Dealing with dry conditions for cereal establishment

Dry weather has meant harvest is progressing rapidly, with many farms already finished. Looking ahead to autumn, continued dry conditions could cause some difficulties and opportunities for drilling crops this autumn.

1. Patience essential for stale seedbeds

“In such dry conditions, there will be little germination of weeds and volunteers whether you cultivate or not,” says Bayer’s Roger Bradbury. “Usually when it is this dry, the best option is to do nothing from a weed control perspective.”

Weed seed viability is affected by prolonged exposure to sun and heat plus there is predation from small mammals and birds, all helping to reduce weed numbers without any active intervention. However, Mr Bradbury acknowledges there are other reasons why farmers may need to cultivate.

“This season, the challenge is having enough moisture to get a good flush before using Roundup and then drilling. Likewise, moisture will be essential for crop establishment and pre-em herbicide performance, so patience is going to be key.”

Mr Bradbury urges farmers to wait until there is a proper flush of weeds before going in with Roundup. Spraying off sporadic germination before soils have properly moistened up is not helpful for the long-term stewardship of glyphosate or a good use of farmers’ time or money.

2. Don’t assume all is well with soils

A dry harvest generally means less soil compaction at harvest and less cultivation needed to put things right. But very dry conditions can pose problems on certain soil types.

Farmer David Felce thinks it may be a challenge to get things ready for drilling. “On my farm, the soils have dried into large plates. The cracks are so big that you can fit your arm in. I’m not sure that we will get enough rain, or the right kind of rain, to reconstitute the soil properly before harvest. Any thunderstorm will wash fines into the cracks, which won’t help.”

“For the time being, many people are happy to wait and see if we get rain. That’s ok for now, but at some point, maybe from mid August, we may have to start preparing seedbeds.” He recognises that a lot depends on soil type and location, but many farmers will be in a similar situation.

3. Moisture important for pre-em success

Barley drilling is little over a month away, and wheat soon after. Protecting the crop with a pre-em herbicide application is a cornerstone of effective grass weed management alongside cultural controls.

Good soil moisture levels are ideal for drilling and spraying but this autumn, there may have to be some compromise in order to complete drilling to schedule. In such instances, farmers should look at which herbicides can still perform in this situation.

Dry weather performance is a useful feature of aclonifen, but farmers are urged to think of it as useful back up rather than a licence to drill and apply herbicides in very dry seedbeds. “The best results still come from a mix of Liberator + Proclus at the true pre-em timing, to a seedbed with sufficient moisture” says Tom Chilcott of Bayer. “Waiting for seedbeds to moisten up is a better option, but it may not always be possible, so using a mix with aclonifen gives you a bit more flexibility in a dry season.”

Research in sunflowers1 has shown that aclonifen is not significantly affected by soil moisture, so is suitable for use in drier conditions. It also has a longhalf-life of approximately two months so will provide protection long into autumn even when used at earlier timings, for example in winter barley.