DSV is investigating whether undersowing oilseed rape crops with pulses cuts growing costs by reducing the need for fertilisers and pesticides.
About 1% of French farmers have adopted the approach and claimed three key cost savings, explained Alexander Doering, product manager at DSV.
First, the legume companion crops fix nitrogen and enables farmers to cut nitrogen fertiliser use by about 30kg/ha, but he stressed that trials are needed to confirm this.
“It is not clear if nitrogen is released at the right time or is too late for the oilseed rape crop to use it to increase yields. It is typically available in late spring early summer.”
Second, farmers claim it reduces weeds and, therefore, reduces herbicide requirements. Third, farmers have reported less insect damage in the autumn, which is valuable given the flea beetle risk.
But Dr Doering, who did a PhD looking at insects and oilseed rape, says there is no real data showing it works.
This has prompted DSV to trial different options to answer several key practical questions. For example, how does it fit in with herbicide programmes, allowing farmers to control certain weeds without taking out the companion crop?
“Also how does it cope in different years, as some years the oilseed rape will too competitive while in others, the companion crop may be too competitive. Finally, what species do you use?
“We know that non-legumes are too competitive, but which legumes are the best?”
And the most important of all, it needs to offer an economic benefit to farmers. “Does the reduction in herbicide, fertiliser and insecticide need to cover the expense of the seed,” he said.