New modelling led by Rothamsted Research shows that a ban on glyphosate could lead to an increase in weed abundance and a decrease in the yields of some crops.
Although the environmental risks associated with the herbicide would be eased, alternative approaches to weed control had mixed outcomes for the environment, food production and profitability, although some show potential benefits. Weed communities with evolved resistance to non-glyphosate herbicides were not projected to be disproportionately affected by removing glyphosate, despite the lack of alternative herbicidal control options.
“Our findings emphasise the need for careful consideration of trade-offs if a ban were to be enacted,” said Rothamsted’s Dr Helen Metcalfe who led the study. “Glyphosate, the most widely used herbicide, is linked with environmental harm and possible human health issues, but it’s use is central to no-till farming approaches. Public pressure is now building for it to be replaced in agricultural systems. We wanted to find out what the implications of a ban might be.”
Glyphosate is becoming increasingly important as part of regenerative agricultural practices where it is used for weed control in no-till stubbles and the management of cover crops and leys. The new work shows that environmental and health issues associated with glyphosate may trade-off against some of the benefits of moving to more sustainable systems that reduce tillage and integrate cover crops.
Crop rotations with more spring cereals or grass leys for weed control increased arable plant diversity compared to simpler rotations using glyphosate but produced less food. An increase in spring cropping also increased environmental risks associated with herbicides due to the high toxicity and bio-availability of chemicals typically applied in these crops.
“Integrated Weed Management with more use of cultural control methods offers the potential to reduce chemical use but is sensitive to seasonal variability and can also have some negative environmental and economic impacts,” said Dr Metcalfe. “The uncertainty associated with the non-chemical approaches we tested supports the view that adoption of IWM requires multiple options adapted to the local environment. This will however require careful consideration and a strong founding in the principles of weed ecology and biology.”
The study team hope that the modelling exercise will encourage more farmers to experiment with alternative weed control strategies. “Many farmers are beginning to investigate how they can best control weeds with fewer herbicides. Simulation studies like this one can help to carefully assess any management changes, as it is not always possible to predict outcomes when so many variables – including the weather – are playing a key role,” said Dr Metcalfe.
