Kathryn George, a CAFRE dairying adviser, looks at incorporating white clover into dairy grazing swards.
There is renewed interest in utilising white clover in grazing swards. Mixed swards of clover and perennial ryegrass have a number of potential benefits.
As clover is a legume, it has the ability to fix atmospheric nitrogen and make it available to the sward, thus reducing fertiliser inputs.
Clover also helps to maintain herbage quality and sward palatability over the summer months compared to grass-only swards.
It is also more drought resistant and will maintain forage production in a dry summer.
The benefits of clover in a grazing sward are realised from May onward as soil temperatures increase.
It is important to understand the growth phases of clover and subsequent management practices to ensure a return on investing in clover.
It will be 12-18 months before any significant nitrogen-fixing benefits of clover begin. This is due to the clover plant going through several phases during establishment.
After germination, the clover plant seedling is entirely reliant on a tap root for approximately three months.
Then the plant moves into the expansion phase, whereby it is still reliant on the tap root; however, the stolons (horizontal roots at the soil surface) are developing.
At around 12 months, post-sowing, the tap root dies, and the plant is dependent on the rooting structure from the stolons.
This is known as the clonal phase, and it is now that the plant will now be actively fixing nitrogen.
This year, the Farm Management Team at the CAFRE Dairy Unit at Greenmount Campus have incorporated clover into several paddocks on the dairy cow grazing block.
In late May this year, we selected three paddocks based on being:
- Free of weeds;
- Having a soil pH of 6.3;
- Optimal P and K status (index 2 or above).
Immediately before sowing, we mowed two paddocks for bales, and pre-moved another.
This left the base of the existing sward open to allow for light penetration and subsequent germination.
We selected Aberdai, a medium-leaved clover variety, from the recommended list.
The clover was over-sown using an Einbock seeder with the tines positioned to create minimal soil disturbance as possible. It was sown at a rate of 6kg/ha (2.5kg/acre).
Grazing management through the establishment phase is critical. The aim is to graze paddocks at lower covers of 2600 kgDM/ha to ensure the young clover seedlings are not shaded out by the grass plants.
We will maintain tight grazing residuals of 1,500 kgDM/ha to allow light to the base of the sward.
We will maintain this practice for the remainder of the grazing season, and we will apply nitrogen at only half rate (12.5 Kg/ha or 10 units N per acre) for the remainder of the season.
Successful incorporation of clover into grazing swards is part of a long-term strategy to reduce fertiliser usage on the Greenmount Dairy Unit.
It will take several years to establish clover in all the paddocks and deliver to its full potential, but the journey has begun.
If you want to discuss the potential for clover on your dairy farm, please contact your local CAFRE dairying adviser.
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