The future management of blackgrass weeds in cereal crops is of more than significant interest to Irish cereal growers.
Hence, the relevance of the blackgrass trials, which are now taking place at Stow Longa in Cambridgeshire.
The projects have been developed and managed by agronomists with the Agrii organisation.
The work has one, overriding objective: To develop rotation and cultivation-based techniques as a means of controlling herbicide-resistant grass weeds.
This list includes blackgrass, bromes, and ryegrasses.
The trial work to date has identified a number of factors that will impact on blackgrass plant numbers. These include: Planting date, the rotations followed, and min-till versus ploughing.
But driving all of this is a fundamental knowledge of the soil that is actually being worked. At the Stow Longa site the non-organic fraction of the soils have a 51% silt content.
This is an extremely mobile component within any profile and plays a key role in developing soil pans if zero or min-till cultivation options are practised on a consistent basis.
The work at Stow Longa has been supported by Lemken from the get-go with the results generated from the work used by the company to develop its own views on the future of tillage machinery design.
Lemken has also been to the fore in communicating the results of the trials to Irish tillage farmers.
Blackgrass
Blackgrass is now endemic in many parts of England. Plant numbers in excess of 200/ha can reduce overall cereal yields by up two 2t/ha.
The Stow Longa work has consistently confirmed the impact of planting date on blackgrass control.
Where winter cereals are concerned, delaying drilling dates into October provides growers with the opportunity to maximise the control of autumn germinating blackgrass plants.
The inclusion of spring cereals within a cropping rotation is another factor that helps to drive down blackgrass populations.
The Stow Longa trials have included the use of spring oats and spring barley in this context. Significantly, oats have proven to be the better option under the soil conditions and climatic that prevail in the east of England.
Driving all of this is the fact that growers going in with a spring crop have the opportunity to control blackgrass plants that have germinated over a six month period.
Significantly, hybrid barleys also perform well under high blackgrass pressure.
The work at Strow Longa has consistently confirmed that this winter cereal option can out-compete the weed under most growing conditions.
It is worth noting that the 2023 hybrid barley plots stand out above all the other crop options, in terms of their yield potential.
But the big question, from a cultivation point of view, comes down to the following choice: The plough or some form of min-till option.
The results achieved to date indicate that continuous min or zero-till does very little to aid the control of blackgrass.
However, coming in with the plough after five years acts as a re-set button.
Plough
The highest yields and greatest margins generated at Stow Longa have been consistently achieved from crops that were established using a plough-based system, following a period of min-till.
Ploughing on an annual basis may not be the preferred option ion many farms from an economic- and possibly – an environmental perspective.
However, the use of the plough buries blackgrass seeds to a depth that prohibits their subsequent germination.
Disturbing the surface of the soil is not recommended as this will only bring up blackgrass seeds that are located at shallow depths
The crop margins generated by the Agrii trials also confirm the tremendous impact that heavy infestations of blackgrass can have on final crop financials. In 2022, the range in overall gross margins came in at £1,821/ha.
Last year saw winter beans, established using a min-till system, generate the poorest gross margins of all the crops included in the current blackgrass trials.
The Stow Longa site is sub divided into six, 1ha blocks.
In addition, all the trials have confirmed the absolute necessity of producing a firm seed bed, one that maximised the amount of contact between the applied seed and the soil.
In practical terms, the top 2in or so of soil must have a fine texture.
This allows seeds to make strong contact with the soil, thereby generating high levels of nutrient exchange and new root development.
Only in this way is the crop guaranteed to get off to the best possible start.
One of the most recent trends identified by the Agrii team at Stow Longa has been the increase in brome numbers within crops grown on what has traditionally been a blackgrass farm.
It is expected that a similar trend will be replicated on other tillage farms
Brome is another herbicide resistant weed. However, the plant’s cycle can be quite effectively broken by including a spring crop within a cereal rotation.