Miscanthus could cut blackgrass and improve soils

Attractive 10-year contracts are now on offer to grow biomass crop miscanthus and could provide a viable option for growers looking to rid problem fields of blackgrass.

Growing miscanthus fell out of favour after a collapse in demand for biomass and a lack of infrastructure for processing the crop, giving way to the rise of other renewable energy sources such as anaerobic digestion (AD) fed by crops such as forage maize.

However, demand for biomass used in commercial and domestic energy generation is on the rise once more and has led to new opportunities to grow the crop.

Terravesta processes about two-thirds of the national crop – estimated at 8,000ha – into pellets that feed biomass plants and is offering growers 10-year fixed-term contracts linked to the retail price index.

See also: Farm power – Weigh up your renewables options

John Reade, principal lecturer and weed expert at Harper Adams University, says that in extreme cases of blackgrass infestation, taking the land out of combinable crop production is the best way of reducing the weed burden.

Three-year grass leys would be a more conventional way of doing that, but unless growers have a livestock outlet for the forage, it isn’t a viable option.

Dr Reade adds that with a market, miscanthus would be ideal to supress the weed and reduce viable seed in the soil over the period of the contract.

“Blackgrass can remain viable in the soil for three to four years and in the most extreme cases, up to seven years.

“I’m not aware of anyone planting miscanthus for blackgrass control, but in theory if you put a problem field into the crop for 10 years, when you come back to it, you shouldn’t have an issue with blackgrass anymore.”

Soil conditioner

Harvested for its tough cane, the plants’ leaves drop to the floor each year and result in a think mulch developing on the soil surface, creating a valuable boost to soil organic matter.

“You aren’t ploughing or cultivating either, so the soil goes undisturbed for a long period and you would see an increase in worm activity.

“One thing you would have to bear in mind is when the ground comes out of miscanthus production, you might have a problem with rhizomes growing in the following crop and can be tricky to remove,” explains Dr Reade.

There are agronomic benefits to growing the crop, but does the financial side of the story stack up?

In the past, now defunct companies offered contracts that weren’t fulfilled as the expected market demand from power stations never materialised. There was also limited variety choice and yields were sometimes poor.

With that still relatively fresh in the memory, growers might have doubts about such a long-term commitment to growing the crop.

Financial security

Looking to reassure potential growers is Terravesta general manager George Robinson, who says their contract offer would provide a guaranteed revenue stream over the 10-year period.

They now have supply agreements with national power generators and are working to build supply relationships on a more local level with users such as poultry farmers.

“There isn’t a huge amount of confidence in commodities at the moment and the sector is leaning heavily on land values and borrowing.

“Miscanthus can offer security on at least a proportion of your land and although the scientific evidence isn’t there, blackgrass would become insignificant after 10 years and it could help regenerate soils,” says Mr Robinson.

Low input

Planting is carried out with a specialist planter and establishment costs are about £1,050/ha based on a 15ha area at a plant population of 5,000 plants/ha, although that cost will fall with larger areas.

The crop is planted from early April to mid-May and except for weed control in the previous autumn and pre-planting in the spring and small amounts of early nitrogen, requires very little input.

The crop is typically chopped and baled in March or April and in the first two years sees very little return, but by year three the crop should be yielding about 70% of its full potential, which is in the region of 13-15t/ha on good land.

The 2015-16 contract price is about £73.80/t, with barn-stored bales at <16% stored until the end of August fetching a £1/t “barn bonus” and bales stored beyond August a £2/t premium and there are opportunities to grow the crop across the country.

Mr Robinson says net returns over the period of the contract would be in the region of £528/ha, compared with about £68/ha for combinable crops over the same period.

“That is a huge difference and there is no reason why miscanthus can’t become part of conventional rotations,” he adds.