Farm Ireland

Friday 22 September 2017

Sorting out your Ps and Ks

Soil fertility remains a key issue on many farms with over 90pc of soil samples analysed by Teagasc last year deficient in phosphorus (P), potassium (K) or lime.

"For every tonne of grass you grow on your farm per hectare and utilise it is worth €100 net VAT in your back pocket. That is a very important figure," explained James Keane, as he pointed out around 14t/DM a hectare is being grown on the Grange farm.

"On average farmers are growing about 7t/DM/ha if we can even get from 7t to 10t/DM/ha we are going up by 3t/DM and we are going to put another €300 a hectare in our pocket at the end of the day," he said.

"Lime is hugely important - to take a soil from an index one to an index two it takes exactly €100 an acre. To bring it up another index it takes €100 an acre," he said. "Get the lime right before you sort out the P and the K.

Ned Heffernan, an advisor at Teagasc Grange, said that poor pH levels must be addressed first, with granulated lime more of a "quick fix" solution and ground lime a more longer-term option that delivers the most per cost over time.


It was also pointed out that after liming in areas of high-molybdenum soils it may be necessary to administer copper to animals as it can lock up the element.

"If your pH isn't right you can't expect soil to perform," he said, with optimum levels at around 6.5.

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Farmers were advised to avoid spreading urea on ground that has been limed for three to four months, however, slurry can be spread but there may be some loss of nitrogen.

It was highlighted that silage ground should be cut before lime is spread as it can impact on preservation in silage pits.

Mr Heffernan said some farmers say they find urea doesn't work as well as CAN yet research shows it delivers the same response.

"On a cost basis if you take your tonne of CAN and your tonne of urea at the moment - your tonne of urea is nearly a third cheaper than your tonne of CAN and it is going to give you the same response especially at this time of the year," he said.

He added that 48 hours of dry weather was needed after spreading but urea did need 10-15ml of rain to wash it in.

Indo Farming