Diversify grassland swards at reseeding to offset N & boost DM

Diversify grassland swards at reseeding to offset N & boost DM3 July 2023

Trials carried out by ProCam’s Field Options division have shown that introducing clover and herbs at reseeding not only reduces the need for purchased fertiliser, but also gives grassland swards a useful boost in dry matter yield. The same study has also shown that including herbage seeds can improve the drought tolerance of grassland leys, with the added diversity they provide making leys eligible for current countryside stewardship schemes.

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

“However, 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.”

Trials carried out by Field Options at the Crop and Environment Research Centre (CERC) at Harper Adams University in Shropshire have demonstrated that red clover, white clover, and herbs such as plantain and chicory, introduced at seeding, can significantly improve the protein content and DM (dry matter) 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.

“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,” Simon continues.

“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 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,” Simon explains. “The addition of clover clearly drove the majority of this yield boost, with white clover contributing more than four tonnes of DM per hectare per year, and red clover delivering more than 5.5 tonnes.”

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,” Simon continues. “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 soil horizons.

“With ‘normal’ weather patterns becoming increasingly unreliable, and early summer droughts more commonplace, livestock producers should therefore give careful thought to the composition and make-up of their grass swards – not only to enhance overall productivity and forage quality, but also to safeguard against future weather-related pressures.

“The inclusion of clovers and herbs in grassland leys can also unlock GS4 Countryside Stewardship payments in England and GFTE payments in Wales and, in mixed farming rotations, improve soil structure and fertility for the following arable crop,” Simon adds. However, he caveats this advice by reminding growers that any nitrogen fixed by clover won’t immediately be available for uptake by companion grasses, as clover only generates N for its own use in the first 9-12 months of its lifecycle. “The addition of clover should therefore form part of a longer-term nutrient and sward management strategy,” he explains.

“It’s also worth remembering that over-seeding clover into an existing sward can be challenging, with good establishment often hard to guarantee. A better option is to introduce clover as part of a reseeding strategy, although it may be necessary to control perennial weeds in the previous sward and to modify the cropping strategy by introducing a ‘cleaning’ break crop. Overall, however, it works out cheaper to sow a complete mixture of grasses and clover plus herbs in one hit compared to carrying out two separate seeding operations to introduce the components individually,” Simon concludes.

ProCam representatives will attending the British Grassland Society’s summer meeting (North Wales, 26th to 28th June) and at The Groundswell Festival (Hertfordshire, 28th & 29th June) to offer specific reseeding and grass sward management advice. Alternatively, for more information please contact Field Options on 01544 262500 or via email at info@field-options.co.uk