Benefits of Contour Farming in Soil Conservation

Soil erosion is one of the most pressing challenges facing agriculture on sloped land. Every heavy rainfall on an unprotected hillside carries away the thin, fertile topsoil that took centuries to build – along with the nutrients, organic matter, and microorganisms that make it productive. Contour farming, a practice as ancient as the Phoenicians and as relevant as modern precision agriculture, offers a proven, low-cost solution to this problem. By simply changing the direction of plowing – from up-and-down the slope to across it – farmers can dramatically reduce erosion, conserve moisture, and improve soil fertility.

What is contour farming? 🔗

Contour farming is the practice of plowing, planting, and cultivating crops across a slope, following the land’s natural elevation lines – called contour lines – rather than running rows straight up and down the hill. These contour line furrows create a water break, reducing the formation of rills and gullies during heavy rainfall and allowing more time for water to settle into the soil. In contour plowing, the ruts made by the plow run perpendicular to the slope, forming a series of level furrows that curve around the land.

The basic principle is straightforward: when water flows downhill and meets a row of crops or a furrow running across the slope, it slows down. Slowed water infiltrates the soil rather than washing it away. As one agronomist at Sound Agriculture explains, “water will always choose the path of least resistance, so the goal of contour farming is to slow down that water as it travels downhill by farming in strips across the hill instead of up and down the hill.”

The problem with conventional up-and-down-hill farming 🔗

When farmers plow straight up and down a slope, they create channels that guide water rapidly downhill. As the water gains speed, it picks up soil particles and carries them away. This process does not just remove soil – it removes the most fertile topsoil layer, the one that took decades or centuries to develop.

The historical scale of this damage is well documented. During the 1930s Dust Bowl era in the United States, the 1934 Yearbook of Agriculture reported that approximately 35 million acres of formerly cultivated land had essentially been destroyed for crop production, with another 100 million acres having lost all or most of their topsoil. This crisis directly led to the establishment of the USDA Soil Conservation Service in 1935, which made contour farming one of its primary recommended practices.

How contour farming reduces soil erosion 🔗

The ridges and furrows created by contour plowing act as small barriers across the field. The rows form hundreds of small dams to slow runoff water. This slowing effect reduces both the volume and velocity of surface runoff, which in turn reduces its capacity to carry away soil particles.

The results are significant. Sheet and rill erosion is reduced significantly, and in most cases soil loss can be cut by as much as 50 percent where contouring is the only conservation practice used. The Natural Resources Conservation Service (NRCS) similarly confirms that contour farming reduces soil erosion by up to 50 percent compared to up-and-downhill farming.

A practical demonstration of this effect came during the Dust Bowl recovery period. By 1938, the introduction of new agricultural techniques, including contour plowing, had reduced soil loss by 65% despite the continuation of the drought.

Reducing rill and gully formation 🔗

One of the specific erosion mechanisms that contour farming targets is the formation of rills and gullies – the small channels that water carves into unprotected soil during heavy rain. Contour line furrows create a water break that reduces the formation of rills and gullies during heavy precipitation, allowing more time for water to settle into the soil. Once rills deepen into gullies, they become much harder and more expensive to restore. Preventing their formation in the first place is far more practical.

Water conservation: turning rainfall into a resource 🔗

Contour farming does more than prevent soil loss – it actively converts rainfall into stored soil moisture. Farming on the contour can increase water infiltration, thereby reducing the transport of nutrients and organics to surface water and increasing water storage in the soil profile.

Research confirms the scale of this benefit. Contoured fields improve water infiltration rates by 15-20%, directing excess moisture into the soil profile rather than allowing it to flow away. Over time, fields using contour farming retain 30% more water, significantly improving crop yields and sustainability.

Contour farming in high rainfall areas 🔗

High rainfall regions present a particular challenge – heavy downpours can overwhelm unprotected soils in minutes. Contour farming is especially valuable in these settings. Experts say contour farming works best on slopes with gradients between 2 and 10 percent and in areas that receive substantial rainfall, with mountainous regions tending to be ideal.

However, the USDA NRCS notes that the practice becomes less effective in areas with 10-year, 24-hour rainfall of 6.5 inches or greater when used alone. In such cases, contour farming is most effective when combined with additional measures like strip cropping or terracing. On slopes steeper than 10 percent, strip cropping is used alongside contour farming to provide additional protection.

Even in high rainfall zones, contour farming helps by promoting more uniform water distribution across the field, reducing the problem of some areas becoming waterlogged while others stay dry.

Improving soil fertility through erosion control 🔗

Contour farming’s erosion-control benefits directly translate into better soil fertility. When runoff is slowed and sediment stays in place, so do the nutrients bound to it. The ridges created through contour plowing can help trap and retain nutrients within the fields, preventing loss through erosion and improving soil fertility.

Key plant nutrients are particularly vulnerable to erosion losses. Nitrogen, phosphorus, and potassium are all more effectively retained in contour-farmed soils. This is especially true for phosphorus, which binds to soil particles and leaves the field when erosion occurs. Farmers practicing contour farming often find they can reduce fertilizer applications while maintaining or improving yields.

Beyond nutrient retention, keeping organic matter and plant residues on the field supports a richer microbial ecosystem. With plant residues and organic materials remaining on the field, organic matter content rises steadily, and enhanced organic carbon levels foster a richer microbial ecosystem – crucial for nutrient cycling and productivity.

Reducing fertilizer loss and input costs 🔗

The economic case for contour farming is closely tied to its fertility benefits. Contour plowing has been proven to reduce fertilizer loss, power, time consumption, and wear on machines, as well as to increase crop yields and reduce soil erosion. Reducing fertilizer runoff also prevents those chemicals from reaching nearby water bodies, where excess nutrients cause harmful algal blooms through eutrophication.

