How reseeding swards helps boost grassland performance

Introducing clover and herbs at reseeding provides a useful boost in dry matter content while reducing the need for purchased fertiliser, suggests a study.

Carried out by ProCam’s Field Options division, the study shows that including herbage seeds can improve the drought tolerance of grassland leys – with the added diversity making leys eligible for countryside stewardship payments.

Although bagged fertiliser prices have come down since the highs of 2022, there has still been a continued resurgence in interest among livestock farmers looking to reintroduce nitrogen-fixing clover into their grassland rotations, says Simon Montgomery, of Field Options.

But to achieve good rates of germination and establishment, the introduction of new seedstock must be done at the correct timing, with evidence suggesting that the best results are achieved when clover and herbage seeds are drilled as part of a planned reseeding programme.

Seed mixtures

Introduced at seeding, red clover, white clover, and herbs such as plantain and chicory can significantly improve the protein content and dry matter (DM) yield of forage – even when provided with modest levels of bagged nitrogen.

This response is even more dramatic when the same mixtures are managed without nitrogen, reveal trials carried out by Field Options at the Crop and Environment Research Centre (CERC)  at Harper Adams University in Shropshire.

“The objective of the CERC trial was to test the performance of a selection of grassland mixtures, with grass and clover blends being compared to leading hybrid and perennial ryegrass controls,” says Mr Montgomery.

With four years of data captured, the trial has shown that the inclusion of white clover elevates dry matter production by 0.8t/ha/year for swards receiving 250kg/ha of synthetic nitrogen, while the addition of red and white clover gives an uplift of 0.8-2.5 tonnes per year.

In both cases, the gains can easily be translated into money savings on bought-in feed and improvements in milk and meat productivity.” The trial also tested the yield response of the same mixtures when zero supplemental nitrogen was applied.

“Although some of the grass and clover mixtures struggled to perform in the first year, they subsequently went on to outyield the leading perennial ryegrass blend which had received 250 kg/hectare of N,” says Mr Montgomery.

Clover drove most of this yield boost, with white clover contributing more than 4t/ha of dry matter (DM) annually, and red clover delivering more than 5.5t/ha. Several of the mixtures tested also contained drought tolerant grasses or Boston plantain and Puna II chicory.

“The addition of these species further increased the yield response of the seed mixtures, especially in the dry season of 2020.”

This performance boost can be accounted for by the deep rooting growth habit of these species which makes them more resilient to drought by enabling them to scavenge nutrients and moisture from deeper soils.

Changing weather

“With normal weather patterns becoming increasingly unreliable, and early summer droughts more commonplace, livestock producers should give careful thought to the composition and make-up of their grass swards,” says Mr Montgomery.

This will safeguard against future weather-related pressures while enhancing overall productivity and forage quality, he adds.

“Including clovers and herbs in grassland leys can also unlock GS4 Countryside Stewardship payments and – in mixed farming rotations – improve soil structure and fertility for the following arable crop.”

But any nitrogen fixed by clover won’t immediately be available for uptake by companion grasses. This is because clover only generates nitrogen for its own use in the first 9-12 months of its lifecycle.