Drilling and herbicide advice for Midlands growers in September

Crop Progress

It’s been a miserable summer on the whole, which has led to a frustratingly slow harvest for many. Yields have been better for some than expected, but we’re not going to break any records in any crops. Winter barley was reasonable, oilseed rape okay, and some of the wheat growers I’ve talked to have had some acceptable yields.

That’s probably what we expected – it was reasonably bright but not ever excessively hot, so nothing that suggested yields would be a disaster especially once it stopped raining in May.

I’m going to be interested to see where untreated yields and lower input plots come out in trials because I had a lot of growers saying there was only one and a half leaves left, and how was that going to yield 10t/ha? But I’ve got a feeling it might prove how important flag leaf is and the ones below it less so.

Ben’s agronomy tips for September

1. Is it too late for oilseed rape drilling?

There’s been no shortage of moisture where growers have planted oilseed rape, and some of it came through the ground very quickly. Before the August bank holiday there hadn’t been any reports of cabbage stem flea beetles but we know how quickly that can change.

While conditions have been good for drilling in August, with the delayed harvest, there might be some fields destined for oilseed rape still to be drilled. Unless it is incredibly dry there is still a window in September for establishing oilseed rape, at least in the first 10 days of the month. I’d be a little nervy going too much after that unless you have an exceptional variety that can get to a sensible size in the event of a hard winter.

Even for early September plantings, you’re ideally looking for a variety that gets up and away fairly quickly as you want get it through the growth stages susceptible to flea beetle and slug damage as quickly as possible.

Most varieties claim good autumn vigour, but there are degrees of ‘goodness’. Most breeders have one or two that do race through growth stages quickly, particularly hybrid varieties, so I’d recommend something like that.

2. What about cover crops?

A lot of cover crops mixes include brassicas, as well as other species, so if it is still okay to plant oilseed rape, it is probably fine for cover crops, depending on conditions.

Again there might be later cut winter wheat fields that are planned to go into over winter cover crops or even 12 month options in an environmental scheme, and there’s no reason why they can’t still be successful in September, although you might not get the same biomass as from an August planted crop.

Certain species will also likely do better than others, so choose your mix carefully, or be prepared that some species in a multi-species mix might not establish very successfully, especially if planting later in the month.

3. Steel will help steward glyphosate

Deciding how much cultivation to do, and when, post-harvest is always a tricky balance. From a glyphosate stewardship point of view, there should be a degree of cultivation involved in pre-drilling stubble cleaning because it is a proven fact that steel is an important part of the active’s stewardship.

Doing a cultivation pass between two applications of glyphosate, particularly if you’ve got some bigger grassweeds present is definitely good practice. The difficult is when it then goes dry for four weeks and you’ve removed any moisture that was within the seedbed. It’s easy to see why growers are sometimes reticent, and not just for their carbon credentials to cultivate in that situation, but I prefer not to be completely reliant on chemistry.

With the amount of moisture around currently and judging by the volunteer mat in some fields that have been cut, there’s probably less need to cultivate this year to encourage a chit. It probably makes more sense to spray that off before cultivating, although it is possible, of course, to do it the other way round.

Getting rid of a large proportion of volunteers relatively early will also help reduce barley yellow dwarf virus risk. Clearly from the BYDV issues we’ve had this year in some cases spraying off volunteers very close to drilling might have been a significant factor in the problems by not providing a long enough gap to prevent carry over of virus into the new crop.

We commissioned some trials work last autumn, which showed that spraying off volunteers 10 days prior to drilling was optimum for reduction in BYDV, while some NIAB research suggested that a slightly wider gap between a first application and a second one, maybe 48 hours before drilling, was the best way to go for weed control.

Going 10 days before drilling does leave some risk of grassweed emergence in the intervening period, particularly if it is moist. So while it probably means the best for green bridge is two applications within two weeks before drilling, it might be the best plan is to spray off a large population of volunteers a bit further in advance, ideally cultivate, and then apply a second dose of glyphosate quite close to drilling, or even with the pre-emergence, although that does limit some pre-emergence mixes because three herbicides and glyphosate is probably pushing things a bit.

4. What cereals can you drill in September?

In my part of the world, drilling in September is probably a bit of winter barley and wheat if you’re lucky enough to be one of the few with fields that are not under a major threat from grassweeds there is the potential from some drilling towards the end of the month.

Even with that I’m a little nervous because not only because of the grassweeds, but last season has proven that the best fungicide on the market is drilling date, and the second best is variety choice.

So you are potentially putting yourself at greater risk of things going wrong in the spring by drilling wheat in September, if we have another season as bad or worse for disease pressure. There’s a short list of varieties that have good enough disease resistance to be drilled in September, while ones that growers might like to put in, for example Dawsum, quickly have Septoria ratings that don’t look great if it is drilled in the third week of September.

And if you have serious black-grass or Italian ryegrass then it’s madness anyway to consider planting in September.

5. What herbicide options are available if you plant barley?

Our main option is Liberator (flufenacet + diflufenican) + Proclus (aclonifen) at the lower rate of 1.0 L/ha of Proclus. However, if you are on light land or if getting seed in the ground to the required drilling depth of 33mm is a problem then other options might be safer.

Traditionally we would say you need to be more careful about crop damage in winter barley than in wheat, and with competition being one of barleys greatest attributes when it comes to grassweed control, taking out 10-15% of plants with a too strong pre-emergence herbicide mix is clearly not a clever thing to do.

I would probably steer more to some of the traditional mixes, such as Liberator + pendimethalin, but if you are planning to use Liberator + Proclus make sure you avoid having too many overlaps.