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examBoard: Cambridge
examType: IGCSE
lessonTitle: Soil Erosion in Agriculture
Soil erosion is one of the most serious environmental threats facing modern agriculture. It occurs when the top layer of soil which contains most of the nutrients plants need to grow is removed by wind, water, or farming activities. Every year, about 24 billion tonnes of fertile soil are lost worldwide, threatening food security and ecosystem health.
Key Definitions:
Soil is far more than just dirt! It takes over 500 years to form just 2.5 cm of topsoil under natural conditions. Soil provides:
Soil is being lost 10-40 times faster than it's being replaced. The UN estimates that by 2050, soil erosion could reduce crop yields by up to 10% globally equivalent to removing millions of hectares of farmland from production. In the UK alone, about 2.9 million tonnes of topsoil are eroded annually.
Soil erosion occurs through different processes, each with distinct patterns and impacts on agricultural land:
Water is the most common agent of soil erosion in many parts of the world, including the UK. It occurs in several forms:
Raindrops hit bare soil with surprising force, dislodging soil particles and destroying soil structure. This is the first stage of water erosion.
Water flows as a thin layer across the soil surface, removing soil particles evenly. Often hard to spot until significant damage occurs.
Small, shallow channels form as water concentrates in low spots. These rills can be removed by normal tillage but indicate advancing erosion.
When rills deepen into larger channels that cannot be crossed by farm machinery. Gullies can grow several metres deep and wide, severely damaging farmland and creating hazards.
Occurs when flowing water removes soil from the banks of streams and rivers. This can be accelerated when riparian vegetation is removed for farming.
Wind erosion is particularly problematic in dry areas or during drought periods. It affects about 28% of agricultural land globally and occurs through:
Fine soil particles are lifted into the air and can be carried great distances. These dust storms reduce visibility and can transport soil nutrients hundreds of kilometres away from farmland.
Larger soil particles bounce along the ground (saltation) or roll along the surface (surface creep), causing abrasion damage to crops and further soil dislodgement.
Often overlooked, tillage erosion is caused directly by farming practices. Each time soil is ploughed or tilled, it moves downslope. Over time, this thins soils on hilltops and ridges while building up soil at the bottom of slopes. Studies show tillage erosion can move more soil than water or wind in some landscapes.
The consequences of soil erosion extend far beyond the farm gate, affecting both the environment and human society:
Farmers and land managers can use various techniques to protect soil from erosion:
Growing plants like clover, rye or vetch between main crop seasons protects bare soil, adds organic matter and improves soil structure. Can reduce erosion by up to 80%.
Ploughing and planting across slopes rather than up and down. Creates natural barriers to slow water flow and reduce soil movement downhill.
Reducing or eliminating ploughing to maintain crop residue on the soil surface. No-till farming can reduce erosion by 90% compared to conventional tillage.
Growing different crops in sequence to improve soil structure, break pest cycles and maintain soil cover throughout the year.
Permanent vegetation zones along waterways that trap sediment and filter runoff before it reaches water bodies.
Creating level platforms on slopes to reduce gradient and slow water flow. Common in hilly regions worldwide.
Once one of the most eroded places on Earth, China's Loess Plateau has been transformed through a massive soil conservation project. Starting in 1994, the project:
Results: Soil erosion reduced by 60%, agricultural production increased by 300% and over 2.5 million people lifted out of poverty. The project shows how severe erosion can be reversed with coordinated action.
East Anglia's light sandy soils are particularly vulnerable to erosion. In 2013, severe wind erosion in Norfolk and Suffolk damaged over 10,000 hectares of farmland, with some fields losing up to 2cm of topsoil in a single day.
Farmers have responded by:
These measures have reduced erosion rates by up to 75% on participating farms while improving soil health and biodiversity.
As climate change brings more extreme weather events, soil conservation becomes even more critical. New approaches include:
Remember that healthy soil is the foundation of sustainable agriculture. By understanding erosion processes and implementing conservation practices, farmers can protect this vital resource for future generations.
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