1 December 1995

Early weed control vital to energy crop

ENERGY crop growers will have to pay particular attention to early weed control if they want speedy returns, according to poster presentations.

Trees such as willow and poplar are very sensitive to weed competition in their establishment year, said David Clay of Avon Vegetation Research. Uncontrolled weeds can cut first year growth by 95%.

Trials near Bristol examining a range of options, including the use of cover crops, suggest a "stale seed-bed" approach followed by inter-row weeding may be the best low-input strategy.

Using cover crops pre-planting is environmentally attractive because it helps prevent nitrogen leaching, Mr Clay explained. But even when that cover is destroyed by glyphosate, the resulting spring weed control is not as good as from using a residual herbicide mix or a stale seed-bed technique.

Slugs encouraged by the decaying vegetation can also be a "serious problem", their control adding to the cost of the cover crop approach.

Miscanthus growers must keep on top of weeds after they have planted, but so far there are no on- or off-label approved chemicals for the crop, according to ADASs Mike Bullard.

"You must control weeds in the first season or youll get a yield penalty year on year," he said. Mechanical control is "quite feasible" given the widely spaced, even plantings.

ADAS and Danish work shows there is a wide range of herbicides, including many cereal weedkillers, which could be used on the crop. Atrazine is also a possibility.

Once established it should be fairly easy to keep stands clean with a combination of post-harvest broad-spectrum sprays and spring-applied selective materials, he said.

In time weed problems may become less severe as the seed-bed under the perennial heavily shading crop becomes "stale", he added.