For decades, research work on grazing mixtures at Teagasc Moorepark was concentrated on ploidy (tetralploid/diploid) and variety of perennial ryegrass.
That focus has shifted in recent years with much more work going on in the area of species and their interaction with perennial ryegrass.
Clover has long been seen as the best companion species to ryegrass due to its ability to fix atmospheric nitrogen to the soil, its increased dry matter production in the sward and its benefits in terms of milk production.
The grass and clover experiment at Moorepark is now running for nine years having been established in 2012.
Over that time, just 30% of the paddocks on the farmlet study have been reseeded and average grass growth across the grass-clover treatments has been 13.5t/ha.
There are currently three treatments: grass only on 225kg N/ha, grass clover on 150kg N/ha and getting spread nitrogen after every grazing and grass-clover on 150kg N/ha but getting nitrogen at alternate times.
All three treatments are under the same management save for the amount of nitrogen being spread and the timing of application.
Researchers Deirdre Hennessy and Ellen Fitzpatrick are investigating if skipping every second application of nitrogen will have any impact on performance in one of the grass-clover treatments.
After the first week in July, the grass only treatment had grown 7.124tD M/ha, the grass-clover and regular nitrogen applications had grown 7.161t DM/ha, while the grass-clover with longer fertiliser intervals had grown 7.030t DM/ha.
In terms of milk production, the cumulative milk solids production up to 4 July was 269kg MS/cow for the cows on the grass-only treatment and 280kg MS/cow for the cows on both grass-clover treatments.
Days in milk and concentrate use were the same for all cows.
If the higher pasture growth results carry through to year-end, it’s likely that the advice will be to spread nitrogen fertiliser little and often on grass-clover swards but a full analysis will be required before any conclusions can be made.
There are two multispecies experiments going on in Moorepark currently.
Ciarán Hearn is carrying out a study looking at pasture production of various multispecies swards at differing levels of chemical nitrogen. This is being carried out in a plot study grazed by dairy cows.
In total, there are 10 different species mixtures being evaluated ranging from perennial ryegrass on its own to ryegrass, white and red clover, plantain and chicory. These are being evaluated under 0kg N/ha, 100kg N/ha, 150kg N/ha and 200kg N/ha fertiliser rate regime.
All mixtures were sown in July 2019 at a seed rate of 12kg/acre.
In 2020, across all nitrogen treatments the highest-yielding mixtures were the ones with the most varieties present with the monoculture of perennial ryegrass having the lowest yield.
Unsurprisingly, yields increased for all mixtures at the higher chemical nitrogen rates. The percentage of clover in the swards (where sown) decreased at the higher N rates.
The percentage of chicory and plantain in the swards was relatively consistent at the different N rates.
The percentage of weeds in the sward was consistent across all treatments, even the monoculture swards.
Ciarán is also looking at nitrate leaching levels from different species under different soil types using large lysimeters. These are sections of pipe filled with soil. All water that travels through the pipe is collected and analysed.
There are two soil types being examined – these are a heavy soil and a light soil. A monoculture of two species is sown in each soil type; plantain and perennial ryegrass.
Ciarán is manually applying cow urine at two different times per year to each plot to mimic what happens in a urine splash. The experiment will help to indicate if there is less nitrate leaching under plantain compared to perennial ryegrass.
The second multispecies experiment at Moorepark is at Curtins Farm and full details of this experiment were previously reported (16 June 2021). In a nutshell, this is a full-scale systems experiment comparing multispecies to grass-only and grass-clover swards.
As of 5 July, the cows grazing the multispecies swards produced 309kgMS/cow, the cows grazing grass-clover produced 293kg MS/cow, while the cows grazing grass-only produced 296kg MS/cow.
The cows grazing grass only and those grazing multispecies had the same days in milk at 132, while those on the grass-clover treatment were 129 days in milk. In terms of chemical nitrogen use, the grass-only treatment had received 138kg N/ha, while the grass-clover and multispecies had received 124kg N/ha.
Total pasture growth was similar for all three treatments at 7.3t DM/ha for the grass-only and 7.2t DM/ha for the grass-clover and multispecies treatments.
Grazing utilisation, as a trait, was introduced to the pasture profit index for the first time in 2021. This was included as a star rating for trial purposes rather than as a full economic value.
A variety with a one-star rating for utilisation has an economic value of between -€15/ha and -€9/ha.
A three-star variety is more or less neutral, while a five-star variety has an economic value of €9/ha to €16/ha.
Tomas Tubritt is carrying out the research on varietal utilisation rates using grazing cows on plots at Moorepark. He says that high post-grazing residual heights reduce grass quality and lead to more complex and costly management decisions such as topping or removing as silage and he says that some paddocks are not suitable for cutting.
Varieties with a high utilisation value will have a lower post-grazing height. There is a strong correlation between utilisation rate and digestibility of the sward.
In his plot work, cows have free rein to graze whatever varieties they prefer and will only be moved on when the post-grazing height of the control variety is grazed to target height.
The post-grazing height of all the varieties is then measured with some varieties above (poor utilisation) and more varieties below (good utilisation) the control variety post-grazing height.