A huge topic of discussion at Moorepark ’25 open day was laying down strategies to grow 15t dry matter (DM)/ha, and grass clover swards was highlighted as being one of the main measures to do this sustainably.
The discussions around grass clover swards has been around for quite some time now and it is fair to say that many farmers grew frustrated with the legume last due to its inability to persist in swards amid poor weather conditions.
However, at Moorepark ’25, there was a massive focus on the importance of having a high clover content in swards to deliver extra milk solids while decreasing nitrogen (N) application.
While perennial ryegrass (PRG)-only swards have the potential to grow 13-14t DM/ha in the right conditions, they have a very high dependence on chemical N application.
The most recent clover experiment at Moorepark shows the effects of white clover inclusion in PRG swards on the performance and profitability of spring-calving dairy systems.
Grass-clover swards
A Teagasc study examined three treatments: PRG only sward receiving 200kg N/ha (Gr200); PRG-white clover sward receiving 150kg N/ha (Cl150); and a PRG-white clover sward receiving 100kg N/ha (Cl100).
There was 20 cows per treatment and each treatment was stocked at 2.4cows/ha.
Cows were assigned to treatment based on calving date, parity, pre-experimental milk yield and economic breeding index (EBI) and stayed in the treatment for the entire lactation.
Treatments were rotationally grazed from early February to mid-November and target post-grazing sward height was 4cm.
The nitrogen fetiliser strategy throughout the year and throughout the eight rotations were as follows:
Rotation/date
Gr200
Cl150
Cl100
February
28
28
28
Mid-March
28
28
19
April 15 (2nd rot)
20
20
19
May 6 (3rd rot)
20
13
9
May 27 (4th rot)
17
9
0
June 17 (5th rot)
17
9
0
July 8 (6th rot)
17
9
0
July 29 (7th rot)
17
9
0
August 19 (8th rot)
17
9
9
Mid-September
19
16
16
Total
200kg
150kg
100kg
The study found that cows grazing the grass white clover swards with 20% white clover content had a higher milk yield of +230kg of milk per cow.
Milk solids yield was increased by 32kg per cow compared to cows only grazing grass only swards.
The difference in milk solids production between the PRG only and PRG-WC treatments occurred due to higher milk yield produced rather than a difference in fat or protein content.
The full breakdown of the sward types effect on milk performance and herbage production is as follows:
Gr200
Cl150
Cl100
N fertiliser spread (kg/ha)
200
150
100
Grass production (t DM/ha)
13.8
13.6
13.5
Clover content (%)
0
19.8
20.1
Silage made (kg DM/cow)
1,079
1,054
1,050
Silage fed during lactation (kg DM/cow)
460
475
497
Concentrate (kg/cow)
716
714
710
Milk yield (kg/cow)
5,650
5,881
5,878
Fat content (%)
5.16
5.30
5.36
Protein content (%)
3.70
3.73
3.76
Milk solids yield (kg/cow)
504
534
537
Farm gate N use efficiency (%)
37
48
64
Farm gate N surplus (kg/ha)
156
104
54
So how did these results affect the bottom line?
The cost of N fertiliser per treatment, including silage, was €1.04kg N applied and €210 per tonne of silage fed.
Milk solids were included at €5.09kg of milk solids based on a milk price of 36c/L.
Compared to the PRG-only sward, both white clover treatments had increased profit of +€445/ha for Cl150 treatment and +€563/ha for the Cl100 treatment.
The reduction in fertiliser application to the Cl100 treatment resulted in an increased farm profit of €118/ha compared to the Cl150.
This study proves that 20% clover content and PRG swards allow farmers to significantly reduce their fertiliser application while maintaining or increasing production and significantly increasing profits in a sustainable manner.
If farmers are looking to drive on grass performance, more incorporation of clover is a step in the right direction to utilising more herbage in your system, reducing costs, and potentially reducing your concentrate supplementation reliance.