Financial returns manifest through reduced fertilizer needs, often decreasing by 20-30% by year three as nutrient runoff diminishes. Equipment maintenance costs also tend to decrease because operating machinery across a slope puts less strain on it than repeatedly going up and down hills.

Impact on crop yields 🔗

Better soil moisture and improved nutrient retention naturally translate into higher, more reliable yields. Demonstrations have shown that contour farming, under ideal conditions, will increase yields of row crops by up to 50%, with increases of between 5 and 10% being common.

Field evidence supports this across multiple regions. A study conducted by the Soil Conservation Service and the University of Nebraska found that by retaining moisture and sharing nutrients in the soil, the majority of farmers surveyed reported a 5-10% increase in yields. A long-term study in Iowa found that contour farming reduced soil erosion by an average of 40% while increasing corn yields by 8-12% in dry years due to improved water retention.

Where contour farming works best 🔗

Contour farming is a targeted practice, and its effectiveness depends on matching it to the right land conditions. The conservation practice of contouring is most effective for reducing soil erosion on uniform slopes ranging between two and eight percent, and where conventional planting practices are followed.

Slope length also matters. The practice is most effective on slopes between 100 and 400 feet long. On slopes longer than 400 feet, the volume and velocity of overland flow can exceed the capacity of the contour ridges to contain it. In these situations, additional practices like terracing are recommended.

Soil type plays a role too. Clay soils, which have slower natural infiltration rates, see greater benefit from contour farming than sandy soils that absorb water quickly on their own.

Combining contour farming with other conservation practices 🔗

Contour farming becomes more powerful when integrated with complementary soil conservation methods. Contour farming is most effective when used with other soil conservation methods such as terrace farming and the use of cover crops.

Strip cropping involves alternating strips of ground cover crops, such as legumes or grasses, with row crops along the contour lines. This combines the barrier effect of contours with the anchoring power of diverse root systems, providing even greater erosion control and improving soil fertility through nitrogen fixation.

Terracing is the recommended next step for steeper slopes. By constructing level steps across a hillside, farmers can work land that would otherwise be too steep for sustainable cropping. Contour farming principles applied within each terrace maximize the benefits of both practices.

Cover cropping between cash crop seasons further protects soil from raindrop impact and keeps organic matter building during fallow periods. Studies indicate that properly established cover crops can increase water infiltration rates by 15-30% during heavy rainfall events, making them ideal companions to contour farming systems.

Implementing contour farming: the basics 🔗

The first practical step is identifying and marking contour lines across the field. This can be done with simple leveling tools, or more accurately today using GPS-guided equipment and digital terrain mapping. The NRCS or a local cooperative extension service can help farmers draw contour lines and plan their system.

Once baselines are established, all farming operations – plowing, planting, cultivating, and harvesting – are carried out parallel to those lines. Contouring is a low-cost, low-maintenance conservation practice that basically requires only an established pattern for equipment travel. Permanent markers such as vegetative strips, hedgerows, or fence lines are maintained to guide equipment in subsequent seasons.

Where runoff water concentrates – typically in low-lying areas between contour rows – grassed waterways should be installed to safely channel the water off the field without causing erosion. These vegetated drainage channels are an essential companion to any contour farming system.

A time-tested practice finding renewed relevance 🔗

The history of contour farming stretches back to antiquity. The Phoenicians developed the practice and spread it throughout the Mediterranean, and even Thomas Jefferson described adopting horizontal plowing along the curves of hills in an 1813 letter, noting that every furrow acts as a reservoir to receive and retain water for the benefit of the growing plant. Despite this long record, the practice was largely abandoned during the era of industrial agriculture in favor of simpler straight-line plowing.

Today, with soil degradation, water scarcity, and erratic rainfall patterns becoming more serious concerns globally, contour farming is regaining momentum. Precision agriculture tools – GPS-guided tractors, drone-based terrain analysis, and satellite soil monitoring – are making it easier and more accurate than ever to implement. Farmer field schools in Jamaica and pilot programs in East Africa are reintroducing the technique to communities farming steep hillside plots that face both drought and flooding. The practice that sustained ancient Mediterranean civilizations is proving just as relevant for 21st-century agriculture.

What do you think? If you farm or manage sloped land, are the short-term costs of transitioning from conventional row planting worth the long-term gains in soil health and yield stability? And as extreme rainfall events become more frequent due to climate change, should contour farming be made a standard requirement for agricultural subsidies on sloping land?

References

1. https://www.nrcs.usda.gov/sites/default/files/2022-09/Contour_Farming_330_CPS_Oct_2017.pdf
2. https://en.wikipedia.org/wiki/Contour_plowing
3. https://www.sound.ag/blog/contour-farming-a-smart-approach-to-soil-conservation
4. https://efotg.sc.egov.usda.gov/references/Delete/2007-6-16/ContourFarmingMN.pdf
5. https://efotg.sc.egov.usda.gov/references/Delete/2011-1-1/ContourFarming.pdf
6. https://www.corteva.com/who-we-are/outlook/modern-benefits-to-contour-farming.html
7. https://www.twdb.texas.gov/conservation/BMPs/Ag/doc/4.2.pdf
8. https://www.farmstandapp.com/66352/how-to-implement-contour-farming-for-effective-drainage/
9. https://farmonaut.com/blogs/contour-farming-7-shocking-soil-water-benefits
10. https://www.progressivegardening.com/agricultural-engineering/contouring.html
11. https://kansaspermaculture.org/blog/four-benefits-of-contour-farming/
12. https://extension.usu.edu/agwastemanagement/files/330_UT_CPS_Contour_Farming_2013.pdf