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Nitrogen Use Efficiency = Cleaner Water

Deirdre Glynn, Teagasc ASSAP Advisor and Dr. David Wall, Teagasc Researcher both define Nitrogen Use Efficiency (NUE) here. They discuss losses of Nitrogen and how we can avoid this going forward through soil testing, nutrient planning, responsible fertiliser and slurry spreading and more

Nitrogen use efficiency (NUE)

Nitrogen use efficiency (NUE) is the quantity of nutrient recovered by a crop relative to the nutrients supplied from soil, applied fertilisers, manures and ultimately how much is recovered in the end product we are selling in terms of milk, meat or crops. Efficient use of nitrogen is essential to achieving maximum crop growth and achieving a greater return on each kg of fertiliser you invest in.Planning helps to optimise the use of farm nutrients, maintain and improve soil health, reduce excessive nutrient build up and lessen environmental losses.

Losing from the system

Grassland based systems of production are “Leaky” by nature in terms of N loss. Current National Farm Survey Sustainability reports put Irish dairy farms at 25% NUE in terms of their ability to recover N from their N imports (feed, fertiliser etc.) via milk sales, cattle sales and grass/crop yield. With an industry target of 35% looming there is scope for improvement.

Matching nitrogen fertilizer use to stocking density and grass growth on the farm at different times of the year avoids excessive use

Application rate and application date of fertilizer nitrogen (N) are important factors in determining grass production response and N recovery. Applying nitrogen fertilizer ‘little and often’ during the growing season gives most efficient response in terms of grass growth and economic return.

What can we do in 2021?

  • Soil Test and develop a nutrient management plan with you advisor
  • Monitor soil temperature, provided conditions are suitable, nitrogen application should coincide with the onset of spring growth – this happens once soil temperatures reach 5.5 degrees C or above and climbing
  • Ensure heavy or prolonged rain is not forecast when spreading fertiliser/slurry and don’t spread if machine is tracking ground
  • Adhere to buffer zones
  • LESS (Low Emission Slurry Spreading) increases the amount of N recovered for slurry and allows for a reduction in applied fertiliser N
  • Use of grass-clover systems. White clover can increase the tonnes dry matter grown (+ 1 – 1.5 t DM/ha) increase animal performance as it is a higher quality feed, and it can reduce the need for chemical nitrogen which increases the nitrogen use efficiency (NUE) on farms
  • Calibrate your fertiliser spreader, this makes sense financially and environmentally

No farmer wants to pollute a waterway or well water under their land that their family or neighbours are drinking and improving nitrogen use efficiency on your farm will reduce nitrogen losses to water. In this short clip, Dr. David Wall, Teagasc, goes through what you can do to prevent this such as soil testing and developing a nutrient management plan with your advisor; monitoring soil temperature (5.5 degrees C or above and climbing); ensuring heavy or prolonged rain is not forecast when spreading fertiliser/slurry and not spreading if machine is tracking ground; adhering to buffer zones; using LESS; using grass-clover systems and calibrating your fertiliser spreader.

For more info see www.watersandcommunities.ie  www.catchments.ie  and www.teagasc.ie/waterqualityweek