Integrated approach brings black-grass success

Integrated weed management (IWM), with a healthy slice of innovation, has helped Springfield Farm in Worcestershire get a challenging black-grass population over the past decade to levels that can be hand rogued at the end of the season.

The 178-hectare farm, owned by Mzuri drill developer Martin Lole, used to farm very traditionally with a tight wheat, wheat, oilseed rape rotation established
using a plough-based system when he purchased the farm in 2005.

But in 2010 Mr Lole realised the effectiveness and availability of the chemical toolbox was reducing and he began to rethink his whole farming approach.

One of the key changes was moving to a wider rotation, his farm manager Ben Knight says.

“Today we grow oilseed rape followed by a first wheat, an overwintered cover crop into a spring legume before going back into a first wheat again.”

The farm, on Evesham series clay soils, has also moved to a much shallower cultivation system, direct drilling into stubbles using a Mzuri Pro-Til strip-till drill.

That keeps the weed burden in the top few centimetres rather than being mixed through the soil profile and helps make it easier to manage.

STRAW RAKE

Prior to drilling wheat, a 7.5-metre Mzuri straw rake is run at 15-20km/hour across the field up to three times to encourage a chit of black-grass, with subsequent passes also providing some mechanical weed control of emerging weeds.

August rain is helpful to encourage a weed flush, but the Mzuri rake differs from most on the market in that it has a leading disc, which mixes a bit of soil in
as well as disturbance from the following harrows to help with germination, Mr Knight adds.

Using the rake eliminates any need to spray multiple passes of Roundup (glyphosate) pre-drilling, so just one application is used around five days before drilling – following the latest best practice guidance to reduce the risk of resistance developing to the key active.

Wheat drilling begins in October with the fields with fewer grassweed issues prioritised first.

“Challenging autumns haven’t helped with delayed drilling, but because we leave soil structure intact with only shallow cultivations targeted to the seeding zone, it takes rain better and allows water to percolate, allowing us to push drilling dates a little later.”

Drilling with the Mzuri Pro-Til ensures there is good seed-tosoil contact, Mr Knight says.

“A strong wheat population is a great starting point for challenging a weed population and not giving it the space to thrive.

“In the spring because we’re on a slightly wider row spacing – 33cm centre for each of the coulters rather than the more conventional 25cm centres – there is reduced canopy shading effects making it easier to hit the target with spring applications of a mesosulfuron-based product,” he says.

Pre-emergence residual herbicides are the starting point for the in-crop chemical programme.

This season Liberator (flufenacet + diflufenican) + Proclus (aclonifen) was used for the first time and has provided very good weed control, he says.

The addition of Proclus has added another mode of action and is beneficial in avoiding relying on the same chemistry all the time.

The wider rotation is also helping to decrease the risk of resistance developing in black-grass to key actives, such as flufenacet, as well as the use of multiple modes of action.

“We’re getting good efficacy still from Kerb [propyzamide] in oilseed rape and are able to take out a flush of black-grass ahead of spring drilling, which means
we’re not always applying residuals in that autumn slot and giving the black-grass a predictable approach that it can adapt to.

“Everything has a part to play from getting good seedbeds and ensuring we are going to get good efficacy to what we do with our break crops,” he says.

STERILE STRIP

The attention to detail extends to spraying out a 0.5m sterile strip in early April around the edge of each field to prevent ingress of grass weeds from the edge of
the field.

Wheat fields are then hand rogued in late May to early June.

“It’s a zero-tolerance approach.”

After wheat an overwintered cover crop is grown – usually a mix of oats, sunflowers, phacelia, buckwheat as well as volunteer wheat. The main biomass is grazed by sheep, again helping to minimise the use of glyphosate to a single pass.

“It’s important to have a grazier on board who understands that soil is king,” Mr Knight says. “We don’t want the soil poached – I prefer to have a good green tinge after grazing and to keep the sheep moving, but it is just taking down the main bulk to leave a single pass of glyphosate in late February.

“If you grow a big bulky cover crop and don’t graze, you’ll often end up with a shading effect and need two passes of glyphosate and we’re trying to minimise our
use.”

Rolling on a frost is also employed when appropriate.

“If you can catch it on a minus four-type morning it will really knockback the broadleaved species in the cover crop, albeit not completely kill them before a single pass of glyphosate.”

Combining the cultural, machinery and chemical controls has been a very successful strategy, he adds.

“It’s like the Dave Brailsford [Team GB cycling] approach. It’s a percentage game – every little fraction you can do all helps.”

EXPERIMENTING WITH INTER-ROW DRILLING TO REDUCE NITROGEN AND WEED BURDENS

INNOVATION is central to Springfield Farm, whether it is machinery or agronomy related.

One of the latest trials is experimenting with inter-row drilling of small leaf white clover in a standing crop of wheat or barley in the spring before the cereal starts growing away and closing the gap between each row.

Mr Knight says: “With the Mzuri we can lift every other leg out of work to straddle individual rows, offsetting it with RTK guidance to create an inter-row drill.”

The plan is to leave the clover as a living mulch which potentially can help compete with weeds and supply some nitrogen for the following crop.

“The current fertiliser prices are a driver – there’s a lot to be learned from the organic sector and we’re trying to bring the best bits to our farm.”

There was a yield impact in the first year of trialling the system – winter wheat yields were around 70-75% of the usual average, but US trials suggest mowing the clover could release nitrogen and help mitigate the yield impact.

Grazing the clover after harvest could also create an extra income stream, he adds.

“I think if you look at the wider farming system, it has merit, but more experiments are needed.”

SEED RATES

He’s also experimenting with lower seed rates for his wheat in one-hectare plots – down to half his usual 320 seeds/ sq.m for conventional varieties and 100-160 seeds/ sq.m for hybrid wheat varieties.

“The competition the hybrid vigour creates visually seems to give cleaner crops from our observations.”

So far, both yields and weed control have been similar to his usual practice, despite what could be lower competition for the weed from the crop.

“We’re giving space for the wheat to tiller and perhaps band spreading P & K into the seeding zone is giving it a helping hand.

“Over the four years we’ve been doing this there hasn’t been any detrimental effect to weed control.”