How much P and K needs to be applied on suckler-to-beef farms?

Drought conditions halted both grass growth and fertiliser spreading over recent weeks. However, now that the rain has arrived, attention is turning back to fertiliser applications.

Of the drystock farm soil samples analysed by Teagasc in 2017, only 10% had optimal soil fertility levels for soil pH, P (phosphorous) and K (potassium).

At this summer’s BEEF 2018 event, Teagasc’s Mark Plunkett outlined how much P and K is needed on beef farms. He also highlighted which fertiliser is the best value for money and at what rate it should be applied.

“There is very little P and K needed on a drystock farm; the off-take is very small compared to a dairy farm,” he said.

Looking at a suckler-to-beef farm that’s stocked at 2LU/ha, he explained that there are only 7un of P and 10un of K leaving that farm in terms of liveweight.

Image source: Shane Casey

“A fertiliser like 18-6-12 is the best fertiliser on a drystock farm; farmers cannot go too far wrong with it. A bag [per acre] will maintain what is leaving in liveweight on a farm that is stocked at 2LU/ha.

“In Ireland, the majority of our soils are at Index 1 and Index 2. Therefore, three – possibly four – bags of 18-6-12 are required on intensively-stocked beef farms; that’s what we need to grow grass.

“This fertiliser will also give the right balance of N (nitrogen), P and K. Four bags will give nearly 80un of N and it will give all of the P and K required on a highly-stocked farm,” he added.

Source: Teagasc

Silage ground

Mark highlighted that on silage ground – where slurry is unavailable – three bags of 0-7-30 and three bags of CAN (calcium ammonium nitrate) are required for first-cut silage.

“That’s what you need to grow a crop of grass silage; that’s the amount of P and K leaving in the silage trailers – approximately 20un of P and 90un of K – and farmers need approximately 80un of N plus sulphur.

“If 3,000 gallons of slurry per acre is available, farmers are looking at 24-2.5-10 at a rate of three bags per acre or 27-2.5-5 at three bags per acre,” he explained.

When it comes to reseeding, Mark advised that farmers go with 10-10-20 or 0-10-20. He also advised that it be spread at a rate of three bags per acre.