'Soil sampling ensures I'm making the best use of expensive fertiliser'

Peadar O'Droscoll, Teagasc Signpost Programme and Carbery Monitor farmer, discussed the importance of soil sampling and his plan for clover establishment in the March edition of the Teagasc Signpost Programme newsletter.

I milk 70 cows in Church Cross, Skibbereen, the home of our Olympic medal rowers. I supply milk to Drinagh Co-op, which is then processed by Carbery. 

The farm is fragmented and consists of 46ha with an overall farm stocking rate of 2.3LU/ha on a grazing platform of 30ha. I sold 450kg of milk solids per cow in 2022 to Drinagh Co-op. The herd is spring calving with 85% of the herd calving in six weeks, with a calving interval of 368 days. The herd's EBI is €144; the heifers that joined the herd in 2022 had an EBI of €172. I rear all replacements on farm using the outside blocks of land, which is also used for silage production.

Derogation

I am currently in derogation, but I have been taking soil samples on a regular basis before I was required to do so for derogation purposes. I get my derogation plan done each year by my Teagasc advisor, Patrick McCarthy.

Soil sampling

I like to take the samples in late December or early January. This is because this is the longest time away from any slurry or fertiliser applications that could influence the results. I usually take the samples myself using a proper soil corer. My advisor tells me it is important that I get a full 100mm sample each time I push the corer down. This can be easier said than done on some of my land that has been reclaimed and has only a light cover of soil over shale. I zig zag across each paddock making sure to avoid taking a core on or near any dung pad or other feature that could affect the result.

Using the results

Once the results come back, I discuss them with my advisor and we work out a farm fertiliser plan. My priority is always to get the lime sorted out first, as I know from experience that I get a better response to fertiliser on the fields that are at the correct ph. After that I target my phosphorous (P) allowance onto the ground that needs it most. All of my slurry is coming from slatted tanks and most of it gets recycled back onto the silage ground that produced the slurry in the first place. Any extra slurry and soiled water I have goes on the low index fields that I can get it on to.

Clover

I intend to top seed some paddocks with clover next spring and then manage them to increase their clover content. Part of this will be to increase the potassium (K) fertiliser I will apply to them - both in the form of bag fertiliser, soiled water and slurry - while at the same time, reducing the amount of bag nitrogen to 100 units or less per acre.

Cost of soil sampling

When I consider the total cost of fertiliser I use each year, the small cost of soil sampling becomes insignificant in comparison. It ensures I am making the best use of this expensive farm input and that I am targeting it to the places I will get the most benefit from.

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