Spring nitrogen planning: Using excess winter rainfall data

Grass growth has started in parts of the country, but the extreme levels of rainfall across much of the UK are likely to influence early spring nutrient decisions.

At AHDB, we use Met Office data to calculate excess winter rainfall (EWR). This helps farmers adjust nutrient management planning, especially nitrogen.

We show the EWR results in a UK grid of 199 squares (40 km x 40 km) using three categories:

• Low: less than 150 mm
• Moderate: 150 to 250 mm
• High: over 250 mm

These categories link directly to the Nutrient Management Guide (RB209), helping estimate soil nitrogen supply (SNS) for various cropping situations, including grassland.

Although air temperatures are rising and spring feels close, waterlogged or compacted soils can warm much more slowly.

The old rule of spreading fertiliser when daffodils flower may be useful, but local soil conditions are still key.

• Check the EWR for your area and use it to adjust nitrogen applications for grass
• Inspect fields for waterlogging and compaction to reduce nutrient runoff
• Test slurry nutrient content – heavy rainfall may have diluted its value in stores (RB209 has standard figures, but actual values can vary)
• As fuel, fertiliser and feed costs rise, review the nutrient management plan to maximise the benefit from on-farm manures, clover and multi-species leys
• Revisit the basics of grazing management to maximise the animal output from grazed grass
• Plan reseeds to capitalise on the best varieties for the role in the mixture

Fuel, feed and fertiliser costs continue to rise as global conflicts affect supply chains. Even if market returns improve slightly, they’re unlikely to cover higher input costs.

This makes it more important than ever to get the best value from homegrown forage.

Review how you use manures, legumes, grazing and livestock management to support both short and long-term performance.

Plan forage stocks, grazing platforms and livestock numbers to make sure they meet productive livestock needs.

Before applying manures, inorganic fertilisers or introducing seed, check soil pH and nutrient indices.

Use lime where needed and choose a product that suits your soil type and existing nutrient levels, including magnesium and phosphate.

Improving soil structure and biology takes time, but soil can be damaged quickly, for example, through trafficking on wet saturated soils.

Healthy soil helps grass take up nutrients more effectively.

Where nitrogen is used at higher rates, ryegrass-rich swards usually give a better response than older or secondary grass species.

Precision application improves utilisation of expensive bought in fertilisers and minimises risks of runoff or luxury uptake.

Target nitrogen to fields with the greatest potential and where improvements will support growth rates or milk yield.

Farm manures provide nitrogen, phosphorus and potassium. Account for these nutrients when planning artificial fertiliser applications.

You can increase the value of solid manures by composting, which raises dry matter and concentrates nutrients.

Slurry and digestate processing can also help improve composition and spreadability.

Clover can fix 150–200 kg N/ha when soils are warm and pH, phosphorus and potassium levels are correct.

It also provides crude protein levels (14–20%) and improves soil health.

Managing rotational grazing and residuals, as well as silage, along with soil indexes, can encourage clover content and forage quality.

Multi-species swards can offer good late-season growth.

Legumes support nitrogen supply and protein content, and their deep roots, along with those of herbs and grasses, help improve soil structure and nutrient scavenging.

SFI and SFS payments can help support their use.

Reviewing rotational grazing plans each week can help optimise grass use and livestock performance.

This allows you to prioritise productive stock and link grazing decisions with feed planning for dairy cows.