Early grass growth (January/February) is variable and response to early nitrogen is often very low leading to poor recovery of applied urea or CAN. Careful consideration of soil and prevailing weather conditions is needed prior to applying N early in the growing season. Early N applications need to be decision-based rather than calendar-based.

Early N application and grass yield

Figure 1 shows the yield response to the application of 32 kg N/ha at four-week intervals from 18 January between 2013 to 2018. The graph shows limited response to N fertiliser applications in January and early February and much higher responses to N applied from March on. With 1 kg of grass grown worth approximately €0.18 it will take approximately 4-5 kg of additional grass growth per kg N applied to pay for early applications of urea or CAN fertiliser. Therefore, apply early N based on the decision table to maximise the response to early applied N.

If grass response to applied N is low or absent, N loss from the soil and financial loss of fertiliser resources is more likely during this early spring period. For this reason, decision-based early N application should be used. Table 1 provides decision support guidance on the 1st application of early N.

Source of early N

  • Ammonium or ammonium forming fertilisers such as slurry, protected urea or urea are safer from nitrate loss by leaching (water quality) and denitrification (greenhouse gas).
  • Where tanks must be emptied, use slurry as your early N on the driest fields but keep away from watercourses. Low-emission spreading of 22m3/ha (2000 gal/ac) will supply 23kg available N/ha (18 units N/ac) which is adequate to support up to 250kg to 500kg of grass dry matter (DM) under good early spring growing conditions (ie 10 to 20 kg per kg) .
  • Protected urea

    Research suggests protected urea has the potential to be a large contributor to helping Irish agriculture meet national commitments to reduce national greenhouse gas emissions and ammonia emissions.

    Using CAN – switch to protected urea (GHG saving).

    Yield and N efficiency effect? Same yield and N efficiency.

    Using urea – switch to protected urea (ammonia saving).

    Yield and efficiency effect? Small yield increase and significant N efficiency gain, there may be some potential to cut N application rate slightly when substituting protected urea for urea.

    Slurry spreading method

    Teagasc recommends use of trailing shoe or band spreader to retain N for grass growth, limit sward contamination and because of the new national commitments to reduce national ammonia loss.

    Slurry timing

    Focus on being ready for spring application of slurry just in advance of the rapid increase in growth rates which typically occurs in March. Consider getting a contractor with low-emission spreading equipment.

    1 Saving time on the farm for other key tasks.

    2 Retaining more N where a low-emission spreader is not available on the farm.

    3 Benefiting soil structure and subsequent yields if an umbilical system is chosen.

    4 More even spread of nutrients across the spread width.

    Fertiliser planning

    Prepare a fertiliser plan based on recent soil test results. A fertiliser plan will give the following:

  • Show fields that require lime over the next four years.
  • A field plan for the application of farm manures (cattle slurry/FYM).
  • Detailed soil fertility maps on a field by field basis.
  • Identify fields that need extra P and K to build soil fertility.
  • Field by field advice for N, P and K for your farm.
  • A list of fertilisers (shopping list) suitable for the soils on your farm.
  • Ensures compliance with farm maximum limits as per new National Action Programme (Nitrates).
  • Contact your local adviser/consultant to prepare/update the farm fertiliser plan for 2019 on the NMP Online nutrient management programme. This is a key planning tool for the efficient use of lime, manures/slurries and targeted application of fertilisers based on recent soil test results.