Be careful when sowing spring crops into land coming out of long-term set-aside or pasture, warn independent agronomists.

Pests, diseases and weeds could be more troublesome than some growers imagine, believes Wiltshire-based John Clark of Agronomy One, whose comments are based on discussions with other Association of Independent Crop Consultants from southern counties.

Land coming back into production after years in set-aside will have accumulated a whole range of threats to new sowings, some of which growers may have forgotten about, says Mr Clark.

Much set-aside has already been sown to winter wheat, he acknowledges.

“Some areas have been left because glyphosate effects were poor, leaving too much rubbish. Other fields didn’t plough well or growers may have left their sowing decisions too late or while other had planned to sow a spring crop.”

He foresees two main potential problems – pests and take-all – the main line of defence against pests being cultural.

“Ideally, you needed to have got glyphosate on in the autumn and the land ploughed up as soon as the weather allowed.”

The longer it is left in furrows the more the pests and their eggs will be exposed to wet, frosty conditions, birds and drying winds, which reduce their numbers, he says.

“We’re talking about ley pests, and there’s a range of grass/cereal flies and grass moths which attack the new crops.”

Wireworms are another threat, especially in maize and spring barley, as there is no chemical spray for control. Traditionally a problem of heavy land, wireworm has made a come-back, even on light chalk soils.

“Maize seed should be dressed with Gaucho or Cruiser, and spring barley dressed with tefluthrin-based Evict or Austral Plus against wireworm.

“As members of Crop Advisors buying group we have already secured these dressings and most spring barley seed is on farm.”

Slugs could be an issue.“It’s worth looking out for the black arion species that feed underground and tend to go for crops rather than pellets. Their damage can easily be confused with that of leatherjackets.”

Peak feeding time for leatherjackets is February to April, and high numbers may justify spraying with Dursban (chlorpyriphos).

“It may be worth adding a silicone wetter to help move the chemical into the soil, but remember that chlorpyriphos won’t kill wireworms.”

Loose soils favour all these pests, so rolling after sowing is important to restrict pest movement.

“You need to get the soil down tight to restrict their movement.”

Frit fly is more of a problem in spring oats than barley, where again chlorpyriphos treatment might be required.

“Spring cereal growers can help themselves by sowing as early as January, but good seed-bed conditions are paramount allowing the plants to develop a good root structure and establish three leaves before the pests wake up.”

Glyphosate should have dealt with most weeds, although heavy infestations may need two applications, he notes. A large seed bank of both perennial and annual species will have built up, so growers must be prepared to tackle them in the crop.

“In severe cases it may be worth leaving cropping for another year and drilling in autumn 2008.”

Couch carries take-all, the other key threat from set-aside.

Maize offers the further chance to reduce couch by using Samson (nicosulfuron) in the growing crop, he suggests.

Bringing set-aside from part fields back into production has rotational implications, says Mr Clark.

“The difficulty will be trying to fit the new area into carefully balanced rotations while maintaining some kind of block cropping for efficiency.

“Bear in mind that if you sow winter wheat or winter barley in 2008, a Latitude (silthiofam) or Jockey (fluquinconazole + prochloraz) seed dressing will help against take-all, and is especially important where couch has been an issue.”

Spring barley growers should remember that pre-harvest glyphosate for any remaining couch can affect malting germination.

“Also soil residual nitrogen may have built up in the fibrous root systems under set-aside and will need taking into account where malting premiums are important.”

Spring barley is post set-aside choice on chalk

Peter Crossman (above right with John Clark) of Manor Farm, Upton Lovell in Wiltshire, has taken out about 20ha (50 acres) of long-term set-aside on thin chalk.

“The decision to grow spring barley was based on the farm’s ability to produce a malting sample every year, and our belief that the malting barley price is more stable than the wheat price.”

The spring cropping decision allowed plenty of time for glyphosate to be effective and the barley straw suits the dairy enterprise, he says.

“The stubble is beneficial to partridges and our shoot,” he adds.

Agronomy tips for spring cropping after set-aside

• Beware of pests and take-all
• Plough as soon as possible to help reduce pest threat
• Be sure to treat maize and barley against wireworm
• Arion slugs feeding below ground could be troublesome
• Heavy leatherjacket infestation may justify treatment
• Roll to restrict pest movement
• Watch out for frit fly in spring oats
• Sow barley early, provided conditions permit, to create strong plants
• Large seed banks likely, so be prepared to treat weeds in crop
• If severe weed infestation expected consider sowing delay until autumn
• Scope to reduce take-all-bearing couch in maize with Samson herbicide
• Consider rotational impact
• Autumn cereal seed should have take-all treatment
• Be sure to take residual soil N into account