Clover-powered dairy performance with lower emissions

David Dolan’s dairy system in Co. Mayo proves that simplifying doesn’t mean compromising. 

The fifth-generation farmer is producing 14 tonnes of grass DM/per ha through a streamlined, grass-focused system.  

Learn why the Nuffield scholar has made clover the cornerstone of his productive, low-emissions dairy farm. 

A new direction

Returning from New Zealand, David simplified his farm in Co. Mayo, switching from pedigree Holstein to crossbred cows and focusing on producing milk from grass. As a result, the farm has seen improvements in:  

• Cow weight: Mature cows now average 550kg.
• Milk solids: 535kg per cow annually (equivalent to 5,800 litres at 9% combined butterfat and protein).
• Concentrate use: Reduced from 2 tonnes to 800kg per cow per year.  

Soil health: The foundation  

Strong yields rely on fertile soils. David tests soil twice a year, targeting pH 6.5 and phosphorus (P) and potassium (K) at index 3. 

“With nitrogen curtailed, we must maximise what we can grow. That won’t happen if soil indices aren’t correct,” he explains.  

Reseeding for resilience  

On a healthy foundation, at least 15% of the milking platform is reseeded annually, with spring reseeding preferred. Strong growth in April and May allows paddocks to be temporarily removed from rotation without affecting supply. 

David either direct drills or ploughs, depending on the soil type, though he avoids ploughing where possible. A Güttler cultivator is then used to direct seed and consolidate in one single pass. 

To reduce reliance on chemical nitrogen, the Dolans sow 4kg of clover alongside 9kg of Aber High Sugar Grass (Aber HSG) in seed mixes. This spring, 15 acres were reseeded using: 

• 4.5kg AberGain (Aber HSG tetraploid)
• 4.5kg AberChoice (Aber HSG diploid)
• 2kg AberClaret (red clover)
• 1kg AberSwan (white clover)
• 1kg AberHerald (white clover) 

The field received 30 units of 10:10:20 fertiliser at sowing and has been grazed three times since April.  

“It’s been growing 1,600kg DM every 16 days with no chemical nitrogen. We’ve used Aber HSG varieties for a while. AberGain and AberChoice give us strong spring growth and good yield when combined with clover,” says David.   

Grassland expert Diarmuid Murphy adds, “Growing AberClaret is helping the Dolans fix nitrogen and lower chemical fertiliser user, which is hugely beneficial, not just from a regulatory standpoint, but a financial one too.”  

Lowering nitrogen applications without compromise 

Around one-third of the milking platform is now in grass and clover, a shift that’s helping reduce reliance on chemical nitrogen and meet tightening environmental regulations. 

David’s nitrogen strategy balances productivity with sustainability: 

• Grass-only swards receive up to 200kg of N annually.
• Clover-rich paddocks get 40 units in early spring to kickstart growth. Then, from May onwards, the clover starts fixing nitrogen naturally.  

“April is our pinch point – cows are milking well, but grass hasn’t caught up with demand, and we want to avoid feeding silage,” explains David. 

David currently farms under a derogation allowing up to 220kg of organic N/ha, though he is mindful this could change. 

Grassland management: Grazing smarter  

By extending the grazing season to 10 months and optimising how land is used, the Dolans have reduced reliance on bought-in feed and improved overall productivity. 

To maximise utilisation, they:  

• Increased the milking platform to 44 hectares. 
• Streamlined outlying support blocks to a single 24ha-silage block. 
• Lowered the stocking rate from 4 cows/ha to 2.8.
• Contract-rear calves in their second year.
• Tightened the spring calving block to 10.5 weeks starting 10^th February.
• Rotationally graze on a 21-day cycle.  

Zero grazing and silage strategy

To support the system, the Dolans take three cuts of red clover silage and two cuts of grass annually. From October, cows are fed 17kg DM of zero-grazed red clover silage by night and graze by day, with 2-3kg of concentrate fed in the parlour. 

“A contractor does the zero grazing for us. It allows us to clean off the red clover at the end of the year and gives us a good boost in milk production,” explains David. 

Managing the transition to grazing   

This season, 90% of cows were calved within six weeks – a 30% improvement since switching to crossbreeding. After calving, cows spend two to three days indoors before moving to grass for short daily grazing.  

To start the season, cows are supplemented with red clover silage and 2-3kg of a 16% protein concentrate in the parlour. 

“This spring was exceptional. We’ve had the Rolls-Royce of a season for grass, and cows were out full-time in February,” says David. 

He adds: “We didn’t feed more than 4kg of concentrate per head. By April, grass was plentiful, and we were able to pull feed back to 2kg, which improved utilisation.” 

Breeding for efficiency

Improved utilisation has also been driven by more efficient cows. The herd’s replacement rate is 18-20%, with heifers selected based on milk recording and herd data. Ideal traits include:  

• 550kg mature weight
• Calving in the first 4.5 weeks
• 9% milk solids
• No health issues  

Looking ahead  

The farm’s last carbon audit showed emissions were 1.13kg of CO₂ equivalent per kilo of fat and energy-corrected milk. The next investment is solar panels for the milking parlour to reduce energy costs and boost sustainability.   

David completed a Nuffield Scholarship in 2022, focused on ‘Net Zero Carbon Emissions’. He believes that while farmers should do all they can to reduce emissions, it should not be at the expense of sustainability and profitability. 

“If we are to remain profitable, we need to grow 14t of grass per hectare; otherwise, we have to import more feed, and that’s achieving nothing for environmental sustainability.” 

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