Researchers at Teagasc Moorepark have been looking at individual grass varieties on commercial dairy farms since 2013. The results from these on-farm evaluations allow farmers and researchers to get a better handle on how a variety will perform on a commercial farm. While the on-farm evaluation work is not yet feeding into pasture profit index (PPI), it is useful information for farmers when choosing a grass variety to sow on their farm.

According to Michael O’Donovan, grassland researcher at Moorepark, the correlation between the PPI and the on-farm evaluation for dry matter yield is 0.77, which means the two are closely connected. So a variety that has a high PPI for yield will perform well in the on-farm study and vice versa. “We have seven years of data from the monoculture on-farm study, looking at 22 varieties on 104 farms across Ireland. Over the seven years, the top-yielding variety grew 10t/ha more than the lowest-yielding variety, which is worth €128/ha/year. The on-farm work verifies that the PPI is working, so it’s very important information and something we will continue to do,” O’Donovan says.

Monocultures of perennial ryegrass varieties are sown in full paddocks on commercial dairy farms and the farmers manage the field like any other. Grass growth, the number of grazings and silage cuts are recorded through PastureBase. The fields are scored for post-grazing height and ground by Teagasc personnel at various times throughout the year.

Over the seven years, the standout performer, from a grass yield point of view was Abergain, recording an average dry matter yield of 14.7tDM/ha over the seven years (see Figure 1).

There are four varieties beneath Abergain which all achieved similar levels of yield at around 13.9tDM/ha. These are Dunluce, Drumbo, Astonenergy and Abermagic. The lowest-yielding varieties were Tyrella and Glenveagh, at around 13.2tDM/ha each.

As new varieties go on the recommended lists, they are evaluated in the on-farm study (see Figure 2).

Some of these newer varieties are outperforming older varieties such as Abergain.

Of the newer varieties, Aberclyde and Aberplentiful are the two highest performers, recording mean yields of 15.1t/ha and 14.8t/ha, respectively, over the three years from 2017 to 2019, outperforming Abergain which yielded 14.7t/ha. However, it remains to be seen whether the newer varieties performed better because they are genetically superior, or because they were more recently sown.

Grazing

One thing the researchers at Moorepark are adamant about is the importance of grazing as a trait to evaluate. Some varieties are grazed more often than others. This is an important measure, because it shows that, firstly, the variety needs to be growing a lot to be grazed more frequently and, secondly, it shows that the variety is producing good-quality grass. To put it another way, varieties that are not grazed very often are not grazed often for a reason. Either they are not growing enough or they get stemmy too quickly and are then skipped over for silage.

According to O’Donovan, the minimum number of times a variety should be grazed in a year is seven. Eight of the 11 varieties analysed over seven years had a mean number of grazings greater than seven (see Figure 3).

Three varieties – Astonenergy, Abermagic and Kintyre – were grazed on average 7.4 times, followed by Abergain at 7.3 grazings on average.

Of interest are the varieties that were grazed least; Dunluce, Glenveagh and Tymax achieved 6.5, 6.6 and 6.8 grazings per year on average, respectively. Glenveagh and Dunluce both fare badly when the mean grazed yield is looked at over the seven years. They have a mean grazed yield of 10.6t/ha and 10.7t/ha, respectively, compared with over 12t/ha for Astonenergy, Abergain and Abermagic. This is despite the fact that Dunluce is a high-yielding variety, but a lot of that yield obviously went towards silage and not grazing.

Abergain, a tetraploid perennial ryegrass variety performs well in the monoculture study.

In my view, this tells us that varieties such as Glenveagh and Dunluce are not suitable for a high-performing grazing system.

Ground score

The interesting thing is that Abergain (tetraploid) has the same mean ground score as Glenveagh (diploid). Mean ground score was calculated based on six years of data from 2013 to 2018. These two varieties had the highest ground score of the 11 varieties measured at 4.1 each. Indeed, Abergain was the most consistent of all varieties in terms of ground score. In 2013, it had a ground score of 4.5 falling to 4.1 in 2018 – the highest of all varieties evaluated. Contrast that to Glenveagh, which had a ground score of 5.3 in 2013 but this was down to 3.5 in 2018. This indicates good persistency with Abergain.