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Eamon & Donnchadh McCarthy January/February Update

Making soil fertility a priority

Making soil fertility a priority

  • Take soil samples
  • Plan fertiliser & slurry applications
  • Source fertiliser (including protected urea)
Scanning results & DNA calf registration

Scanning results & DNA calf registration

  • 22/23 autumn cows are in calf after 6.5 weeks breeding season
  • All calves are being DNA registered on the farm
  • The genomic results are back faster to help make breeding decisions for replacements
Mineral results

Mineral results

  • Mineral sample results show low trace elements
  • A mineral bolus is covering some of the low trace elements
  • However macro minerals are not covered

Soil Fertility

Eamon & Donnchadh took 22 soil samples on their farm between winter 2021 and spring 2022. The results showed that 68% of the farm had a pH less than the target of 6.2 and that a total of 134t of lime was required to correct this. Lime delivers a 7:1 return on investment and increases the response to nitrogen, phosphorus and potassium in organic and chemical manures, as well as releasing up to 70kg N/ha/year soil nitrogen. As such, the McCarthys spread 70t of lime in October and 64t in December to get it working ASAP.

Eamon & Donnchadh are hoping to incorporate clover onto their farm over the next few years to help reduce their chemical nitrogen usage. Correcting the soil pH is the first, most important step, in working towards this. The second step is to get the phosphorus and potassium indexes to a minimum of index 3.

Currently, 62% of the farm is in index 1 or 2 for phosphorus and 42% is in index 1 or 2 for potassium. Slurry will be spread using the dribble bar and targeted to fields that have the highest nutrient offtakes (i.e. silage fields); then to lower P and K index fields. The dung produced on the farm is ploughed into the tillage ground in the autumn. Due to the lower soil indexes, 18-6-12 is the main compound used on grassland and 13-6-20 is used on tillage ground to help improve the indexes.

The slurry produced by suckler cows on the farm was tested last year and showed the nutrient content per thousand gallons. This showed an average result of 10.15 units nitrogen, 5.76 units phosphorus and 28.03 units potassium per 1,000 gallons of slurry. As the suckler cows are on the slats again this year, the slurry sample results should be similar. This allows Eamon & Donnchadh to spread the required amount of chemical fertiliser to top up silage fields and on grazing ground, which is both financially and environmentally beneficial. Spreading slurry with the dribble bar in spring is also retaining 3 extra units of nitrogen per 1,000 gallons.

As they are following a nutrient management plan based on the farm soil sample results, Eamon and Donnchadh have forward bought most of their fertiliser for 2023 due to concerns over availability and price. Aside from compounds, their main chemical nitrogen source is protected urea. This is cheaper than CAN and straight urea per effective unit of nitrogen, and also produces 71% less nitrous oxide than CAN and 78% less ammonia emissions than urea. Eamon and Donnchadh have been using protected urea for the last few years on the farm and are very happy with the results.


22/23 cows are in calf for autumn herd. They were bred from 3rd Oct to 17th Nov; 6.5 weeks in total. The spring herd are due to start calving from 10th February.

All male and female calves born on the farm are registered by DNA calf registration. Eamon & Donnchadh have been involved in this pilot for the last 4 years, and this year all suckler farmers in the Future Beef programme had the opportunity to participate in it too, through ICBF and the Signpost programme.

Eamon sees it as the “way forward”. He would have been genotyping some cattle on the farm as part of the Beef Data and Genomics Programme anyway, for which a fee of €22 had to be paid. This way the calves are genotyped at birth, which saves labour compared to tagging them at 2-3 months of age, and he has genomic results back before heifers are selected for breeding. If there is any issues with paternity, it is also picked up. He finds it very simple to do – there are two separate tag types sent out from his provider. One tag set is for the BVD sample and is sent to the BVD lab, with the second set including a different coloured vial for the genomic sample which is sent to Wetherby’s lab. It costs €10 per animal (including the tag set cost) and Eamon finds the turnaround time quite fast (~10 days), but as he is not selling calves at birth it is not a major concern.


A mineral analysis was taken for the silage that the suckler cows are eating on the farm. Eamon and Donnchadh gave boluses to all of the suckler cows. They were given 2 boluses each which are reported to last up to 6 months. Each bolus contains:

  • 30,000 mg copper (providing 333 mg/day)
  • 5,000 mg iodine (providing 55 mg/day)
  • 500 mg Selenium (providing 5.6 mg/day)
  • 500 mg cobalt (providing 5.6 mg/day)

These meet the trace element requirement for suckler cows pre-calving as recommended, although no manganese or zine is being provided.

However they do not provide any major elements which need to be fed daily. At present there is no major issue on the farm from mineral deficiencies and the mineral sample results show that the major elements (phosphorus, potassium, calcium, sodium) are at normal to high levels in the silage being fed to the cows. The trace elements are low to very low on the farm, and while the bolus is providing the minerals outlined above, no zinc or manganese is being provided, nor are vitamins A, D3 and E.

See the Mineral Reference Sheet for further information.

Mineral results