'It's not a crime to put slurry on grazing ground, but there is a better option'

Kevin O Hanlon spreading slurry on his farm at Ballywilliam, Co Wexford Photo: Roger Jones
Kevin O Hanlon spreading slurry on his farm at Ballywilliam, Co Wexford Photo: Roger Jones
Ciaran Moran

Ciaran Moran

Slurry is an extremely valuable source of nutrients on livestock farms and farmers must make the most of it, according to respected fertiliser specialist Stan Lalor.

The former Teagasc researcher who now works for GrasslandAgro told farmers at a recent farmwalk in Clare that 1000 gallons of thick cattle slurry is worth the equivalent of a 50kg bag of 5-5-30.

"When you consider your slurry as a bag of fertiliser you start to put a value on it.

"Most livestock farmers have a tank of slurry that is sitting there its produced by the cows over the winter and contains a lot of nutrients those nutrients are potentially valuable.

However, he warned that 'watery slurry' doesn't have the same horsepower in terms of NPK.

"Farmers need to be aware that 1000 gallons of material that is 50pc slurry and 50pc water is only going to be 5-2.5-15. So you will need to adjust your slurry application rates up a bit if you are producing this type of slurry."


Lalor noted that slurry was a particularly valuable commodity on farm when it comes to maintaining the soil fertility of silage ground.

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"If you think of the P and K levels on slurry at 5units of P and 30units of K.

The ratio there is about 1:6 which is very close to the ratio to the ratio required for a silage crop," he said.

He highlighted that to grow a tonne of grass for silage or grazing requires the same amount of nutrients out of the ground.

However, he stressed that the difference when you cut it for silage is you take all of the grass out of the field.

"When a cow grazes a paddock she leaves a lot of P and K after her as she is grazing.

"But with a baler or a silage trailer, you take it all out of the filed. You remove particularly a lot of K in a silage crop," he said.

"It's not a crime to but slurry on grazing ground. However, if you have slurry going on grazing ground you have pulled a lot of nutrients particularly potassium away from silage fields.

"If you don't do something to get that potassium back on the silage ground you will run down the fertility of the soil, he said.

Larlor said that it is his experience that often farmers find win their soil test results that the fields that were high particularly for K are close to the yard and getting a lot more slurry than others.

"The fields that are often low in K are those farther away and might be used a lot for silage.

"All other things being equal slurry and silage are well matched," he said.

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