Simple and effective use of organic fertilisers and nutrient management planning

Strategic dairy farm host Andrew Gilman, from Statfold Farm, aims to use nutrient managing planning to help him make the most effective use of slurry on his silage ground.

With increasing pressures on fertiliser prices and product supplies, Andrew is keen to make the most of nitrogen from slurry and to improve soil and sward quality – hopefully to reduce purchased fertilisers in the future.

In an on-farm meeting on 28 April 2022, grassland specialist Chris Duller discussed the role that nitrogen plays in producing low cost, high quality forage – and how that by reducing nitrogen fertiliser use there is a danger that you simply end up buying more purchased feeds and extending your housing period.

Reducing nitrogen rates should be possible for everyone, but to physically grow 12t DM/ha of ryegrass you need to supply almost 400kg N/ha – from fertiliser, manures and soil organic matter.

If there’s less nitrogen from the bag then you’ll have to make sure soils are in good health to supply more nitrogen from mineralisation, or that swards contain enough clover to fix nitrogen, or that you take steps to increase the amount of nitrogen you retain in the system when you spread slurry.

Nitrogen applications are cost effective where they achieve a high response. If 1kg N grows 30kg DM of grass, then at current prices that’s only costing you about 8p/kg DM to grow - factor in spreading costs and utilisation losses and it’s still under 14p/kg DM (compared to feed at 35p or more).

  • Achieving a response of 30:1 from nitrogen
  • High ryegrass content (70%+)
  • Optimal soil pH and PK levels
  • Sulphur supply
  • Good soil structure
  • Correct product choice
  • Timing/soil and weather conditions
  • Accurate spreading

Efficient slurry spreading at Statfold is currently slightly compromised by the fact that sand bedding limits their use of low emission spreading – and most goes out with a splash plate.

If Andrew implanted sand separation then nitrogen recovery from slurry could be boosted by 10-20% if slurry can go out through a trailing shoe or shallow injector.

On the farm walk the group of farmers looked at contrasting soil structure of two different soil types and discussed management strategies to reduce problems and mechanical operations to correct any damage.

The group also discussed improving sward quality and strategies to increase and maintain clover in the swards.

Further Resources

Cost benefit calculator for nitrogen fertiliser use on grassland

Nutrient Management Guide (RB209)

The Forage First guide

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