Farm Ireland

Thursday 18 January 2018

Lime applications is essential to boosting returns on fertilisers

The use of lime has halved since the 1980s, despite the fact that 88pc of soils are at sub-optimum fertility.

"We used about 1.5 million tonnes annually in the 1970s and 1980s, but this has dropped to about 750,000t in the last decade," claimed grazing expert, Michael O'Donovan.

"Farmers basically gave up liming when quotas came in, but the fact is that every acre of grassland should be getting an average of 1t of lime annually," said the Teagasc specialist.

There is approximately five million acres of grassland on Irish farms.

Yet, 35,000 soil samples analysed by Teagasc over recent years show that only one in ten are at the target levels of pH, phosphorus (P) and potassium (K).

"We're losing the benefits of fertiliser and perennial ryegrasses if we don't get our pHs right. These are the invisible costs that we can't easily see on farm.

"But getting your pH right is the equivalent of an additional 60-80 units of nitrogen.

"The cost is small in comparison to other soil fertility measures at around €8/ha, compared to closer to €40/ha for P. Lime will actually increase the return from your P by 2.5 times," said Dr O'Donovan.

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He also reminded farmers at the open day not to forget to keep increasing their paddock sizes to cope with bigger herd sizes.

"Your paddocks should be 4-5pc of the grazing area, so you should only have about 20-25 paddocks on the farm. Target grazing covers should be 1,300-1,600kg/ha of drymatter (DM). Any higher, and you lose grass utilisation.


"Lower covers of 1,100kgDM per hectare force the cow to walk around for an extra 1.5 hours to get her intake," he said.

Farmers attending the event were interested to know about the economics of zero-grazing in efficient grass systems.

"Zero-grazed grass is just as expensive as first cut silage, which is about double the cost of grass grazed directly by the cow," said Dr O'Donovan.

"Before you go spending on this type of machinery you need to be certain that you have already maxed out the productivity of your milking platform and any other options you have to graze your cows.

"You cannot do this if you aren't measuring your grass on a weekly basis," he said.

The grass specialist also encouraged farmers to spend less time in their tractors topping and pre-mowing grass instead of out walking their farm and recording grass growth and covers.

"You'll be much better off spending 90 minutes out walking your farm than the same time in your tractor mowing and topping grass. Measurement is really, really crucial," added Dr O'Donovan.

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