Only 25% of farmers recording grass measurements on PastureBase are grazing at the correct covers.
This is the conclusion of Moorepark researcher Michael O’Donovan, who was speaking at the Teagasc virtual dairy conference last week.
The PastureBase data suggests that the average pre-grazing yield during the mid-season is 1,669kg DM/ha, with just 25% in the optimum category of 1,400kg to 1,600kg DM/ha pre-grazing yield range.
Most pre-grazing yields (35%) are in the 1,600kg to 1,800kg range, while 19% are in the 1,800kg to 2,000kg range, with a further 10% of pre-grazing yields between 2,000kg and 2,500kg.
Similarly, 11% of pre-grazing covers are too low, at between 800kg and 1,400kg DM/ha.
There is a difference of almost 4t DM/ha between the top 25% and the bottom 25% of farms on PastureBase in terms of annual grass production.
Michael believes the mid-season period is where a lot of this difference is coming from, with high pre-grazing yields reducing the number of grazing events and reducing growth rates.
The crucial thing for us is there are huge efficiencies from a grazing management perspective
“Can we drive better decisions mid-season and what can that do for us? Rotation length, which is something all farmers are responsible for, is probably too long. We might think we’re on a shorter rotation but, by default, we’re probably on a longer rotation.
“The crucial thing for us is there are huge efficiencies from a grazing management perspective but also from a carbon perspective and milk production perspective by slightly dropping our pre-grazing yields mid-season.”
He goes on to say that achieving the target pre-grazing yields of 1,400kg to 1,600kg is better for the cow as it assures more consistent intake and higher milk solids yield.
Grazing at 1,400kg increases grass quality, allows for faster regrowth, increased grass utilisation and does away with the need for topping.
In terms of carbon emissions, he says there is significantly lower methane emissions from grazing lower pre-grazing yields compared to higher pre-grazing yields.
Management of clover featured heavily throughout the online event. Researcher Brian McCarthy gave an update on the clover study at Clonakilty.
The first clover experiment there ran from 2014 to 2017 on swards reseeded in 2013.
By 2018, there was just 10% clover content remaining on these swards, which had been receiving 250kg of chemical nitrogen per hectare per year.
An intensive reseeding programme commenced with 20% and 15% of the farm reseeded in 2019 and 2020, respectively, plus 20% of the farm was over-sown with clover per annum.
This strategy has been successful and clover content increased from 13.8% in 2019 to 19.4% in 2021 on average across all paddocks in the clover treatments.
The current study is looking at grass-only and grass-plus-clover swards under two nitrogen treatments; one with 250kg N/ha and the other with 150kg N/ha. The stocking rate is 2.75 cows/ha.
The grass-only and 250kg N/ha grew 15.2tDM/ha and produced 68% of the herd’s winter feed requirements
Brian says that each treatment is given the same level of nitrogen up to late April and then the clover treatments receive less chemical nitrogen than the grass-only treatments.
From 2019 to 2021, the grass-only swards with 150kg N/ha grew an average of 13.8tDM/ha and produced just 45% of the winter feed requirements.
The grass-only and 250kg N/ha grew 15.2tDM/ha and produced 68% of the herd’s winter feed requirements.
By contrast, the grass and clover swards with 150kg N/ha grew 14.6tDM/ha and produced 56% of winter feed requirements, while the grass and clover swards with 250kg N/ha grew 15.7tDM/ha and produced 72% of their winter feed requirements.
Brian says that on the 150kg N treatment, the clover is making an impact with grass yield in between the grass only 150kg and 250kg nitrogen treatments but that the clover contents were probably not sufficient to bridge the gap entirely.
“In terms of winter feed, it’s fair to say that we didn’t make enough winter feed on any of the systems and our stocking rate is probably too high at 2.75 cows/ha for the amount of grass we grew over that three-year period.
“In particular, we didn’t make enough winter feed on the low nitrogen treatments and the grass-only 150kg especially due to the fact that we didn’t make as much silage during the summer and also we had to feed back extra silage to build grass covers in the autumn,” Brian says.
The cows on grass only produced an average of 466kg MS/cow
In terms of milk solids, there is a 29kg MS/cow difference between the grass-only and grass-plus-clover swards on average over the three years of the study.
The cows on grass only produced an average of 466kg MS/cow, while those on the grass and clover treatments produced 495kg MS/cow on average.
Offaly farmer Ger Pardy, who is milking 280 cows with his wife Margaret near Birr, spoke about his experiences with clover.
Ger says he was attracted to clover initially for the milk solids benefits but is now using clover to reduce nitrogen usage which is both helping the environment and reducing the cost of production.
Unlike a lot of farmers, Ger has found oversowing to be successful on his farm and has historically struggled to keep clover in reseeds. However, he says that his management of reseeds was to blame, as he used to let covers get too strong which shaded out the clover and spread too much nitrogen on reseeded fields allowing the grass to over-power the clover.
At this stage, all of the Pardy farm has some clover but 40% of the farm has what Ger describes as good clover and this area gets less chemical nitrogen.
Last year, he spread 10 units/acre of nitrogen on this area during the main grazing season after each grazing, but plans to spread little or no chemical nitrogen on this area next season.
Instead, he will spread this area with slurry in spring and chemical potash after every second round of grazing.
The low rate of nitrogen last season worked very well and he says these paddocks never looked pale and they grew as much or more than the rest of the farm.
The Pardys grow an average of 15tDM/ha and the milking platform is stocked at 3.5 cows/ha.
In relation to clover-safe sprays for next season, Michael O’Donovan says he expects that a derogation for clover-safe sprays will be available next season.