White clover can cut fertiliser need
CEREAL crops, particularly those grown for forage, can require fewer applications of fertilisers and pesticides when planted alongside white clover.
This could deliver environmental benefits, says Bob Clements, of the Institute of Grassland and Environmental Research, North Wyke, Devon, who has been examining the bi-crop with Guy Donaldson, of the Long Ashton Research Station. But the system is not appropriate for spring-sown cereals, which face too much competition from the clover.
Dr Clements says the bi-crop involves establishing a sward of white clover, then grazing or cutting for silage before drilling cereal into it. Clover is perennial, so it thrives after cereal is harvested, ready for the next cycle.
"Bi-cropping works because clover, like other legumes, captures nitrogen from the air. Some of this nitrogen is transferred into the cereal crop, reducing the need to apply fertiliser," says Dr Clements.
Less insecticide is often needed too, because aphid numbers are relatively low and the viral diseases they spread are less prominent. One possible reason for this is the presence of more predators, including beetles and spiders, in the crop.
Broad-leaved weeds cause few problems in the bi-cropping system, but herbicide treatments are sometimes needed to deal with grass weeds. But fungicide applications can often be reduced, because clover interferes with the spread of fungal diseases dispersed by splashing rain.
EU and DEFRA-funded research shows when cereal is grown for silage, yields are similar to those obtained under conventional cultivation, but fewer expensive chemicals are used, he adds. *