ADLib Glossary (N)

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Best Nitrogen Fertiliser Practice

The fertiliser N requirements of any crop is the amount of N that is economically justified. Crops acquire nitrogen from the soil, atmosphere and organic manures as well as from N fertilisers. Over fertilisation may reduce yields especially where lodging, disease or other problems are evident. Profits may also be reduced by over-spend on fertiliser products. In addition, over fertilisation can result in losses of N to the environment via denitrification, nitrate leaching to groundwater and volatilisation as ammonia.

Best Practice Guidelines

  • Assess nitrogen fertiliser requirements each year in every field. This ensures that only the amounts required are applied and makes for efficient use of resources. The Fertiliser Recommendations software module in the EMA Technical system can help with identifying requirements.
  • Avoid the temptation to be generous with fertiliser. This can encourage problems and is a waste of fertiliser. It may also cause excessive nitrate leaching.
  • Estimate N residues from previous cropping.
  • Always take in to account the contribution of organic manures and /or other soil conditioners towards N requirements.
  • Always adjust N recommendations according to soil type (texture, organic matter content and depth) and excess winter rainfall.
  • Be prepared to modify plans if unusual weather or growth occurs.
  • Be cautious when adjusting recommendations by anticipated yields.
  • Use wheat grain N content to check the success of your previous nitrogen policy.
  • Consider monitoring the green canopy to improve decisions.
  • Reduce losses of N from organic manures by spring applications and rapid incorporation into the soil.
  • Consider starter fertilisers for crops such as onions, lettuce, parsnips and maize.

Over and uneven applications may cause considerable problems. An excess of nutrients can cause crop lodging in cereals, excessive top growth in root crops and overall poor quality, whilst a nutrient shortage may lead to reduced yields. Over application of inorganic fertilisers, to compensate for the uncertainties of manure nutrient supply, will increase nutrient losses to the environment and possibly contribute further to crop quality problems as well as reducing profitability. Although precision farming is a possible solution current research has shown that normal equipment, as long as it is properly set up, well calibrated and carefully managed, is capable of achieving satisfactory results on many farms.

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