Moisture, drilling and weed control advice for September in the Midlands

Crop Progress

Harvest finished for most before anything fell from the sky, even the spring beans which have disappointingly marked the end of combining.

In contrast, winter wheat yields were staggeringly good considering the conditions they’ve been under for the past few months. How they have achieved it I’m not entirely sure, but it must be a combination of rooting we never believed happened, happened, and sunshine hours through the roof. It probably wasn’t too hot, too early. If the really hot weather had come earlier in July it might well have been different.

Combined with most growers having achieved or the potential of reasonably attractive average grain prices, most farmers seem pretty happy.

Winter barley and oilseed rape yields have also been reasonable to decent, spring barley mostly okay, while spring wheat less clever.

Ben’s agronomy tips for September

1. Choose varieties with high vigour for September drilling

Believe it or not you need moisture to establish oilseed rape, and in some parts of the Midlands that has been lacking. Of course, some parts have had considerable amounts of rain, while others have had no more than 2mm.

Even where some fell quickly in one go – for example close to me 11mm in 45 mins – it’s not really that helpful. A lot of growers were still holding off drilling oilseed rape as we led up to August bank holiday.

But many will still be keen to give it a go with early to mid-September drillings because of the good price. Variety choice will be important – picking something that will fly out of the ground and get it beyond the peak of cabbage stem flea beetle adult grazing, and get to a reasonable size before winter.

That probably favours hybrids, such as our DK Exstar, which has good autumn vigour. But there are other options from other breeders so growers shouldn’t be too limited in availability of varieties that would suit.

As we get later in September, varieties like DK Exsteel and the Clearfield variety DK Imove, are decent options.

Obviously, moisture, moisture, moisture is the real answer to getting crops away quickly, but tactics like using smelly organic manures to make crops less attractive to cabbage stem flea beetles, growing trap crops and planting into long stubbles never seem to be detrimental, even if the evidence of a positive effect is variable.

Ultimately if you have missed all the decent rain going into September the key is to be ready to drill, but don’t force it as there will be opportunities. It is possible to get good oilseed rape yields even from later September drillings, albeit with a bit luck with the autumn weather.

2. Be careful with glyphosate rates

While there probably isn’t much moisture currently for many to lose if they do cultivate stubbles, the question is why / what are you trying to achieve?

Generally there’s probably not many scenarios where you need to cultivate, especially a deep cultivation at this point, in case you are pulling up any moisture to lose, and also stimulating weeds to germinate that might not otherwise. 

At the beginning of September you’re still, hopefully, at least six weeks away from drilling wheat in the worst grassweed scenario. At some point in that period there will be some rain, and with low dormancy of black-grass, there’s likely to be a flush of germination regardless of any cultivation. I’d be tempted to see what comes without cultivating, especially if you’re using a low disturbance system.

The situation is different for weeds, such as sterile and great brome that do like to be cultivated and covered with soil to get some darkness before they germinate. Here a cultivation might be more useful.

When it comes to spraying off a flush, and I know you will read this and say he would say this but be careful with glyphosate. It’s no longer a cheap resource, but because of that, please don’t scrimp on rates. The absolute minimum should be 540g a.i./ha for 2-3 leaf grassweeds, and the moment you start to see a tiller it should be 720g a.i./ha.

There is no resistance, but weeds do become tougher to control over time as we see from projects like BGRI (Black-grass Resistance Initiative) and recent NIAB resistance testing. Those show there is a range of sensitivity within any population to any actives, and for some 540g a.i./ha is only just above the borderline. In the BGRI project when they used lower doses there was a marked drop off in control levels.

While you might be putting 540g a.i./ha in the tank and thinking that’s what you’re applying, if you do not do a good job with the application or the conditions are marginal you might not be getting 540g/ha near the target. Any degree of lock up because of calcium, magnesium or iron in the water can also be a problem, and might need higher doses or a water conditioner to help.

Application is key – too many travel too fast, with too big droplets with the boom far too high, thinking it’s glyphosate and will work anyway. That might be the case 10 years ago, but it isn’t the case now. In reality application technique should be similar to what you would use with a post-emergence contact like Atlantis (mesosulfuron + iodosulfuron).

3. Consider a new option for winter barley weed control

No doubt there will be some winter barley drilled in late September, and we have a new option available for grassweed control with an extension to the label of Proclus (aclonifen) into winter barley.

I’m less enthused about it than I am in wheat, where used in conjunction with Liberator (flufenacet + diflufenican) it really is a standout above the options we have had previously. For winter barley the maximum dose is 1.0 L/ha compared with 1.4 L/ha for crop safety reasons and the difference in rate does take away some of the benefits we’ve seen in wheat.

Winter barley is more sensitive so be careful – seed depth is important, as are seedbed conditions, avoid overlaps when spraying and use sequences rather than the bigger tank mixes you might have used in winter wheat.

But it is a new mode of action for the crop and is in the mix of options you might consider. My view is it will especially suit growers with good seed depth control when drilling, have auto shutoff on the sprayer, probably growing barley on heavy land in poorer situations for grassweeds.

4. Delay winter wheat drilling into October

I’d never say don’t drill wheat in September but try not to drill wheat in September on fields with significant grassweed pressure.

There will likely be some concern that once it starts raining, it won’t stop, like a couple of years ago though which might create some pressure to drill. Just be careful which fields you pick, and obviously target those with historically lower grassweed pressure or where you have achieved excellent grassweed control for a couple of seasons in a row and you’re not going to be turning over soil to bring up weed seed.

Even in those cases earlier drilling for me would still only be from around 9 October rather than September.

Things to remember if you do drill in September is that with warmer soils there will be less residuality from herbicides.

That potentially means more actives in the stack or longer lasting actives, or more likely there will be a benefit in using a split programme to get the longest length of activity.

You also need to expect a flush of grassweeds in the crop a few weeks later in October and depending on what you use as a pre-emergence it might be gone by then. The longest lasting actives are pendimethalin, diflufenican and aclonifen, so they are worth considering.