Database results:
examBoard: Cambridge
examType: IGCSE
lessonTitle: Contour Ploughing Methods
Soil erosion is one of the biggest threats to agricultural sustainability worldwide. Every year, millions of tonnes of fertile topsoil are washed away by rain or blown away by wind. Contour ploughing is one of the most effective methods farmers use to combat this problem.
Key Definitions:
Contour ploughing was widely promoted in the United States during the 1930s Dust Bowl era, when severe drought combined with poor farming practices led to catastrophic soil erosion across the Great Plains.
When farmers plough up and down a hillside, they create channels that allow water to flow straight downhill, picking up speed and soil along the way. This is a recipe for disaster! Contour ploughing works by creating ridges and furrows that follow the natural shape of the land. These act like mini dams that slow down water runoff and give it more time to soak into the soil.
When rain falls on a sloped field, gravity pulls the water downhill. If the field is ploughed up and down the slope, water flows quickly along the furrows, gaining energy and carrying soil particles with it. Contour ploughing creates barriers to this flow, reducing the water's velocity and its ability to carry soil.
Research shows that contour ploughing can reduce soil erosion by up to 50% on moderate slopes. It's most effective on slopes with gradients between 2% and 10%. On steeper slopes, additional measures like terracing may be needed for better protection.
Farmers have developed several variations of contour ploughing to suit different landscapes and farming needs. Here are the main methods:
The basic technique where all field operations (ploughing, planting, etc.) follow the contours of the land. This is suitable for gentle slopes and requires minimal investment.
Alternating strips of different crops (like corn and hay) along the contours. The strips with dense vegetation slow runoff from the less protected crop strips.
Building small earthen ridges along contours to hold water and soil. These are particularly useful in areas with seasonal heavy rainfall.
For more challenging landscapes or severe erosion problems, farmers might use these enhanced methods:
The Loess Plateau in China suffered from severe soil erosion for centuries. Since the 1990s, a massive restoration project has transformed the region. Contour ploughing, combined with terracing and reforestation, has reduced soil erosion by over 60%. Crop yields have increased and previously abandoned land is now productive again. This project demonstrates how contour ploughing can be part of a comprehensive approach to land restoration.
Implementing contour ploughing requires some specific tools and approaches:
While traditional ploughs can be used, special contour ploughs are designed to work across slopes. Modern GPS-guided tractors can help farmers maintain precise contour lines even on complex terrain. A simple A-frame level can be used in smaller farms to mark contour lines before ploughing.
1. Survey the land to identify the slope direction and gradient
2. Mark contour lines at appropriate intervals
3. Establish permanent guide lines for future operations
4. Plan for water outlets where excess runoff can be safely directed
Like any agricultural technique, contour ploughing has its strengths and weaknesses:
During extreme rainfall events, contour furrows can fill with water and break, creating concentrated flow that may cause even worse erosion than if the land hadn't been contour ploughed. This is why it's important to include overflow channels in the design.
The specific approach to contour ploughing varies depending on local conditions:
In dry areas, contour ploughing focuses on water conservation. Deeper furrows may be used to capture and hold limited rainfall.
Where rain is abundant, the emphasis is on safely directing excess water off the field without causing erosion.
In steep terrain, contour ploughing is often combined with terracing to create stable growing platforms.
For maximum effectiveness, contour ploughing works best as part of a comprehensive soil conservation strategy:
Rwanda, known as "the land of a thousand hills," faced severe erosion problems that threatened food security. Since 2007, the government has promoted a combination of contour ploughing and radical terracing. Over 900,000 hectares have been protected using these methods. Crop yields have doubled in many areas and soil loss has been reduced by up to 90%. This programme shows how contour farming can be successfully implemented at a national scale.
Modern technology is making contour ploughing more precise and effective:
As climate change brings more extreme weather events, including heavy rainfall and drought, contour ploughing will become even more important for protecting soil resources and ensuring food security.
Contour ploughing is a time-tested method for preventing soil erosion on sloped land. By working with the natural contours of the landscape, farmers can slow water runoff, increase infiltration and keep valuable topsoil in place. While it has some limitations, particularly on very steep slopes, contour ploughing remains one of the most cost-effective soil conservation techniques available. When combined with other sustainable farming practices, it forms a key part of responsible land management.
For your iGCSE Environmental Management exam, remember to discuss both the benefits and limitations of contour ploughing. Be prepared to explain how it works and why it's effective at reducing soil erosion. Case studies can help you demonstrate real-world applications.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.