Dairy Management: fertiliser, picking bulls and keeping calves healthy

Aidan Brennan looks at how much nitrogen should be spread now to ensure good grass growth rates for the rest of the spring

Aidan Brennan

12 March 2025

Dairy Management: fertiliser, picking bulls and keeping calves healthy

Fertiliser: Ground conditions are excellent, and with very little rain in the forecast we can expect good grazing conditions to last into next week. Weather is set to turn a bit milder next week too so that is good news for grass growth, which is a concern for many farmers that have 60% or more of the farm grazed. Where average farm cover is below target, these farmers need to turn on the handbrake to ensure that there will be some grass in the diet by the end of March and into April. A key part of this is making sure ground is well fertilised. Going on the Teagasc advice for spreading 212kg N/ha per year, the new maximum for farmers stocked above 210kg N/ha of organic nitrogen, the most that can be spread in February and March is 60kg N/ha which is 48 units/acre before 1 April. A few years ago, the advice was to apply 70 units/acre by 1 April, but with the cuts to allowances, that has reduced.

A key part of this is making sure ground is well fertilised. Going on the Teagasc advice for spreading 212kg N/ha per year, the new maximum for farmers stocked above 210kg N/ha of organic nitrogen, the most that can be spread in February and March is 60kg N/ha which is 48 units/acre before 1 April. A few years ago, the advice was to apply 70 units/acre by 1 April, but with the cuts to allowances, that has reduced.

I know some farmers who are going back to using the higher rates in spring and will cut back further in the second half of the season, when nitrogen from clover, background nitrogen from the soil and N from slurry/soiled water can fill the gap.

Separately, I see the fertiliser manufacturers are putting the date of bagging on the outside of the fertiliser wrapper. This is something that farmers have been looking for for some time so its good to see it happening. The codes will either have the date clearly displayed or else will have the factory code where it was made and the year and day of the year it was bagged.

For example, a code such as F10024340 should be interpreted as F100 being the factory code, 24 being the year and 340 being the day in 2024 which is 5 December. This will be important when looking at protected urea shelf life.

Breeding: The Focus section this week is on spring AI. Many farmers have their bulls chosen already as the demand for sexed semen is high and the last bull run was in November so nothing has changed since. The active bull list is published in Focus and one of the new additions in the list and on the health sub-index is the inclusion of TB. The ICBF says that selecting bulls with a low risk for TB could halve TB numbers nationally. The advice is to avoid using bulls that are high for TB as daughters of these bulls are more likely to go down with TB in the event of an outbreak. There are 15 bulls out of 75 on the list that are high for TB and should be avoided, especially in areas where TB is a concern. The data used by the ICBF when formulating the proof is based on reactors that kill out with lesions.

Calves: Despite the good weather we are in a high-risk time for calves on the farm. March is the traditional time that problems start to emerge in the calf shed. Don’t wait for problems to happen before doing something. It is a good idea to do a full clean out of calf and calving sheds as we approach mid-March. I know some farmers are turning out the oldest calves into sheltered paddocks to take the pressure off sheds.