Despite grassland being quite resilient, it took a battering in summer 2018. A lot of swards have not recovered and there is long-term damage that needs putting right if swards are to regain their productivity.
Ian Misselbrook, Limagrain’s grass seeds manager, says grasses suffered from the prolonged drought.
He says: “Their system was weakened, leaving gaps where pests had freer access and they became more prone to diseases such as mildew and rusts. We’re going into this season with some very ‘patchy’ swards.
“Have a close inspection and see if there are bare patches, big gaps and moss in swards.”
He suggests farmers tug some plants out of the ground. It should be tough to pull out, but if the plants are weak and come out easily, then their roots are weakened and there may be pest infestations like nematodes, wireworms or leatherjackets.
Mr Misselbrook describes last year’s conditions as premature ageing for some swards.
“As a sward gets older, or if it has faced adverse conditions, the proportion of productive species will decrease,” he says.
“Grass varieties lose their vigour and the increasing threat of weeds will make the crop less palatable, less digestible and less responsive to fertiliser.
“A new ley should have a high rye-grass content, usually above 90 per cent. By eight years old, this could have dropped to 40 per cent, and by 10 years old it is possible that only 10 per cent of the sward will be rye-grass.”
Less productive swards will have lower energy output. AHDB Dairy data shows that a two-year-old ley yielding 13.5t/ha at 12ME will drop to 11.2t/ha and 11.5ME by year five. In year 11, yields will be almost half that of year two.
“We estimate the cost of a full reseed at around £620/ha (£250/acre), taking account of cultivations, seed, fertiliser, labour and machinery,” he adds.
“This expense will be recouped through energy from new grass leys within four years.”
Once farmers know the condition of their swards, they can decide on the required renovation or reseeding required to get their swards back on track.
“This can be done in spring, but another window of opportunity is after a silage cut when the sward is fairly open, ideally after second cut when the existing grass will be less likely to compete with the new seedlings,” Mr Misselbrook adds.
“The pasture renovation environment can be quite hostile compared with that of a reseeding environment.”
Choice of mixture will have a bearing on the success of the sward repair.
“Look at the seed choices and go for one of the more advanced mixtures now available that offer improved yield and feed values and have the data to support it,” he says.
“Paying a bit more is easy to justify. The preparation cost of a reseed or renovation is the same, so there is no point in compromising when it comes to seed mixture selection.
“And there are mixtures that have improved fibre content and digestibility and have been shown to improve milk yields and meat production.”