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Liquid digestate and min-till help farm get to carbon neutral

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Richard Anthony has achieved carbon neutral agriculture using liquid digestate, cover crops and minimal tillage on his farm in South Wales, and is now looking to sequester even more carbon dioxide.

The digestate is treated as a liquid fertilizer on the farm, the fast growing cover crops absorb carbon during the winter and the tillage shifts to no-till, while the organic matter in the soil increases sharply, holding back even more carbon in the soil.

However, it is not resting on its laurels, with companion crops being tested to reduce nitrogen use in wheat and rapeseed, while lupines grown without the need for nitrogen are tried to supply a local market. feed for cattle in Wales.

β€œWe aim to produce food, but in an environmentally friendly way, and becoming carbon neutral is the right thing to do,” he said. Farmers Weekly.

See also: How to properly store, measure and sell carbon on the farm

Farm facts

  • R&L Anthony, Tythegston Farm, Bridgend
  • Exploitation of more than 1,200 ha of land owned, leased and leased
  • The main crops include winter wheat (440 ha), rapeseed (200 ha) and maize (300 ha), with grasslands and a small area of ​​winter barley
  • Sheep – Herd of 800 Llyn crossbred ewes

High soil organic matter

All of this helps sequester over 21,000 tonnes of carbon dioxide on the farm each year, and the resulting high levels of soil organic matter of 7-8% help hold the carbon in place.

This is done while growing 10 t / ha of winter wheat, rapeseed which averaged over 5 t / ha in the summer of 2021 and large corn silage crops for the surrounding dairy farms.

β€œWe grow crops that take up carbon dioxide, which is then trapped in the soil, which improves organic matter levels,” he says.

Mr Anthony operates a farm with his wife Lyn and their son David – who runs the outsourcing business – at Tythegston Farm, halfway between Bridgend and Porthcawl, near the South Wales coast .

The soils range from heavy moist clays to pure sands.

Carbon neutral travel

The journey to reducing carbon emissions began with a mission to improve soil health about 15 years ago by signing a long-term contract to use digestate from an anaerobic digestion plant on the edge of the farm.

The municipal plant uses household food waste and thus produces a very homogeneous product for use as fertilizer, which forms the mainstay of the nutritional needs of the farm’s main winter wheat, rapeseed and corn crops.

Mr Anthony’s farm manager Dan Moore explains that inorganic fertilizers often account for 25% of carbon emissions from arable farms, and they have managed to reduce that figure in Tythegston to 2%.

Feed wheat generally receives an early dose of bagged fertilizer to provide 20-30 kg / ha of nitrogen plus some sulfur in early March, followed by two main applications of digestate at the end of the tiller (GS30) and at the start of Stem Extension (GS32) provide a total nitrogen to the crop of 250-260kg / ha.

Graham is the farm’s main wheat variety, grown for reliability, while the Extase miller variety is grown for animal feed and was bred for its excellent resistance to septoria, a disease caused by wet weather.

Carbon sequestration

The use of digestate with turkey litter, compost and the effect of sheep grazing has helped bring soil organic matter to an impressive 7-8% from 2-3% previously, helping to sequester even more carbon.

The digestate can be stored in three large lagoons on the farm and then spread through an umbilical pipeline system, with two dribbler tankers also in use.

Another key factor in limiting carbon emissions is to always have a soil crop, and a mix of forage rye / Westerwolds ryegrass cover crop is used during the winter before a corn crop sown in the spring. .

This fast growing cover crop provides good ground cover during an often wet Welsh winter, and can then be cut or grazed by sheep before sowing corn in the spring.

Catch crops

In order to keep the soil covered year round, rapeseed stubble is grown with a TopDown tine and disc, with a seeder attached to provide a quick catch crop of phacelia which is grown for about four to six weeks before winter. wheat is sown there in the fall.

β€œWheat crops after phacelia look very green, and it’s remarkable how phacelia retains nitrogen in the soil,” says Anthony.

Wheat grown after phacelia also lowers cultivation costs, as wheat can be sown directly into the spray phacelia, whereas before it required another pass of the TopDown cultivator before sowing the wheat.

β€œThe rooting of phacelia is amazing. If you dig it up there’s a big root system filled with worms, ”says Moore, who adds that omitting a top-to-bottom passage saves Β£ 58 / ha in seed cost. of catch crops at Β£ 10-12 / Ha.

Next season, the farm will try adding vetch to the catch crop mix, as it is hoped that including the legume will fix some nitrogen to help young wheat plants.

Companion rapeseed crops

Companion rapeseed crops, originally designed to keep flea beetles away from cabbage stems, have also proved invaluable in the quest to reduce nitrogen fertilizer levels.

The farm developed a one-pass planting technique using a Mzuri planter to sow spring beans relatively deeply, then rapeseed and buckwheat at a shallower depth, with the vetch then spread behind.

Beans and vetch being legumes help fix nitrogen, while buckwheat extracts phosphate, and this technique has the potential to reduce nitrogen from the 150-200 kg / ha used from digestate and bagged product. .

Chris Taylor, local agronomist for the Agrii advisory group, explains that the use of companion crops in on-farm trials has shown that nitrogen levels can be reduced by 30 kg / ha for rapeseed.

Direct drilling movement

Tillage is reduced on the farm to avoid carbon emissions and the goal is to try and switch to more direct seeding, but this process is difficult with difficult soils and high annual rainfall of 1250mm. Currently, rapeseed is directly sown, while the establishment of wheat is largely minimum tillage.

The result is that the entire farm sequesters 21,303.48 t of carbon dioxide per year, using the Farm Carbon Toolkit calculation method.

The success could be overshadowed by a decision by the Welsh government to include all of Wales in an area vulnerable to nitrates, as this would limit the amount of organic digestate they could apply to winter wheat to 170 kg / Ha.

But that would be counterproductive, because if it were to become law, it would cause the farm to use more bagged fertilizer, which has an extremely high carbon footprint due to being produced by a high-energy industry.

Undergrowth crops

Meanwhile, the farm is looking to cut more emissions by growing wheat with an understory of ryegrass and clover to reduce the need for fertilizer and herbicides, and the benefits may even survive to help a next harvest. rapeseed.

A mixture of two year old Italian ryegrass and white clover was drilled this fall, which will be grazed or cut next year, then sprinkled with low glyphosate, and strip-till soil sown with wheat in autumn.

Mr Taylor is also looking at the performance of new legume crops in South Wales, as despite good growth of beans on the farm, they do not produce enough protein to compete with soybeans.

He looked at chickpeas, lupines and white beans. A lupine crop gave 3.5 t / ha without inputs last season, so he favors this legume crop, and the area under lupine crops will increase next spring.

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