Eamon and Donnchadh McCarthy Soil Fertility Update

Eamon and his son Donnchadh are farming in Carrigeen, Glendine, Youghal, Co. Waterford. Both work part-time on the farm. In addition, Eamonn works as a relief milker and Donnchadh has a full-time off farm job.

Eamon & Donnchadh took 22 soil samples on their farm between winter 2021 and spring 2022. The results (see below) 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. As per the table below, 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.