Improving Nitrogen Use Efficiency by increasing white clover content of grass swards

Rhydygofaint Farm relies entirely on grass and silage to feed their herd of 120 Holstein Friesian dairy cows, Texel cross Charollais sheep flock, and beef cattle. Nitrogen fertiliser is therefore a major input cost to address for their grass-based production.

This project investigates white clover, a legume that offers a potential solution to this challenge. With nitrogen-fixing bacteria contained in nodules on its roots, white clover captures atmospheric nitrogen and converts it into a plant-usable form through a natural process. This biological nitrogen fixation can potentially replace up to 150 kg/ha of synthetic fertiliser, leading to significant cost savings.

The benefits of white clover extend beyond cost reduction. It boasts the highest digestibility of common grassland plants and a high crude protein content, resulting in increased quality pastures for grazing animals.

Irish research provides compelling evidence. Dairy farms transitioning to clover-based swards have halved their nitrogen fertiliser use while maintaining or even increasing milk production. Notably, one project achieved national average milk output with just half the national average fertiliser input, demonstrating the power of clover.

The project will explore two approaches for maximising white clover’s potential:

• Overseeding existing swards: to compare standard white clover with a hybrid variety at different seeding rates
• Full reseeding: explore a full reseeding option, involving surface cultivation

The project will carefully monitor clover establishment, dry matter production, sward quality, and botanical composition throughout the growing season. Additionally, milk yields and quality will be tracked to assess the impact on overall production.

By closely monitoring the trial’s progress, the aim is to determine the optimal N fertiliser application rate for clover-dominant swards. This will potentially allow a reduction in costs while maintaining or increasing production.
Through driving further improvement in efficiency in these key business areas, the project will also contribute to the Sustainable Land Management outcomes including:

• Supporting improvement in maximising carbon storage and sequestration while reducing the whole-farm carbon footprint
• Clean air from less potential volatilisation of inorganic nitrogen fertiliser
• Clean water from less potential runoff of inorganic nitrogen fertiliser