Soil fertility: ‘The most important thing is actually the soil test itself’

David Kerr from Ballyfin, Co. Laois, recently took part in the Irish Grassland Association (IGA) Dairy Summer Tour live discussion.

In 2014, when the tour was held on the farm, he was milking 140 cows on 64ha. In the intervening years, David has moved to 150 cows, with all replacements contract reared in Co. Kilkenny.

During the discussion, David noted that he had experienced a “fairly significant” soil fertility issue in 2014 – which he has since resolved.

Commenting on how he went about this, he said: “The most important thing is actually the soil test itself. You can deplete soil fertility very quickly and it takes a long time to regain it.

“You have to be testing every two years really when you get into that situation, and I went every year for the first three years,” he added.

“Building takes time under the current regulations; we start following the cows with a silage compound for a couple of years.

“Fields that are significantly low in potassium (K), we target them with potash. We limed one-third of the farm per year and it’s taken the guts of five years to get to where we are,” the Laois man explained.

“One of the biggest changes I have seen in grassland management – in my time – is that bales have now replaced topping as a form of grassland management.

“The unfortunate thing about bales is if you don’t keep track of where they were taken, those paddocks take a hit [in soil fertility] fairly quickly,” he said.

Contractor use

David uses the services of contractors to spread slurry or dairy washings on his paddocks to boost soil fertility.

“We are very lucky with the low emission spreading that once a field is taken out for bales, we get onto that field with dairy washing / slurry as quickly as possible. That’s putting a balance on the thing where what we’re taking off, we are putting back on.

“I have one contractor who spreads with an umbilical system in the spring which empties our lagoon with a dribble bar and then another guy who has a tanker with a trailing shoe who empties the tank of dairy washings / slurry – depending on the rainfall really.

“He goes onto those paddocks that have been taken out for bales and he can spread on any cover; cows can get in there again and graze within three or four days,” David said.

David also highlighted that building soil fertility can be slow and expensive, and even frustrating at times.

“It was frustrating as you think this thing is going to be solved fairly quickly and it’s expensive as well. You’re putting capital fertiliser into the place and there is some change when you actually have the problems solved and you go back to maintenance fertiliser.

“It takes a long time to get it up and there is a significant cost; there was a lot of money invested in soil fertility and it was a very important investment,” he noted.