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Increase soil organic matter with Miscanthus

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  • 5 min read

Rising temperatures, changing rain patterns and intensive farming practices can all lead to soil erosion, eradication of soil fertility and biodiversity loss and it’s been estimated by the Environment Agency that the annual soil erosion rate for the UK is 2.2 million tonnes of topsoil with over 17% of arable land showing signs of erosion.

Almost 4 million hectares of soil are at risk of compaction in England and Wales, affecting soil fertility and our water resources as well as increasing the risk of flooding.

Looking after our soil for future generations is rightly a top priority, and while there are many more techniques employed to preserve it, Miscanthus can play an important role in improving our soil.

Scientific studies demonstrate a positive impact of Miscanthus in restoring soil health and fertility through increasing soil carbon and organic matter naturally, restoring soil life, particularly invertebrates, including earthworms, insects, soil-based organisms and micro-organisms.

Used rotationally in agricultural systems, Miscanthus reverses the severe soil degradation of intensive food production systems which will enable more sustainable, less depleting and lower cost agricultural regimes in future.

Alex Robinson, Terraveta’s operations director, says there are many factors in the crop’s life-cycle which contribute to its ability to stabilise and enrich soils.

“Miscanthus crops are harvested annually after the above ground biomass has senesced (died back). During this process, the leaves fall and accumulate on the soil surface and together with the stubble left after harvest, form a mulch. The stems are cut and baled to be used for carbon negative power generation,” explains Alex.

“Around 3 – 7 tonnes per hectare of crop debris is returned to the ground annually. This represents up to 50% of the above ground biomass.”

“The crop debris returned to the soil each year contains 1.4 – 3.2 tonnes of carbon per hectare,” he says.  “In an average clay soil of containing 1.5 – 2% soil organic matter, this is equivalent to an increase of 1.6 – 3.8% soil organic matter per year. Over 15-years a crop of Miscanthus can increase soil organic matter by up to 55%”

Alex continues “Once a Miscanthus crop has established, further cultivations are not required, which results in less soil aeration, therefore less soil organic matter is lost to the atmosphere as carbon dioxide and methane, from the action of microbes than would be from typical arable practices.”

Slow flooding

The Met Office says the UK received 109% (138.8 mm) of its average rainfall in October and farms have suffered unprecedented damage from the recent flooding.

Miscanthus can play a part in stabilising and enriching flooded soils. “Because of Miscanthus’ perennial nature, annual planting is not needed. This therefore reduces soil disturbance to a minimum promoting the action of weathering, roots and worms to enhance soil structure,” Alex.

“The structure of Miscanthus rhizome and root helps to stabilise soils, making it more resilient against flood-caused soil erosion. The crop debris on the soil surface also helps water infiltration and reduces water run-off.

“As a solution to land that is becoming increasingly unlikely to planted with arable crops this year, Miscanthus is a very profitable option.”

Increase profitability

Miscanthus is a long-term crop, with index-linked fixed price returns, and numerous growing end-markets. Terravesta develops novel Miscanthus supply chains to replace fossil derived feedstocks for heat, energy, fuels, compostable plastics, pharmaceuticals, agri-products and other bio-economic uses.

The Department for Business, Energy and Industrial Strategy (BEIS) has a target of 1.4 million ha of perennial biomass crops to be planted in the UK and has calculated that this is sustainable, without posing a risk to food production.

To put this into perspective, this is around 14% of the arable cropping area in the UK, which is equal to the area for set-aside in the UK.

Terravesta Athena™

We launched Terravesta Athena™ in June 2019, which is the world’s first commercially bred Miscanthus hybrid variety, boasting a much faster establishment and quicker yield ramp up, improving grower return on investment.

The new variety delivers staggering results in commercial-scale trials, meaning quicker and higher returns to farmers and more than double the energy per hectare.

Terravesta Athena™ produces higher yields in year two of the crop’s 20-year life cycle, an average mature yield double that of original Miscanthus giganteus, a calorific value increase of 12.2%, resulting in a 220% increase in energy per hectare (megajoules), and a significant ash content reduction, all of which benefits the end market significantly.

Commercial-scale trials show that on average year two yields are 62% above the standard Miscanthus giganteus variety, producing 8t/ha for the first harvest and 12.5 t/ha in year three. Extensive testing for Athena took place on 270ha of varied UK soil types, as well as differing geographic and climatic conditions.

Miscanthus facts

  • Miscanthus is a low input biomass energy crop, requiring little or no nitrogen fertiliser inputs, and thrives on poor grade, flood or drought prone marginal land
  • Miscanthus offers significantly higher than average arable returns with an average margin of £558/ha each year, over a 15-year period
  • The crop is currently grown from rhizome (root stock), that’s planted once, harvested in the spring and has annual