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Improving land drainage to reduce emissions
Enhancing or renovating land drainage can reduce greenhouse gas (GHG) emissions and promote soil health.
Improved drainage helps unlock the full potential of farmland, leading to higher yields and a more resilient cropping system. Wet or poorly drained areas can be difficult to manage and are often linked with higher emissions, especially nitrous oxide (N2O). Even basic drainage maintenance can deliver quick, noticeable improvements, making it a cost-effective step towards more sustainable and productive farming.
Benefits for the environment and your farm business
Improving land drainage doesn’t just reduce emissions – it also supports better soil health, crop and grass performance, and farm profitability. Here’s how:
- Wet soils are a key source of N2O emissions, especially where nitrogen fertilisers are applied
- Improved drainage reduces waterlogging, lowering these emissions and improving fertiliser efficiency
- When better drainage leads to higher yields, emissions per tonne of crop produced also decreases
- Well-drained soils are less prone to compaction, promoting healthier root growth and better yields
- Drainage helps reduce surface runoff and soil erosion, especially during heavy rainfall
- They also reduce surface run-off rates and soil erosion during heavy rain
- Healthier, better-structured soils with improved infiltration help reduce phosphorus and pesticide losses
- Less structural damage also means nutrients are used more effectively, supporting plant growth
- Drained soils maintain a better balance of air and water, improving soil structure and microbial activity
- This improves soil structure and extends the autumn working window
- Crops in well-drained soils establish faster and more evenly
- Strong growth helps outcompete weeds, reducing the need for herbicides
- Better-drained fields are easier to access with machinery, improving timeliness of operations such as drilling, spraying and harvesting
- This supports more efficient fieldwork and reduces the risk of delays due to wet conditions
- Improved drainage also provides better traction for machinery, helping reduce compaction
Production benefits from field drainage are usually greatest in:
- High-rainfall areas
- Heavy clay soils
- Medium soils growing potatoes, root and high-value crops
- Low-lying permeable soils where the groundwater level is close to the surface
It makes good business sense to maintain drains and ditches. They capture higher yields and crops will be healthier. This should make justifying the cost straightforward.
How to evaluate and improve drainage
Check for signs of poor drainage
Common signs of poor drainage include:
- Standing water in fields that persist after rainfall
- Submergence in water of land drain outfalls
- Slow-moving water or a excessive silt build-up of in ditches
- Culvert pipes submerged beneath water levels in ditches
Take time to assess whether your existing drainage system still meets your farm’s needs. If it was installed decades ago, changing soil conditions, field layouts, or farming practices may mean it no longer performs as effectively as it once did.
Clean outfalls and ditches
Field drainage systems rely on free-flowing outfalls and ditches to function effectively. If these become blocked, water backs up through the system, reducing its effectiveness or causing it to fail altogether. Regular maintenance of ditches and outfalls is a simple, cost-effective way to protect both productivity and soil health.
- Clear ditches and outfalls regularly, especially in autumn before wetter weather
- If an outfall is blocked, it may be possible to dig up the pipe on one or both sides and use drain rods to clear the obstruction. You could also hire a contractor with specialist drain jetting equipment
- Silt-filled pipes are common in soils with fine sand or silt, cleaning them promptly can prevent long-term issues
Replace field drains
If the field drains have failed, they will need to be replaced:
- Use the same diameter drain as the existing one. Consider the life expectancy of your drains
- However, if the drain is a carrier drain or culvert, an increased pipe diameter would reduce the risk of blockage or excess flows collapsing the pipe in the future but care is needed to avoid increasing flood risk downstream
- Main drains are usually installed by specialist companies
Use mole drains
Many farmers create mole drains to make their drainage systems more efficient:
- These are unlined channels formed in a clay subsoil to channel water towards main pipe drains or ditches
- Ideal for when natural drainage needs improving on heavy land
- Not suitable for controlling rising groundwater or in areas prone to flooding
- Tend to last 5–10 years, depending on soil type and climate
Find out more on reducing emissions on farm
Further information on improving land drainage
