Early season fertiliser planning is more important than ever in 2019 compared to other years because in general farmers fed a lot more concentrate in 2018 and that will affect what fertiliser you can spread in 2019.

These were the words of Teagasc specialist Mark Plunkett as he spelled out the changes in fertiliser advice for 2019 in Johnstown Castle.

Mark explained: “In the east and south particularly, farmers fed a lot more concentrate in 2018 compared to 2017 and the only way to see the impact of this is that farmers must complete a fertiliser plan now.

“In some cases, because of the higher feed in 2018, the phosphorus allowance will be very much reduced. There also are a number of changes to the N and P calculations related to the Nitrates Directive.”

Mark was explaining the basis to the N, P and K advice and changes to legislative N and P limits to advisers and farmers attending the winter milk masterclass for the Agricultural Science Association in Johnstown Castle.

Mark’s rule of thumb on early nitrogen is that you must look at a number of factors and then make a decision.

The six key factors he works with at this time of the year are:

  • Soil temperature: you need 5°C to 6°C for growth.
  • Cold weather: little growth so no demand and if wet then risk of nitrogen loss.
  • Nitrogen rate: max 30kg N/ha (half bag of urea per acre) or 2,000 to 2,500 gal of cattle slurry.
  • Ammonium fertiliser best so that’s urea-type products.
  • Paddocks with strong grass covers apply urea and bare fields apply slurry.
  • Target rye grass dominant swards and dry, sheltered, free-draining fields first.
  • On phosphorus, his advice is apply 50% of the phosphorus in the second or third application of fertiliser (March/April), with any remaining allowance applied in May and June at peak grass growth.

    On potassium, his advice is apply index 3 rates in spring and apply potassium build-up rates in August and September.

    For 2019, Mark went through a number of changes that are noteworthy:

    New nitrogen allowances

    The annual maximum fertilisation rates of nitrogen on grassland have changed and now slurry nitrogen is deducted from the whole farm nitrogen allowance.

    So the key Table here now is Table 1.

    For those farms stocked less than 170kg organic nitrogen (2 cows/ha) the available nitrogen ceiling is 206kg N/ha.

    If grassland stocking rate is between 171 and 210, the ceiling is 282kg of available nitrogen.

    Over 211 kg/ha and the maximum is 250kg of available nitrogen.

    Phosphorus allowance changed

    The change in the current Nitrates Directive is that slurry phosphorus is now excluded from the whole farm phosphorus allowance calculations, so in essence it’s a simplification to the slurry part of the phosphorus calculation. Where slurry is applied to fields that are P index 1 or 2, the phosphorus in the slurry is deemed to be 50% available in the year of application. This will increase the farm’s P allowance as the unavailable P can be imported on to the farm as chemical P to ensure the grass has sufficient P during the growing season on low-fertility fields. This will be important in 2019 where P is limiting on farm (Table 2 shows the new P allowances as per the Nitrates Directive).

    The big change in phosphorus allowance is where a phosphorus build-up strategy is adopted for the farm. Then Table 3 comes into play and you are allowed a higher phosphorus allowance (at index 1 and 2).

    So you can see instead of a phosphorus allowance of 33kg/ha for soils phosphorus index 1 (130 to 170) in the phosphorus build up scenario it’s 63kg/ha, almost twice the allowance.

    For P index 2 soils, the allowance moves from 23kg to 43kg. These are significant changes in allowances and to be eligible to use these allowances farmers must be stocked over 130 kg/ha, have soil samples taken every 5ha, have a fertiliser plan and have completed a short training course.

    Concentrate phosphorus

    As a general rule, farmers, particularly in the east of the country, fed a lot more concentrate to cows and youngstock in 2018. Most farmers will have fed between 500kg and 1,000 kg of concentrate per cow or per livestock unit.

    This was an outcome of poor grass growth in spring and drought in the summer. As a result, depending on your farm stocking rate and how much feed you actually fed, your phosphorus allowance will be reduced as per Table 4.

    For example, if you are stocked at 250kg organic nitrogen and you fed 1.5t/livestock unit then effectively your phosphorus allowance is reduced by 17kg of phosphorus per hectare. So the if in P Index 3 rates then your allowance is reduced from 19kg down to 2kg/ha.

  • It’s important to complete the farm fertiliser plan now so that you can adjust for phosphorus in feed that was fed out in 2018.
  • If you haven’t urea out yet then as this week is very cold you are better to hold off until weather softens again. Some farmers have spread over a week to 10 days ago and it’s a job done.
  • Plan to spread 50% of your phosphorus allowance in March and April.
  • 1,000 gallons of slurry is equal to six units of nitrogen, five units of phosphorus and 32 units of potassium (6-5-32 of NPK). If you apply slurry with a band spreader, you hold an additional three units of available nitrogen.
  • Target slurry to low-P fertility fields as this will increase the farm’s chemical P allowance.