Herbal leys need fertiliser for best results
A new grass trial drilled in autumn 2023 at new DLF demonstration grounds near Pershore in Worcestershire, reveals some secrets of managing successful herbal leys. Sara Gregson reports
Global grass breeding company DLF has run a plant breeding, trialling and evaluation centre at Didbrook in Gloucestershire for more than fifty years, but last year moved them to a 57-hectare (140 acre) site at Pinvin, closer to their UK headquarters at Inkberrow.
Last autumn, a block measuring 55m by 25m was drilled with 15 varieties of grasses including early to late perennial, hybrid and Italian ryegrasses, festuloliums and other species including fescues, timothy and cocksfoot.
These were cross drilled at a 90-degree angle to the grass with individual legumes and herbs to investigate the interaction between the different species under a 250kg N and no fertiliser regimes.
The legumes included a selection of different sized white clovers, a red clover blend and Relish, a new red clover which has been grazed successfully in New Zealand.
The herbs on trial were Ecotain (plantain), Choice chicory, birdsfoot trefoil, Luzelle lucerne and sainfoin. There were also full herbal ley mixtures with white and red clover with AgritaiN, and one with the clovers, AgritaiN and chicory.
“The soil at the site is heavy, silty clay and can lie wet in winter,” comments Monty White, DLF agricultural project manager for the UK.
“It was interesting that the legumes and herbs did not establish well with the faster growing Italian and hybrid ryegrasses and festuloliums, because these were so competitive in early growth. They shaded the broad-leaved plants out. If farmers are just looking for a lot of early feed, these are the species to go for.
“With the slower-growing grasses, such as tall fescue, meadow fescue, timothy and cocksfoot, the herbs and legumes established well.”
Half the grid received 80kg of nitrogen fertiliser in early spring and then 30kg after each cut, which mimicked a grazing regime.
Platemeter yields were then taken on 24 July, 19 days post cutting. This provided a snapshot of nearly three weeks summer regrowth.(Table 1).
Table 1: Cross drilled plate meter measurements taken 24 July 2024
As to be expected, there was a significant difference in yield between the fertilised half of the trial and the non-fertilised half. For example, the perennial ryegrass (PRG) on its own with fertiliser yielded 154% of the untreated PRG.
More interesting results come from where the white and red clover species were cross drilled. Perennial ryegrass and white clover with no fertiliser yielded 90% of the PRG on its own with fertiliser. The small deficit in yield of 364 kg DM/ha came without the cost of buying and applying any artificial nitrogen.
The PRG with Relish red clover and no fertiliser was similar, yielding 88% of the PRG only with fertiliser.
“It was clear to see the rows which had red clover in them – they looked a lot greener, meaning there was a lot of nitrogen fixation going on,” says Monty.
The chicory and plantain results highlight the fact that they are both hungry for nitrogen to perform well, whether that comes from a fertiliser source or from legumes.
“There is a general feeling amongst farmers that herbal leys do not need fertilising – leaving it all to the legume component to feed the crop. This is compounded by elements of SAM3 of the Sustainable Farming Initiative (SFI) specifying a nitrogen fertiliser limit of 40kg/ha.
“But it is important to have 30 to 40% of a mixture of legumes, white and red clovers, in the field to keep the chicory productive.”
PRG and chicory and fertiliser came top of the yield table at 3,524 kg Dry Matter (DM/ha), closely followed by PRG AgritaiN and clover with fertiliser, yielding 3,412 kg DM/ha.
“This trial plot highlights the importance of perennial ryegrass to provide high yields of high-quality feed,” says Monty. “But also highlights the benefits of having enough and the right type of legumes to feed the system.
“Farmers buying an off-the-shelf herbal ley with 5% white clover and a little bit of lucerne will be disappointed with the growth if they do not apply fertiliser, particularly in early spring. A herbal ley has to have a good content of red and white clover to reduce the requirement for artificial nitrogen.
“As soon as the soils warm up, the clovers will get going and the bacteria in the soil will start breaking down the nodules on the roots, giving a big boost of nitrogen. This means less fertiliser will be needed over the summer.”