Black-grass control begins with understanding first principles and then tailoring a plan depending on the level of infestation. CPM finds out more.
Few problems generate as much discussion as black-grass and farmers are always looking out for new methods to control it. However, with so many different ideas out there, how do farmers work out what’s required on their farm?
For Dick Neale, technical manager at Hutchinsons, the most important thing is always to refer back to some basic principles of black-grass control when deciding what to do.
“I think confusion has come from cherry-picking little pieces of advice from different experts and other farmers,” he says. “People tend to choose ideas they like the sound of or ones that they can easily do on their farm, without necessarily thinking about how it all knits together into a single system.”
The foundation for any control programme is understanding the black-grass population on the farm, he believes. Dick highlights the importance of understanding the probable effects of previous management decisions, but also knowing where black-grass seed is distributed across the farm, as well as within the soil profile.
After taking these points into account, he would then assess the level of seed return this season before making any final decisions for season 2019-20.
“There’s no substitute for getting out in the field and then being critical about what’s happening on your farm before deciding which fields need what treatment,” he says. “Go out and do some headcounts because it’s all too easy to underestimate black-grass populations. Even counts as high as 400/m2 can appear ‘not that bad’ when looking out across the field.”
Essentially a good understanding of the black-grass population is the start of planning how to manage it, he sums up. Bayer’s Dr Gordon Anderson-Taylor shares Dick’s view that managing populations is the key to black-grass control.
“We’ve always encouraged using herbicides as just one of the tools to manage populations. It may sound obvious, but the aim is to reduce seed return from one season to the next so that the overall population size reduces.”
The initial size of the black-grass population will determine what measures are needed. “Smaller populations may only need delayed autumn sowing and a good residual stack to sufficiently limit seed return, but when there are several hundred heads/m2 more radical action is required,” says Gordon.
On high pressure sites, it’s now well established that spring cropping with barley or another competitive crop is the best option to seize the initiative against black-grass. On land that’s clean enough for winter cropping, it’s still a necessity to manage the situation carefully to establish a clean crop.
“Black-grass has two main flushes, generally in the third week of Sept and the second week of Oct, so the aim is to drill after the black-grass has germinated and been sprayed off –– typically from 15 Oct onwards,” says Dick.
The gap between harvest and drilling is also an important time for black-grass management. “There’s historically a tendency to cultivate straight after the combine –– a hangover from the days of deep (10-20cm) non-inversion tillage. Nowadays, for black-grass control the cultivation is much shallower, ideally in the top 5cm, so that this season’s seed return isn’t mixed deep into the soil profile.
“Shallow cultivations needn’t be done in August. In fact, post-harvest soil is often in good condition to drill, meaning there’s no need to work it unnecessarily. Working soil can often be done to best effect later, in mid-Sept, and this will stimulate black-grass germination but helps ensure the seedbed remains in good condition until a later drilling date. Cultivating in August can leave the seedbed exposed and cause it to wet up too much.”