Integrated approach to stop ryegrass spread
Many arable farms now report ryegrass poses as greater a challenge as black-grass, if not worse. It is especially competitive with cereal crops and has a greater ability to spread.
Furthermore, Dorset farm manager, Rob Burden, is having to cope with resistance issues that limits options on the 520 hectares of arable cropping at Chilbridge Farms.
Although historically a mixed-farm including rotational grass leys - with the Richards family’s previous livestock enterprises including a dairy, pig unit and chickens - ryegrass, and particularly issues with resistance, can be traced back to an acquisition of additional land in the mid-2000s.
Since then, it had progressively spread at low levels across a significant area of the farm, before the full implication of the resistance became apparent. Now, some fields are affected to a situation where agronomy decisions are primarily driven by the need to minimise the competitive yield losses and stop the further spread.
“We are currently only containing the extent of the ryegrass problem, but we do feel that we are certainly getting better at containing it with the tools being used,” he said.
Resistance testing, repeated over different seasons, confirmed resistance which had limited his herbicide options and instigated a fully Integrated Crop Management plan to tackle the weed issues.
Rob highlights he is now meticulous about cleaning machinery moving between fields at harvest – including contractors coming in to bale or move straw. It has been clearly apparent that the historical first ingress of the weed into previously clean fields can be pinpointed to headland points where the combine had been cleaned off and serviced, he reported.
Post-harvest, the routine is to get in with a straw rake as quickly as possible, to scratch a top tilth that will encourage any grass weed seed to chit, but without burying it too deep for germination. Where time allows, a second pass with the straw rake can tickle up a second flush. Rolls are invaluable to conserve moisture and encourage emergence, he added.
For autumn establishment, Rob aims for a one pass seed-bed cultivation system, but selects from four or five different cultivator or disc-based tools available to achieve the required tilth - depending on the field and soil conditions.
A decent seedbed helps with rapid crop emergence where drilling is delayed for ryegrass control, along with buried surface trash ensuring the best possible control from a Defy + flufenacet based pre-emergence autumn herbicide programme.
Application technique, with higher water volume and 90% drift reduction nozzle selection, is seen as essential to improve results.
That usually proves sufficient for grassweed control, including black-grass where there is no history of resistance on the farm and has been effectively managed with the whole ICM approach.
Autumn oilseed rape still provides a valuable opportunity to target ryegrass with different herbicide chemistry options, with spring cropping is another important tool.
All the ground for Rob Burden’s spring cropping is ploughed, with the intention of burying grass weed seeds. But he is also conscious that it could bring previously buried dormant ryegrass seed back to the surface, so it has to be combined with cultivations and stale seedbed to kill off weeds.
Increasingly he is looking to cultivation techniques to remove weed seedlings in spring, to avoid an over reliance on repeated glyphosate applications.
“The fewer glyphosate treatments we can make the better, if the experience of other herbicide resistance issues is to be avoided,” he argued.
The viability of ryegrass does depend on soil conditions, but buried ryegrass would typically remain viable for less time than black-grass. That makes rotational ploughing especially useful, and maybe an even more important tool in ryegrass control.
Spring barley been introduced into the rotation to give another big hit on ryegrass, initially focused on the worst affected fields. Rob also uses variable rate seeding, according to maps of target ryegrass hotspots, to increase competition and shade out weeds. Linseed is grown, but restricted to one year in nine.
So the search is on for a viable alternative spring crop that could be perform consistently for the farm, as well as help to push out the interval between OSR crops. Peas have been traditional for the area, but reliability is a problem and combining is frequently a serious challenge. Soya has been tried, but the Fumitory weed burden that rapidly developed saw the crop quickly shelved.
More recently, cover crops have been introduced that he believes could help to out-compete ryegrass populations and add valuable organic matter to soils. With a legacy of high nutrient indices from the farm’s livestock, the cover crops also help to protect the inherent fertility, he pointed out. A mix of oil radish, phacelia, vetch and spring oats had proven effective so far.
He will rogue patches of ryegrass when the workload permits, but plants are particularly difficult to pull out ‘root and all’ if it is to be successful. Where patches are more extensive, crop areas will be sacrificed to burn out the ryegrass infestation. In both instances the aim is to get plants removed before they flower.
By undertaking all the farm’s spraying, Rob feels that he has a good picture of where the infestations are and if they are continuing to spread. However, he recently had some fields flown over with a drone, and is keen to build up a visual record of population growth, or decline. He is also looking at mapping on the combine.
The integrated approach is working, however as he highlights, it does require constant attention on every aspect. “There’s no single solution, but we appreciate the renewed focus on ryegrass, and the research to develop new techniques, which we can hopefully adopt as practical tools.”