Spring nitrogen planning: Using excess winter rainfall data

The Agricultural and Horticultural Development Board is using Met Office data to calculate excess winter rainfall (EWR) to help farmers adjust their nutrient management planning, especially nitrogen.

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

AHDB showed the EWR results in a UK grid of 199 squares (40km x 40km), using three categories:

Low: less than 150mm;
Moderate: 150-250mm;
High: over 250mm.

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, AHDB said.

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

Here are some practical steps to take from AHDB:

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.

Managing costs through grassland planning

Fuel, feed and fertiliser costs continue to rise as global conflicts affect supply chains.

Even if the market returns improve slightly, they are unlikely to cover higher input costs, AHDB said.

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

AHDB recommended that farmers review how they use manures, legumes, grazing, and livestock management to support both short and long-term performance.

Forage stocks, grazing platforms, and livestock numbers should also be planned to make sure they meet productive livestock needs.

Soil health

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.

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, AHDB said.

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

Make the most with your manure

Farm manures provide nitrogen, phosphorus and potassium so farmers should account for these nutrients when planning artificial fertiliser applications.

Farmers 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.

Nitrogen from clover and legume-rich swards

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

Clover also provides crude protein levels (14-20%) and improves soil health.

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

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

AHDB also reminded farmers to review their grazing plans regularly, as it can help optimise grass use and livestock performance.

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

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