This year’s Irish Grassland Association summer dairy tour was held on two heavy soil farms on the Cork/Kerry border.

Sean O’Riordan farms 80ha near Kiskeam in north Cork. He has a 40ha grazing platform, split by two roads and is milking 100 cows at 500ft to 800ft above sea level on heavy clay-type soil.

Farming on heavy soils is one thing, but farming in a high rainfall area compounds the problems. The annual rainfall recorded in 2015 was 2m (79in), which is almost three times the amount of rainfall at the Greenfield farm in Kilkenny.

Stocking rate on the milking platform is 2.5 cows/ha and grass grown in 2015 was 10.6t/ha. Three out-farms provide grazing for replacements and silage for the herd. This year, Sean has 17 in-calf heifers and 35 heifer calves. Sean is milking in a 12-unit parlour built in 2002 and he has slatted wintering facilities for 104 cows.

The herd has evolved from a British Friesian background to a high EBI Friesian Jersey cross herd since 2010. Herd EBI now is averaging €178 (€51 milk/€93 fertility).

Performance from the herd is very good, but Sean plans to increase the stocking rate and improve performance further. In 2015, the average stocking rate was 2.5 cows/ha with milk solids of 1,004 kg/ha delivered on meal fed of 680kg per cow and grazed grass. Fertility is good with a six-week calving rate at 84% and an empty rate of 6%.

Sean’s target is to stock the farm at three cows/ha and produce 1,350kg MS/ha feeding similar meal per cow at 650kg. Sean’s idea is to have an invisible, medium-sized cow delivering good milk solids and high fertility, which is easy to maintain on condition score. Mostly Jersey and Jersey crossbred bulls have been used for the past two seasons.

Drainage plan

Sean is part of the Teagasc heavy soils programme and has carried out some shallow drainage as part of the trial. The difference has been enormous with production from the drained fields increasing from 6.8t/ha in 2011 and 2012 to 11.25t/ha in 2014 and 2015. The field was drained in 2013.

Despite the drainage costing €3,240/ha, Sean maintains it will pay for itself in about five years. The difference in growth is 4.45t of dry matter. Assuming an 80% utilisation rateof that extra grass and a value of €200/t DM utilised, the extra grass is worth about €700/ha.

The method of drainage used was shallow drains, 1.1m deep, placed across the field at 15m intervals with the field sub-soiled at opposite direction to the drains. Teagasc drainage specialist Pat Tuohy warned farmers not to get hung up about the drainage method used by Sean as each site is different, so what worked in Sean’s field may not work elsewhere.

Both Sean and the host farmer in the afternoon session, Conor Creedon, put huge emphasis on soil fertility and were very critical of the current nitrates legislation, which is restricting the amount of chemical phosphorus (P) that can be applied.

Because of the heavy clay content in their soils, up to 40% of the additional P being applied is being locked up in the soil and not available for plant growth.

Neither Conor nor Sean’s farms were at optimum level of soil fertility but at least they know where they are at and have a plan for addressing the deficiencies. The average pH on Sean’s farm is 6.17, up from 5.77 in 2015. An extra 2t/ha of grass is being grown on the paddocks that were at pH 5.77. Sean spreads 2t/acre of lime on the low pH fields. Because the buffering capacity of the soils is low, the response to lime is high.

On phosphorus, only 8% of Sean’s farm is at optimum level, above index 3. He is spreading 40kg of P/ha on average across the farm, yet the P levels from his annual soil sampling are showing a decline. Interestingly, there was very little mention of soil indexes at the farm walks. All the soil fertility figures were presented as mg/l. For example, Index 3 is a P level of between 5mg/l and 8mg/l.

Sean’s future plans are to increase the amount of grass grown to 12.5t/ha, on average, but to do this he needs to get all of the farm up to index 3, get the average pH to 6.3, reseed 10% of the farm per year and drain another 8ha.

  • The Irish Grassland Association summer walk focused on heavy soils.
  • Need to correct soil fertility if going to grow more grass.
  • Start by soil sampling, then correcting pH, then P and K.
  • Sean O’Riordan grew 10.6t/ha in 2015. His target is 12.5t/ha.