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Spring barley offers “near-perfect” black-grass control The value of spring barley in helping to reduce high black-grass populations has been clearly demonstrated in a farm trial being carried out on heavy land in Leicestershire. Background populations of blackgrass at the site near Harby approach 500 heads/m2 in the worst-affected fields, and farm partner and BASF marketing campaign manager Ruth Stanley (right) says that, despite the amount of pressure, the plots of spring barley are almost clear of the weed. The trial followed spring beans and received two glyphosate applications pre-drilling. KWS Irina was sown on 1st April in 36m-wide plots using a direct drill to minimise soil disturbance to reduce further black-grass germination. Four different seed rates were used, from 250–550kg/ha to see what effect this might have on black-grass suppression. Crystal (flufenacet + pendimethalin) was applied at 2-litres/ha. Despite difficult conditions – the soil was wet and the drilling slot remained slightly open after drilling – the crop established rapidly, overcoming potential slug pressure. Ruth says: “There’s hardly a blackgrass plant to count. The glyphosate cleared autumn-germinated plants, and the Crystal has done a great job.” With little or no black-grass left to control, and given the good ground cover achieved even at 250kg/ha, seed rate made no difference, she adds. The work reflects current practice at the farm, where a third of the 400 hectares (1,000 acres) has been springcropped.

Barley introduction Barley was introduced to lengthen the rotation, with the fields worst-affected by black-grass being put into spring barley. Ruth explains: “We had been operating a wheat-based rotation on heavy land with no ploughing and a reliance on chemical control. Over the past three years we’d seen a marked increase in black-grass to the point where it was having an impact on yield. “We realised we had to change what we were doing. “We know from our previous trials at Harby and from wide experience elsewhere that spring cropping and managing whereabouts black-grass is in the soil profile are key to black-grass control.

“We also know that barley is more competitive than wheat, hence the change of tack for this year’s trial.” The ability of winter barley to suppress black-grass is also being assessed at Harby. Unlike the spring plots, seed rate made a difference, although none of the plots achieved good enough suppression to adopt commercially until black-grass pressure has been reduced, adds Ruth. Two-row feed varieties KWS Tower and KWS Glacier plus six-row hybrid Volume were direct-drilled on 5th October following a pre-drill glyphosate application. All plots received 4-litres/ha of Crystal and 0.2 litres/ha of DFF pre emergence. Follow-up peri-emergence treatments consisted of 0.45-litres/ ha of Axial (pinoxaden) + Adigor adjuvant + 1.75-litres/ha of Stomp Aqua (pendimethalin), or 0.5-litres/ha of BAS 758 H (flufenacet + picolinafen) + 1.75-litres/ha of Stomp Aqua. By late May KWS Tower appeared to out-compete more black-grass due to its sheer height. Although plants were still there, they were smaller than those in the Volume plots and likely to return fewer viable seeds, says Ruth. An untreated plot of KWS Tower sown at the highest seed rate (390 seeds/m2) contained 142 plants/m2 on 31st March. The Axial-treated area contained 73, and the area sprayed with BAS 758 H contained 62 plants/ m2. KWS Glacier at 310 seeds/m2 contained 292, 214 and 154 blackgrass plants/m2 for the respective treatments. Ruth says: “This trial clearly illustrates the potential of barley variety and chemistry combinations to suppress black-grass. “However, on this farm at least, spring barley definitely looks the more promising approach. “Until we can reduce the background population to a more manageable level, there’s too much black-grass pressure for winter barley, and we only have a limited chemical armoury with which to control it.”

Soil trial A further soil trial was included this year at Harby to see whether anything can be done in the autumn to help suppress black-grass numbers while improving spring barley establishment

Visitors at BASF’s Harby open day.

on heavy land. To deliver competitive crop growth, the soil’s physical, chemical and biological components need to deliver significant agronomic benefit. In particular black-grass likes cold, wet soils, therefore improving aeration and porosity can help disadvantage its germination and establishment, says remote sensing agronomist Neil Fuller (right) of 2Excel BioSystems. Three treatments were carried out. Part of the area received digestate on 18th September, another was dressed with gypsum at 1.5t/ha on 24th September and a third was mole ploughed to 45cm on 3rd October. “The benefits of good mole ploughing are well known,” says Neil. “Steel and diesel give a nearimmediate improvement, provided conditions are right.” Digestate helps boost a soil’s biological properties by building humus, which binds soil particles like a flexible polymer. This means it can take more of a load without collapsing and will drain better, says Neil. “This will take time, probably two to three years on this site, before the real benefits start to show. “Gypsum is attempting to do the same job chemically, introducing calcium to reduce the binding power between clay particles. Over time a crumb structure is produced from the surface downwards. “All three treatments could be used in various combinations and with other options such as cover crops to help open soils. All these things work. It’s a question of picking the right approach for the farm,” he adds. Apart from a pre-drilling glyphosate, no chemistry was applied, to make any differences between the three treatments more obvious.

The digestate-treated area contained an average of 170 blackgrass plants/m2, the gypsum-treated about 112, and similar where the ground has been mole ploughed. Ruth believes that the digestate might have improved fertility enough to aid black-grass establishment and survival in the spring.

Commercial oats Part of the plots were sown with commercial oats using a power harrow combination drill in November, to act as a cover crop to draw moisture out of the ground over the winter to improve drilling conditions. They were sprayed off with glyphosate pre-drilling. The black-grass count dropped to about 70 plants/m2. Ruth suggests this might be due to better crop competition and an increased black-grass chit when the oats were drilled, reducing the seed bank. This flush would have been caught by the pre-emergence glyphosate. KWS variety specialist, Rose Riby agrees that, being competitive and fast-developing, spring barley looks to be the crop of choice to help suppress black-grass. She says: “Although KWS Irina is a brewing variety, it can also be pushed for yield and is the perfect answer on land where barley isn’t traditionally grown for malting, with the highest scores for resistance to lodging and brackling on the Recommended List.” If growers choose to raise seed rates to suppress black-grass they will need to consider their market carefully, she adds. The crossover point between yield optimisation and when screenings start to rise is between 250–300 seeds/m2. If it’s necessary to use higher rates than this, then a feed home is likely to be the better option, she advises. ■

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Farmers Guide Magazine August 2016 Issue