A guide to low carbon farming

Agri­cul­ture is a contrib­utor to green­house gas emis­sions world­wide, but the adop­tion of low carbon prac­tices can turn this around.

Over the past 200 years farming has released carbon dioxide into the atmos­phere, explains Tom Tolputt, mixed farmer and consul­tant. “Modern farming prac­tices such as deep tillage, fertiliser and pesti­cide appli­ca­tion release a lot of green­house gases. Nitrogen fertiliser produc­tion is very carbon dioxide heavy and a recent study has shown it actu­ally burns carbon out of the soil.”

However, there are ways of building soil health and organic matter such as reducing tillage, changing grazing prac­tices, intro­ducing peren­nial species into arable rota­tions, and limiting the use of harmful chem­i­cals.

If we can put 0.1% of organic matter back into the soil a year, this will sequester 8.9t/ha a year of carbon back into our soils.

“If we can put 0.1% of organic matter back into the soil a year, this will sequester 8.9t/ha a year of carbon back into our soils,” says Mr Tolputt. “Which also builds the ability to access and hold nutri­ents and will also improve soil biology and drought resis­tance.”

Step 1: Reduce tillage impact

Ploughing and deep tillage bring soil to the surface. “In this process carbon is released from the soil to the air and the envi­ron­ment for the mycor­rhizal is destroyed.”

Reducing tillage keeps the mycor­rhizal in place to func­tion and mobilise phos­phate to the plant. “If there is a need for ploughing in a rota­tion apply a mixture of molasses, mycor­rhiza, tricho­derma and bacteria as a spray on an estab­lished seedbed to encourage good biolog­ical activity in the soil. This will give the bacteria and fungi a food source to repop­u­late the soil and help the soil biology.”

A soil pit should be dug to estab­lish compaction levels and then subse­quently every three years to under­stand the impact of the reduc­tion of tillage. “The move to reduced or zero till in conven­tional systems will help in preserving soil carbon.”

Step 2: Reduce bare soils

Growing cover crops or keeping a crop growing in the soil at all times keeps the soil biology alive. “It’s not a well-known fact but each plant pushes down 30-40% of the energy it photo­syn­the­sises in the form of root exudate – which is full of nutri­ents and feeds the soil biology. With bare ground the bacteria in the soil are not being fed, and so start to die off release carbon.”

Cover crops include; phacelia, alsike clover, daikon radish, oats, berseem clover, vetch and rye.

Step 3: Maximise diver­sity

The more diver­sity above the soil is rela­tive to the number of ecosys­tems being fed in the soil.

“There are no mono­cul­tures in nature and different plants will support different bacteria in the soil – for example bras­sicas don’t support mycor­rhiza in the soil very well, whereas oats or peren­nial crops do.

Also deep rooting crops like cocks­foot or chicory will push sugars and exudates further into the soil and support more ecosys­tems as well as seques­tering carbon.

As a signif­i­cant amount of a plant’s energy is returned back to the soil, this helps support the bacte­rial and fungal networks which then provide nutri­ents back to the plant; a form of symbiosis.”

A diverse ley will provide different levels of the soil with nutri­ents.

Step 4: Minimise detri­mental prac­tices

Detri­mental prac­tices including heavy culti­va­tions, spraying fertiliser in high doses such as urea or ammonia – these should be avoided. Try to make sure the nitrogen used is slower release; nitrogen sulphate or combined with a source of humate or alter­na­tively substi­tuted for liquid appli­ca­tions. “The appli­ca­tion of urea or harmful forms of nitrogen can effect on the soil carbon and bacteria.”

Step 5: Growing crops suit­able to climate

Tailoring the rota­tion to the local climate means crops require fewer inputs to grow success­fully, advises Mr Tolputt. “For example wheat is more suited to drier climates and fodder beat and oats are more suited to a costal envi­ron­ment.”

Step 6: Consider animals in the rota­tion

A more tradi­tional rota­tion involves grazing animals on peren­nial crops. “These deep rooting crops help to build soil biology, soil nitrogen and sequester carbon – this reduces the amount of nitrogen required for the next crop.”

Holistic grazing, where animals are rota­tion­ally grazed and moved onto a new paddock every 24-72 hours, creates a symbi­otic rela­tion­ship in which the animals graze, digest and defe­cate – providing nutri­ents and bacteria back to the soil.

“The plants provide energy, through their root systems to the soil, the soil provides minerals to the plants and the plant provides food for the animal. The rest period allows time for the plants to regrow and improve their root system, allowing more carbon to be sequestered into the soil.”

Typical crops which could be included for a grazing ley are, cocks­foot, chicory, plan­tain, red and white clover and trefoil. “Including these mixes in grazing or cutting leys will increase drought toler­ance and increase carbon seques­tra­tion within the soil, adding to a greater poten­tial carbon benefit.”

Further infor­ma­tion