research in western Rajasthan has shown that graded bunding can reduce runoff from 20% to 4.8% and soil loss from 24 to 4.12 tonnes per hectare per year – a dramatic improvement in land stability.

Stone bunding 🔗

Stone bunds use locally available rocks and stones to form the embankment rather than compacted earth. This makes them particularly practical in rocky or stony areas where soil-based bunds may be structurally weak. Contour bunds can be made of stones or soil, and are constructed along a contour in order to best slow the water flowing down the slope, which increases the green water pool of the soil. Stone bunds are durable, require less maintenance than earthen bunds, and improve water infiltration effectively.

Field evidence from semi-arid West Africa supports their value: a study tracking experimental plots in Ghana’s Upper East Region found that stone bunds enhanced soil moisture retention and increased infiltration rates, with intermediate results indicating that stone bunds increased sorghum yields by over 35% compared to control plots. The long-term investment in stone bund construction pays off in both erosion control and crop productivity.

Peripheral bunding 🔗

Peripheral bunds are constructed around the boundary of a field rather than across its slope. These bunds serve as fences and give protection from water and wind erosion in low rainfall areas but are not suitable in heavy rainfall areas. They are useful for flat or gently sloping fields where the primary concern is retaining rainwater within the field boundary and preventing external runoff from entering. Peripheral bunding is straightforward to construct and acts as a first line of defence against moisture loss, particularly for smallholder plots in arid zones.

Compartmental bunding 🔗

Compartmental bunding takes bunding a step further by dividing the entire field into a grid of small, level compartments using a network of cross bunds. Land leveling and compartmental bunding resulted in 15-20% higher yield of finger millet compared to without leveling and bunding. By breaking the field into smaller impounded units, water is distributed more evenly across the entire surface rather than collecting only behind the main bund. This type is especially effective for crops that benefit from even moisture distribution, and is often combined with land leveling to maximise its impact.

Benefits of bunding in soil conservation 🔗

Bunding delivers several interconnected benefits, each addressing a key challenge of dryland and sloped-field agriculture.

Soil moisture conservation 🔗

The most direct benefit of bunding is retaining water in the field. By slowing and impounding runoff, bunds give water time to percolate deep into the soil profile. This extended infiltration period means crops can draw on stored moisture during dry spells between rain events – a critical buffer in regions with erratic or unevenly distributed rainfall. Farm bunding has the potential to bring substantial acreages of dry agricultural land under seasonal cultivation. In real-world practice, a farmer in Haryana’s water-scarce Mahendragarh district reported that after implementing farm bunding, his guar crop yield increased by 250 kg due to improved soil moisture availability – with income rising by INR 11,000 in a single season.

Erosion control and fertility retention 🔗

Topsoil is the most productive part of any agricultural soil – it holds nutrients, organic matter, and the microbial activity that supports crop growth. When runoff carries topsoil away, it also removes the nutrients bound to soil particles. Bunding slows runoff velocity, causing sediments to settle out before they leave the field. Contour bunding in Mali, supported by ICRISAT, helped retain moisture and nutrients while preventing soil erosion, bringing a 20% increase in income to local populations. Nutrients like nitrogen and phosphorus that would otherwise be lost in eroded sediment are retained within the bunded area, maintaining long-term soil fertility.

Groundwater recharge 🔗

When water infiltrates slowly over a large bunded area, a portion of it percolates beyond the root zone and recharges groundwater aquifers. Water bunds recharge groundwater by promoting infiltration and support biodiversity by creating moist habitats for plants and animals. This benefit extends beyond the individual farm – recharged aquifers support wells and springs that entire communities depend on, making bunding a practice with landscape-level hydrological impact.

Improved crop yields 🔗

The combination of better soil moisture, reduced erosion, and improved fertility directly translates into higher yields. Trench cum bunding was found to improve crop yields by 12-30% over without bunding, with intense rainfall events retaining most of the topsoil in the trenches while allowing safe disposal of excess rainwater. In India, contour bunding has been shown to support a winter crop sown after monsoon water infiltrates behind bunds in semi-arid Rajasthan, effectively extending the productive season beyond the monsoon period.

Drought resilience 🔗

The contour bunding technique creates micro-catchments that intercept runoff, increase rainfall capture, promote water storage and deep infiltration, and reduce gully formation – conditions that collectively support more reliable crop growth even in low-rainfall years. For farmers who depend entirely on seasonal rainfall, this resilience is not just an agronomic advantage – it is a food security buffer.

Design and construction considerations 🔗

Effective bunding requires more than digging up some earth. Bund height is primarily determined by the slope of the land, bund spacing, and the maximum amount of rainfall forecast in the area. Construction should start from the ridge and work down the valley so that any rainfall during construction does not damage already-built sections. Earth should be placed in layers of approximately 15 cm and compacted firmly to ensure structural integrity.

Stabilization is an important step that is often overlooked. Grasses planted on the bund surface significantly extend its lifespan by binding the soil and reducing erosion from direct rainfall impact on the bund itself. In some systems, fast-growing tree seedlings are planted at 3-meter intervals on the crest of the bunds to reinforce them and enhance their stability. Castor oil plants are also used on bund surfaces in parts of India to stabilize the structure while providing an additional income source.

Bunding works best when it is part of a wider land management system. The effectiveness of bunding also scales with adoption – better erosion-control results are achieved when farmers on the same slope coordinate their approach, since water flowing from unbunded upper slopes can overwhelm lower bunds. Community-level coordination therefore significantly amplifies the individual benefits of bunding.

Limitations to be aware of 🔗

Bunding is a valuable but not universal solution. On heavier clay soils, waterlogging near bunds can damage crops, especially during years with above-average rainfall – this is precisely why graded bunds with controlled outlets are recommended on such soils. Contour bunds lose around 5% of cultivable area to the bund structure itself. A lot of labour is needed to maintain and repair the bunds, and if bund spacing is too close, farm operations can be disrupted. Stone bunds can be expensive to construct in areas where stone resources are scarce. These limitations don’t diminish the value of bunding, but they do underscore the importance of choosing the right type for local conditions rather than applying a one-size-fits-all approach.

What do you think? Given that bunding can reduce soil loss by tens of tonnes per hectare annually, why do you think many smallholder farmers in erosion-prone areas still haven’t adopted it – is the barrier more about awareness, labour cost, or land tenure? And with rainfall patterns becoming increasingly erratic due to climate change, how might the design of bunding systems need to evolve to remain effective?

References

1. https://www.soilmanagementindia.com/soil-erosion/bunding/bunding-classification-design-construction-soil-management/15201
2. https://sswm.info/sswm-university-course/module-4-sustainable-water-supply/further-resources-water-sources-hardware/bunds
3. https://www.smsfoundation.org/news/farm-bunding-enhances-agriculture-income/
4. https://unacademy.com/content/difference-between/contour-bunding-and-graded-bunding/
5. https://indiaagronet.com/indiaagronet/Agri%20engineering/contents/Bunding.htm
6. https://agriculture-aajtak.blogspot.com/2023/06/bunding-and-terracing-effective.html
7. https://www.researchgate.net/publication/367637440_Bunds
8. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/soil-moisture-conservation
9. https://www.greener.land/contour-bunds/
10. https://humblebeeorganic.com/permaculture/water-bunds/
11. https://e-catalogs.taat-africa.org/com/technologies/contour-bunding-technique-cbt-contour-bunds-for-water-harvesting