Article taken from Arable Farming Magazine
As flag leaf fungicide spraying draws to an end, it is a good time to review the success of grass-weed control programmes and start to put action plans in place which may have a major effect on next sea-son's cropping plans. On fields where we are losing the battle with grass-weeds, despite large herbicide spends, radical approaches to whole farm policy may be required if we are going to continue to successfully grow cereal crops in these fields. In order to take pressure off our depleted chemistry set, it is going to be important we utilise cultural control as much as possible. Cultivations could have a huge role to play. If control has been particularly bad, ploughing could be considered in order to bury black-grass seed. Undisturbed deep-buried black-grass seeds are likely to lose viability at any-thing up to 70% per year. But for this technique to be successful, it is important any surviving seeds are not brought to the surface the following year, so only rotational ploughing will be useful. If on the other hand black-grass control this season has been good, then minimum soil disturbance could be the best practice.
Other popular cultural options include using high seed rates of aggressive varieties to help out-compete black-grass, and while this may help, it is certainly not the complete answer. Achieving a good, consolidated seedbed in order to give residual chemistry the best conditions to work in is a must, and if there is plenty of moisture, stacking residual grass-weed herbicides with different modes of action can still provide good levels of control. This can be further improved by applying triallate (Avadex) to the programme and for this autumn the approval in wheat of ethofumesate will certainly bolster residual activity. Delaying drilling to allow multiple stale seedbeds and the peak autumn flush of black-grass to be completed before sowing takes place can also be useful in reducing black-grass populations, however it does bring its own risks, as last autumn demonstrated.
Consistent
Spring cropping is undoubtedly one of the most consistent ways of reducing black-grass populations. There are potential issues with this, however. The worst black-grass fields tend to be the heavier, colder soils which are not ideally suited to spring cropping, and sec-ond, if we turn to more spring cropping, will the population dynamics change within the black-grass population and encourage more black-grass to germinate in spring? The use of cover crops prior to spring crop-ping can alleviate these two potential problems. The correct choice of autumn-sown cover crop, based around black oats and legumes, will help structure the soil, allowing the spring crop to be direct drilled with minimal soil disturbance and not encouraging the black-grass to be 'woken up' in spring. Furthermore, the roots from the destructed cover crop work hand-in-hand with the direct drill stabilising the soil and minimising the risk of disturbing black-grass seeds in spring.
Agronomist facts
►►Chris Martin is a technical manager for Agrovista, based in the north east of England. His role is to provide technical advice to growers over an area extending from Lincolnshire to Scotland. Prior to this, he was an agronomist with the company for 15 years and continues to provide agronomy advice to a number of growers producing combinable crops in the Scotch Corner area