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suggests that only 3 per cent of seed survives 3 years of burial Seed shedding patterns: from mid-June in winter wheat and a little later in winter barley, but most is shed just prior to harvest
Shallow stubble cultivations Dr Moss said that Danish research work has demonstrated that while it is popular for growers to cultivate stubble immediately after the combine to stimulate grass weed germination, it may be better to delay that action. “As long as there is some moisture, black-grass seed will germinate on uncultivated stubble and so it’s questionable as to how much shallow cultivation will help,” he commented. “It may simply increase the likelihood of encouraging older black-grass seeds to germinate from previous years but help preserve freshly shed seeds,” he added. “We don’t really know enough about the relative benefits of shallow cultivations under different weather conditions and it’s what comes up in the following crop that’s important, not so much what comes up beforehand,” he continued. “Possibly the best cultivations
are those that give you the best seedbed for drilling a wheat crop in mid-October and which also provide the best conditions to maximise the efficacy of pre-emergence herbicides which tend to work better in October than September. I understand that there are conflicts in terms of field operations at that time of the season, and we don’t have all the answers, but drilling at that time could be the driving force for getting on top of black-grass.” He also referred to AHDB Cereals & Oilseeds-funded trials work carried out by NIAB TAG (2010–2014) that resulted in 33 per cent less black-grass plants/m2 being found where autumn drilling was delayed by three weeks from mid-September. Results also showed 50 per cent less black-grass heads/m2 and 25 per cent additional control from pre-emergence sprays used. “Each black-grass plant is 55 per cent less competitive in late October compared with late September drilled crops,” he added.
Autumn to spring Turning to the benefit of spring sown crops in the battle against black-grass he highlighted that Rothamsted trials had shown a
Summer Deal
mean reduction of 88 per cent in the amount of black-grass when changing from autumn to spring drilling, across five different years between 2001–2012. “Again, spring cropping is not a complete solution and if most of your black-grass germinates in the spring, then it’s clearly not the answer. But growing two or three spring crops in succession can be very effective. “Fallowing or grass leys is also a consideration for growers but one year of either of these is not enough. Two to three years is better but grass must be well managed to prevent seed return. Alternatively, a flexible approach to spraying off black-grass patches in early June within crops for several years if necessary – a sort of ‘patch fallow’ – can prove very effective.” For growers in non-traditional black-grass areas, such as northern England, Wales, Scotland and Ireland, where signs of resistance may appear due to contamination via seed lots or straw, they should target patches with a sprayer or knapsack (if only small patches), or hand rogue, where
possible each summer, he advised.
The sky’s the limit Drone operating company Ursula Agriculture was represented at the event by Alex Dinsdale, and he suggested that the company’s UAV fixed wing aircraft (compared with rotary or manned alternatives) was the most suitable for monitoring and recording black-grass occurrence on UK farms. According to Mr Dinsdale (left) the Ursula fixed wing drone can cover approximately 40ha (100 acres) in 30–45 minutes of flying, before producing a digital map for farmers to then use for identifying and then spraying off black-grass infestations and patches. Operations are usually carried out in May and June when black-grass is appearing above wheat crops. Mr Dinsdale said the system could also offer crop performance monitoring – highlighting the best or worst performing crops in individual fields – with a view to better nutrition planning. Suited to enterprises of 200ha (500 acres) and larger, costs can vary between £10–£20/ha. ■
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10 www.farmersguide.co.uk September 2015
1-27 ROP Sept.indd 10
15/08/2015 15:00