10 May 2002

Reseeding a risk on organic swards

Grass management on

organic livestock units is

more crucial than

conventional ones. A

recent course for producers

aimed to overcome some of

the complex restrictions.

John Burns reports

THINK long and hard before using reseeding to improve per-manent grassland, says organic milk producer Oliver Watson.

Leading a farm walk at a Soil Association organic grassland management course held at his Riverford Farm, Staverton, south Devon, he advised carefully quantifying reseedings benefits.

"The improvement may be only marginal and the sward will revert again in most cases. And remember you will sacrifice some environmental benefit by reseeding and environmental factors are part of the organic product."

Reseeding must show significant benefits to compensate for not only the cost – which would rocket when 100% organic seed had to be used – but also the risk of failure, he said. "It is hard to find a feed cheaper/t of dry matter than a field of grass you do nothing to except cut the hedges every third year, and permanent grassland is less vulnerable to poaching than a new reseed. We keep cows out from March to November and youngstock are out from March to January, so poaching is a concern."

Mr Watson also referred to the way new leys reverted and went through a period of lower productivity than before the reseed. His preferred approach was to rent more land. "It is easier to get 10% more land than to improve grassland productivity by 10% and it is certainly more reliable. Overstocking can be devastating for an organic system. For organic dairying you have to have a big pile of silage."

His only reseeding follows production of organic vegetables, an enterprise run by his brother.

Nevertheless, he warned course members to watch for the downward spiral of productivity which could occur in long term grassland and expressed interest in other ways of improving its productivity.

Alan Hopkins from the Institute of Grassland and Environmental Research, North Wyke, gave delegates some advice on oversowing existing swards with clover or grasses.

"Mow, then graze hard then oversow, ideally using one of the specialist machines. Avoid spring sowing because the existing sward will swamp new seedlings, but do not leave it too late in autumn and avoid droughts." The technique could also be used to introduce grasses for early spring grazing, such as Westerwolds or Italians, he added.

Where extra grass was needed in a sward which had become clover-dominant, Francis Dunne of Oliver Seeds preferred to oversow in spring and early summer, as there was less risk of pest problems. But he agreed it would only work for vigorous grasses and was no use for Timothy or Meadow Fescue. He also suggested leaving stock in the field until new seeds started to grow and then shutting it for a silage cut.

Another useful way to increase clover content was to allow existing clovers to set seed and then rely on grazing animals to spread seed in dung.

Swards can be oversown with clover or grasses, but when it comes to keeping out docks frequent cutting or hard grazing can help, says Alan Hopkins.

&#8226 Consider reseeding carefully.

&#8226 Easier to rent grass.

&#8226 Encourage clover.

Leave a sowing gap to avoid clover sickness

ENTHUSIASM for red clover is being dampened by reminders that growing it too frequently in a field will almost certainly speed up the arrival of clover sickness due to either sclerotinia or stem eelworm, or both.

At a Soil Association course, several speakers warned of the dangers. Cotswold Seeds managing director, Ian Wilkinson said clover sickness was not an issue yet, but he urged growers to avoid it by leaving a five to seven year gap between red clover leys.

Asked whether other legumes such as lucerne or sainfoin could safely be grown in that gap, Mr Wilkinson quoted Bob Clements of IGER, North Wyke, suggestion that although the different species had different strains of sclerotinia, they might cr

find a feed cheaper/t of dry matter than a field of grass you do nothing to except cut the hedges every third year, and permanent grassland is less vulnerable to poaching than a new reseed. We keep cows out from March to November and youngstock are out from March to January, so poaching is a concern."

Mr Watson also referred to the way new leys reverted and went through a period of lower productivity than before the reseed. His preferred approach was to rent more land. "It is easier to get 10% more land than to improve grassland productivity by 10% and it is certainly more reliable. Overstocking can be devastating for an organic system. For organic dairying you have to have a big pile of silage."

His only reseeding follows production of organic vegetables, an enterprise run by his brother.

Nevertheless, he warned course members to watch for the downward spiral of productivity which could occur in long term grassland and expressed interest in other ways of improving its productivity.

Alan Hopkins from the Institute of Grassland and Environmental Research, North Wyke, gave delegates some advice on oversowing existing swards with clover or grasses.

"Mow, then graze hard then oversow, ideally using one of the specialist machines. Avoid spring sowing because the existing sward will swamp new seedlings, but do not leave it too late in autumn and avoid droughts." The technique could also be used to introduce grasses for early spring grazing, such as Westerwolds or Italians, he added.

Where extra grass was needed in a sward which had become clover-dominant, Francis Dunne of Oliver Seeds preferred to oversow in spring and early summer, as there was less risk of pest problems. But he agreed it would only work for vigorous grasses and was no use for Timothy or Meadow Fescue. He also suggested leaving stock in the field until new seeds started to grow and then shutting it for a silage cut.

Another useful way to increase clover content was to allow existing clovers to set seed and then rely on grazing animals to spread seed in dung.

Beat docks at establishment

DOCK control starts at ley establishment when seedlings are very susceptible to competition from the seeds mixture and cover crop if used.

"Seed-rate affects the rate of dock seedling emergence and establishment, so the key is a very good seed-bed and a generous seedrate," Alan Hopkins from IGER North Wyke, Devon, told the Soil Association course.

For established docks frequent cutting or tight grazing would keep them under control, he added. And there had been encouraging results in experiments using the Groundhog aerator.

Its tines ripped into dock crowns and the most effective combination was an April treatment followed by another in July. There was evidence that results were better using two passes at right angles.

Mr Hopkins also warned that slurry, especially injected, encouraged docks. "Injected slurry gives a pulse of fertility and soil disturbance, a combination dock seeds can take advantage of." &#42

advice on oversowing existing swards with clover or grasses.

"Mow, then graze hard then oversow, ideally using one of the specialist machines. Avoid spring sowing because the existing sward will swamp new seedlings, but do not leave it too late in autumn and avoid droughts." The technique could also be used to introduce grasses for early spring grazing, such as Westerwolds or Italians, he added.

Where extra grass was needed in a sward which had become clover-dominant, Francis Dunne of Oliver Seeds preferred to oversow in spring and early summer, as there was less risk of pest problems. But he agreed it would only work for vigorous grasses and was no use for Timothy or Meadow Fescue. He also suggested leaving stock in the field until new seeds started to grow and then shutting it for a silage cut.

Another useful way to increase clover content was to allow existing clovers to set seed and then rely on grazing animals to spread seed in dung.