Clover Article

By Joanne Masterson, B&T Drystock Adviser, Teagasc, Galway/Clare

With input costs increasing in 2022, this is an important year for grassland farmers to renew their emphasis on clover establishment, but combine this with improved grazing management.

White clover is the most commonly sown legume species in grassland. It fixes the nitrogen in the soil through its rhizomes in the root nodes of the plant. Nitrogen fixation is a process whereby the clover fixes N from the atmosphere and makes it available for plant growth, essentially it creates its own fertilizer.

Benefits of White Clover:

The benefits of white clover tend to occur from May onwards as sward white clover content increases. The main benefits of white clover inclusion in grass swards are:

• Increased herbage quality compared to grass-only swards in the summer months.
• Increased dry matter (DM) intake in summer and autumn.
• Higher milk production and live weight gain.
• Nitrogen fixation – white clover fixes nitrogen (N) from the atmosphere making it available for plant growth.
• Lower requirement for N fertiliser application in summer.

Impact at Farm Level:

On dairy farmers, research has shown that using clover can increase milk solids production 20-48 kg/cow per year and increase net farm profit by €108-€305/ha.  On suckler farms, profitability increased by 14% for the grass/clover system when compared to a ‘conventional’ pasture system. 

How it Works to Reduce Emissions:

Nitrous oxide is one of the 3 main greenhouse gases and is given off primarily from slurry stored, slurry spread and chemical nitrogen fertiliser spreading.  Incorporating clover into grassland reduces the demand for chemical nitrogen.  Therefore, if there is less chemical nitrogen fertiliser spread, there is less nitrous oxide being emitted into the air.  Using clover achieves a reduction in nitrous oxide by lowering the chemical N fertiliser use (up to 100 kg N/ha on dairy farms). 

Impact on the Environment:

Using clover to reduce the use of chemical nitrogen can reduce nitrous oxide emissions by up to 40% on a dairy farm due to reduced chemical N fertiliser application.  The reduction is less on drystock farms due to lower chemical nitrogen use. Clover will help to reduce the carbon footprint of farm and more importantly reduce total emissions on the farm. 

Actions Farmers Need to Take:

Over a 5 year period aim to have white clover in 100% of your paddocks (at a minimum average annual sward clover content of 20%).

4 Year Plan:

Target: 100% of the farm with 20% clover swards

Use a combination of reseeding and over-sowing

10% reseeding per year

20% oversowing per year

Year 1 – Reseed 10% & oversow 20%

Year 2 – Reseed 10% & oversow 20%

Year 3 – Reseed 10% & oversow 20%

Year 4 – Remaining 10% & any ground that clover didn’t establish on

The Plan for Achieving the Target:

Paddocks for a full reseed should be identified as early as possible in the process to avoid over-sowing clover. Take into account: poor performing paddocks, age of sward, weed content etc.

Select paddocks for over sowing to give the best chance of establishment

• Optimal soil fertility (index 3 or > for P & K, soil pH 6.5)
• High perennial ryegrass content
• Open/low density swards – dense swards prevent light getting to new clover plant, hindering establishment
• Low weed content

Any paddocks that are not suitable for oversowing in the 1st year should have any issues corrected and oversow the following year e.g. improve soil fertility, spray weeds. 

Checklist before sowing

Soil pH  6.2-6.5

Soil P   Index 3+

Soil K   Index 3+

Infrastructure Paddock system where each paddock is grazed within 3 days on an 18-21 day rotation?

Weeds   Whether oversowing or reseeding, have weeds removed before clover is established

Varieties   Large leaf varieties - silage,
Medium leaf varieties – grazing cattle,
Small leaf varieties – grazing sheep

Managing Grass/White Clover Swards:

• Graze covers every 18-21 days (9-10cm) – don’t let grass shade out white clover
• Graze 4cm all year – let light down to the stolon
• Reduce Nitrogen fertiliser applied from early may onwards (half rate)
• Reduce bloat risk – for animals accustomed to clover swards bloat is not usually an issue. But for high risk animals introduce them gradually to clover swards, don’t let them in hungry to clover swards and don’t move them from poor quality swards to clover ones. Alternatively feed roughage before grazing, graze when the clover sward is dry or use bloat oil in the water (25ml/LU/Day).

In summary, increasing the clover content in grassland can result in increased production and quality with less nitrogen fertiliser. However, care must be taken at sowing to ensure successful establishment. In the following months and years, management practices around grazing and fertiliser use must be adjusted to allow the crop to thrive.

Chloe Heanue, Student, Mountbellew Agricultural College/GMIT and Aoife Forde, Teagasc, Athenry attended the Clover Farm Walk on the farm of Kevin Moran, Caherlistrane, Co. Galway last week.