A perennial crop originally native to eastern and central America is now being marketed in NI as a credible alternative to maize, especially for use in local anaerobic digestion (AD) facilities.

Sunergy (Silphium perfoliatum) is a low-input, high-output perennial crop, which it is claimed can be grown with no fertiliser (digestate only), and once established is resistant to any major pests and diseases. It has a lifespan of up to 15 years.

The sole distributor of Sunergy in the UK is English specialist seed company Newtone Agriscapes, with Portadown-based ReCon Resources taking on the role as agent in NI and Scotland.

Speaking at a launch on Tuesday, Nick Green from Newtone Agriscapes said the crop is grown across parts of Europe for various end uses, including biogas production in Germany. If cut earlier in the season it can be incorporated in livestock diets (characteristics are similar to a 50:50 lucerne-maize mix), while it can also be used for fibre production. The first sites in the UK were planted in spring 2022, including in Wales, Kent, Sussex and Warwickshire, said Green.

Sunergy must go through a cold phase (winter) to produce a stem, so the crops planted in spring 2022 will not be harvested until next year. Traditionally in France and Germany it is sown alongside maize as a nurse crop.

The seed is small, and is planted at a rate of 3kg/ha, which gives four to five plants per m2. It is normally precision drilled, and costs around £500/kg, so seed is the biggest up-front cost.

“In NI, it might be best sown in August and September, which means you get a crop the following year. On balance, we are leaning towards autumn sowing being more beneficial,” said Green.

But once established there is no annual sowing cost, so over its lifespan the analysis presented at the event on Tuesday suggests it is much cheaper to grow than maize.

Research trials have shown that it gives 80% of the biogas yield of maize, while also significantly outperforming grass silage due to its much higher dry matter yield potential.

Sunergy grows to up to 3.6m, and has a three-month flowering phase, so is good for biodiversity, and the undisturbed root structure should mean that it is able to sequester carbon into the soil.

“It will grow across a wide range of sites, even marginal areas. Once established, it is drought tolerant and will cope with wet conditions. It is harvested in the same way as maize,” said Green.

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